Breathing and Exchange of Gases

Topic: Respiratory System; Subtopic: Neural Regulation of Respiration

Keyword Definitions:

• Chemosensitive area: Region near the medullary respiratory center sensitive to chemical changes in blood, regulating respiration rate.

• Rhythm center: Medullary respiratory center that generates the basic rhythm of breathing.

• Medulla: Part of the brainstem that contains centers controlling involuntary functions, including respiration and cardiovascular activity.

• CO2: Carbon dioxide, a byproduct of cellular respiration, detected by chemoreceptors to modulate breathing.

• O2: Oxygen, essential for cellular respiration, monitored by peripheral chemoreceptors for hypoxia detection.

• HCO3-: Bicarbonate ion, a buffer in blood that indirectly influences respiratory rate by affecting pH.

• N2: Nitrogen, an inert gas, does not significantly affect chemosensitive respiratory regulation.

• Peripheral chemoreceptors: Receptors in carotid and aortic bodies that detect O2, CO2, and pH changes.

• Respiratory control: Neural and chemical mechanisms maintaining homeostasis of blood gases.

• Homeostasis: Physiological maintenance of stable internal conditions, including blood gases.

• pH regulation: Control of hydrogen ion concentration in blood, influencing respiratory rate via central and peripheral chemoreceptors.

Lead Question - 2022 (Abroad)

In the regulation of respiration, a chemosensitive area adjacent to the rhythm centre in the medulla region of the brain, is highly sensitive to:

1. HCO3-

2. CO2

3. O2

4. N2

Explanation: The chemosensitive area near the medullary rhythm center detects changes in CO2 levels in arterial blood. Elevated CO2 increases H+ concentration, lowering pH, which stimulates the central chemoreceptors to increase the rate and depth of respiration. This mechanism maintains homeostasis of blood gases. O2 is monitored mainly by peripheral chemoreceptors, HCO3- indirectly influences pH, and N2 has negligible effect. Proper function of this area is vital for normal respiratory control and acid-base balance. Correct answer: 2

1. SINGLE CORRECT ANSWER MCQ

Which gas primarily stimulates central chemoreceptors in the medulla to control breathing?

1. O2

2. CO2

3. HCO3-

4. N2

Explanation: Central chemoreceptors in the medulla respond primarily to CO2 levels. CO2 diffuses into cerebrospinal fluid, forming H+ ions that lower pH and trigger increased respiration. O2 is mainly detected by peripheral chemoreceptors, HCO3- indirectly affects pH, and N2 is physiologically inert. This feedback system is crucial for maintaining acid-base balance and normal respiratory rate. Correct answer: 2

2. SINGLE CORRECT ANSWER MCQ

Peripheral chemoreceptors primarily monitor:

1. CO2

2. O2

3. HCO3-

4. N2

Explanation: Peripheral chemoreceptors in carotid and aortic bodies respond mainly to hypoxia (low O2) in arterial blood. They also respond to CO2 and pH changes to a lesser degree. HCO3- indirectly affects chemoreceptor activity, and N2 does not stimulate them. These receptors provide rapid feedback to adjust respiration rate and maintain oxygen homeostasis. Correct answer: 2

3. SINGLE CORRECT ANSWER MCQ

An increase in arterial CO2 leads to:

1. Decreased respiratory rate

2. Increased respiratory rate

3. No change in breathing

4. Only peripheral vasodilation

Explanation: Elevated arterial CO2 increases H+ concentration, stimulating central chemoreceptors in the medulla. This triggers an increase in both rate and depth of respiration, enhancing CO2 removal and restoring pH. Peripheral chemoreceptors contribute minimally, and N2 does not affect breathing. This mechanism maintains homeostasis of blood gases and acid-base balance. Correct answer: 2

4. SINGLE CORRECT ANSWER MCQ

Which region of the medulla generates the basic rhythm of respiration?

1. Apneustic center

2. Pneumotaxic center

3. Rhythm center

4. Hypothalamus

Explanation: The rhythm center in the medulla, specifically the dorsal and ventral respiratory groups, generates the basic rhythm of breathing. It receives input from central chemoreceptors monitoring CO2 and pH. The apneustic and pneumotaxic centers in the pons modulate rhythm, while the hypothalamus regulates breathing during emotional or temperature changes. Proper function ensures steady ventilation matching metabolic demands. Correct answer: 3

5. SINGLE CORRECT ANSWER MCQ

Which ion indirectly affects central chemoreceptor activity in the medulla?

1. HCO3-

2. Cl-

3. K+

4. Na+

Explanation: HCO3- (bicarbonate) indirectly influences central chemoreceptors by buffering pH changes. Elevated CO2 increases H+ and decreases pH, triggering increased ventilation. Central chemoreceptors detect H+ in cerebrospinal fluid. Other ions like Cl-, K+, and Na+ do not directly regulate respiratory chemoreception. This mechanism maintains acid-base balance and proper oxygen-carbon dioxide homeostasis. Correct answer: 1

6. SINGLE CORRECT ANSWER MCQ

The primary stimulus for increasing ventilation under normal conditions is:

1. Low O2

2. High CO2

3. Low N2

4. High HCO3-

Explanation: High CO2 in blood is the primary stimulus for increasing ventilation under normal physiological conditions. Central chemoreceptors in the medulla detect CO2-induced pH changes, prompting increased breathing to restore homeostasis. Low O2 stimulates peripheral chemoreceptors only in hypoxic conditions. N2 is inert, and HCO3- indirectly affects pH but is not the primary stimulus. Correct answer: 2

7. ASSERTION-REASON MCQ

Assertion (A): Central chemoreceptors respond primarily to CO2 in arterial blood.

Reason (R): Increased CO2 lowers pH in cerebrospinal fluid, stimulating respiration.

1. Both A and R are true and R explains A

2. Both A and R are true but R does not explain A

3. A is true but R is false

4. A is false but R is true

Explanation: Central chemoreceptors in the medulla detect CO2-induced pH changes in cerebrospinal fluid. Elevated CO2 produces H+ ions, lowering pH, which directly stimulates the chemoreceptors to increase respiratory rate and depth. Both Assertion and Reason are true, and the Reason explains the mechanism of central CO2 sensitivity. This system is essential for maintaining acid-base balance and proper oxygen-carbon dioxide homeostasis. Correct answer: 1

8. MATCHING TYPE MCQ

Match the following structures with their respiratory function:

Column A:

1. Medullary chemoreceptors

2. Peripheral chemoreceptors

3. Pneumotaxic center

4. Apneustic center

Column B:

1. Respond to CO2 and pH

2. Respond to O2 and pH

3. Inhibits inspiration, controls rate

4. Promotes inspiration, prolongs inhalation

Explanation: Correct matching: Medullary chemoreceptors → Respond to CO2 and pH, Peripheral chemoreceptors → Respond to O2 and pH, Pneumotaxic center → Inhibits inspiration and controls rate, Apneustic center → Promotes inspiration and prolongs inhalation. These centers coordinate breathing rhythm and maintain homeostasis of blood gases. Correct answer: 1-A, 2-B, 3-C, 4-D

9. FILL IN THE BLANKS / COMPLETION MCQ

The central chemoreceptors detect changes in _______ to regulate respiration.

1. O2

2. CO2

3. N2

4. H2O

Explanation: Central chemoreceptors in the medulla monitor CO2 levels indirectly via H+ ions in cerebrospinal fluid. Elevated CO2 lowers pH, triggering increased ventilation. Oxygen is primarily sensed by peripheral chemoreceptors, while N2 and H2O have negligible effects on central chemoreceptors. This mechanism maintains blood gas homeostasis and acid-base balance. Correct answer: 2

10. CHOOSE THE CORRECT STATEMENTS MCQ

Statement I: Central chemoreceptors respond mainly to CO2 levels.
Statement II: Peripheral chemoreceptors respond mainly to O2 levels.

1. Only Statement I is correct

2. Only Statement II is correct

3. Both Statements I and II are correct

4. Both Statements I and II are incorrect

Explanation: Central chemoreceptors detect CO2-induced pH changes in cerebrospinal fluid, while peripheral chemoreceptors in carotid and aortic bodies respond primarily to low O2. Both mechanisms work together to regulate ventilation and maintain homeostasis. Understanding the distinction between central and peripheral chemoreceptors is crucial for respiratory physiology. Correct answer: 3

Topic: Respiratory Disorders; Subtopic: Alveolar Damage and Gas Exchange

Keyword Definitions:

• Emphysema: A chronic lung disease where alveolar walls are damaged, reducing respiratory surface and impairing gas exchange.

• Alveoli: Tiny air sacs in the lungs where gas exchange occurs between air and blood.

• Respiratory Surface: Area in the lungs available for oxygen and carbon dioxide exchange.

• Asthma: A condition characterized by constriction of bronchi, causing difficulty in breathing but not destruction of alveoli.

• Bronchitis: Inflammation of the bronchial tubes, leading to cough and mucus production, but alveolar walls remain intact.

Lead Question - 2022 (Abroad)
Which of the following disorders represents decrease in respiratory surface due to damaged alveolar walls?
1. Hypocapnia
2. Bronchitis
3. Asthma
4. Emphysema
Explanation: Emphysema is a chronic lung disease characterized by destruction of alveolar walls, leading to a significant reduction in respiratory surface area. This decreases oxygen diffusion capacity, resulting in breathlessness and hypoxia. Unlike asthma or bronchitis, which involve airway constriction or inflammation, emphysema directly reduces the alveolar area, impairing gas exchange efficiency. Risk factors include smoking, air pollution, and genetic predisposition. The condition is progressive and irreversible, highlighting the importance of early prevention and management. It is a prime example of how structural damage to alveoli affects respiratory function.

1. Single Correct Answer Type:
Which symptom is most associated with emphysema?
1. Wheezing
2. Chronic breathlessness
3. Productive cough
4. Fever
Explanation: The hallmark symptom of emphysema is chronic breathlessness due to reduced alveolar surface and impaired oxygen exchange. Unlike bronchitis, which produces cough and mucus, or asthma with wheezing, emphysema primarily affects gas diffusion. Over time, patients may develop barrel-shaped chest and hyperinflated lungs, reflecting air trapping and loss of elasticity in alveoli.

2. Single Correct Answer Type:
Which of the following is a major risk factor for emphysema?
1. Sedentary lifestyle
2. Smoking
3. Viral infections
4. Excessive exercise
Explanation: Smoking is the most significant risk factor for emphysema. Tobacco smoke damages alveolar walls, causing destruction of respiratory surface. Chronic exposure leads to inflammation, elastin degradation, and progressive airflow limitation. Other factors like air pollution and genetic deficiencies (alpha-1 antitrypsin deficiency) can contribute, but smoking remains the primary preventable cause of alveolar damage and reduced gas exchange capacity.

3. Single Correct Answer Type:
Emphysema primarily affects which part of the respiratory system?
1. Bronchi
2. Trachea
3. Alveoli
4. Nasal cavity
Explanation: Alveoli are the primary site affected in emphysema. The walls of alveoli are destroyed, reducing surface area for gas exchange. This leads to hypoxia and hypercapnia. Bronchi and trachea may remain structurally intact, though secondary airflow obstruction can occur. Damage to alveoli also reduces lung elasticity, making exhalation less efficient and contributing to the clinical features of breathlessness and hyperinflation.

4. Single Correct Answer Type:
Which diagnostic test best detects alveolar destruction in emphysema?
1. Chest X-ray
2. Spirometry
3. CT scan of lungs
4. Sputum culture
Explanation: A CT scan of lungs is most sensitive for detecting alveolar destruction in emphysema. It can visualize areas of hyperinflation, bullae formation, and loss of alveolar walls. Spirometry shows airflow limitation but cannot directly visualize alveolar damage. Early detection is critical for management, as emphysema is irreversible and progresses with continued exposure to risk factors.

5. Single Correct Answer Type:
Which physiological change occurs due to emphysema?
1. Increased oxygen diffusion
2. Reduced alveolar surface area
3. Increased mucus production
4. Bronchial constriction
Explanation: Emphysema leads to reduced alveolar surface area, impairing oxygen diffusion. As alveoli are destroyed, less respiratory surface is available for gas exchange, causing hypoxia. Mucus production and bronchial constriction are more characteristic of bronchitis and asthma. The structural loss in emphysema also reduces lung elasticity, causing air trapping and inefficient ventilation, contributing to breathlessness.

6. Single Correct Answer Type:
Which treatment is primarily used to manage emphysema symptoms?
1. Antibiotics
2. Bronchodilators and oxygen therapy
3. Antivirals
4. Steroids only
Explanation: Management of emphysema includes bronchodilators and oxygen therapy to relieve breathlessness and improve oxygenation. While structural damage is irreversible, symptom control improves quality of life. Pulmonary rehabilitation and lifestyle changes like smoking cessation are essential. Antibiotics treat infections but do not reverse alveolar destruction. Oxygen therapy compensates for decreased respiratory surface and impaired gas exchange.

7. Assertion-Reason Type:
Assertion (A): Emphysema causes reduced oxygen intake.
Reason (R): Damage to alveolar walls decreases respiratory surface area.
1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, R is false
4. A is false, R is true
Explanation: Both Assertion and Reason are true. The destruction of alveolar walls in emphysema decreases the surface area for gas exchange, leading to reduced oxygen intake and hypoxia. This direct relationship between structural damage and functional impairment explains the primary pathophysiology of emphysema, distinguishing it from other respiratory conditions like asthma or bronchitis.

8. Matching Type:
Match the respiratory disorder with its primary feature:
A. Emphysema → (i) Airway inflammation
B. Asthma → (ii) Alveolar wall destruction
C. Bronchitis → (iii) Bronchial constriction
D. Hypocapnia → (iv) Low CO₂ in blood
1. A-(ii), B-(iii), C-(i), D-(iv)
2. A-(i), B-(ii), C-(iii), D-(iv)
3. A-(iii), B-(i), C-(iv), D-(ii)
4. A-(iv), B-(ii), C-(i), D-(iii)
Explanation: Correct matching is A-(ii), B-(iii), C-(i), D-(iv). Emphysema is defined by alveolar wall destruction, asthma by bronchial constriction, bronchitis by airway inflammation and mucus production, and hypocapnia refers to decreased blood CO₂. Each disorder has distinct pathological and physiological features, helping differentiate diagnosis and management strategies.

9. Fill in the Blanks Type:
In emphysema, the reduction in _______ leads to decreased oxygen exchange.
1. Bronchial tubes
2. Alveolar surface area
3. Tracheal diameter
4. Lung compliance
Explanation: The correct answer is alveolar surface area. Destruction of alveoli in emphysema directly reduces the area available for oxygen diffusion, causing hypoxia. While lung elasticity also decreases, the primary factor limiting gas exchange is the loss of alveolar walls, which differentiates emphysema from asthma or bronchitis, where alveolar structure is largely intact.

10. Choose the Correct Statements Type:
Which of the following statements about emphysema are correct?
1.

Subtopic: Conducting and Respiratory Portions

Keyword Definitions:

• Conducting part: The portion of the respiratory tract that transports, filters, warms, and humidifies air but does not participate in gas exchange.

• Respiratory part: The portion of the system where gaseous exchange occurs, including bronchioles, alveolar ducts, and alveoli.

• Diffusion: The passive movement of gases like oxygen and carbon dioxide across the respiratory membrane.

• Alveoli: Thin-walled air sacs in lungs where exchange of gases occurs between air and blood.

• Cilia: Hair-like projections lining the respiratory passages that trap and move foreign particles out of the airway.

Lead Question – 2022
Which of the following is not the function of conducting part of respiratory system:
(1) Inhaled air is humidified
(2) Temperature of inhaled air is brought to body temperature
(3) Provides surface for diffusion of O₂ and CO₂
(4) It clears inhaled air from foreign particles

Explanation: The conducting part of the respiratory system filters, warms, and humidifies air but does not take part in gas exchange. Diffusion of O₂ and CO₂ occurs only in the respiratory zone of alveoli. Hence, the correct answer is (3) Provides surface for diffusion of O₂ and CO₂.

1. The actual exchange of gases in humans occurs in:
(1) Alveoli
(2) Trachea
(3) Bronchi
(4) Pharynx
Explanation: Gaseous exchange in humans takes place across the walls of alveoli, which are richly supplied with capillaries. Thus, the correct answer is (1) Alveoli.

2. Which structure connects the larynx to the bronchi?
(1) Trachea
(2) Pharynx
(3) Bronchioles
(4) Alveoli
Explanation: The trachea is a cartilaginous tube that connects the larynx to the bronchi and conducts air into the lungs. Therefore, the correct answer is (1) Trachea.

3. Which of the following forms the respiratory zone?
(1) Nasal cavity and trachea
(2) Bronchi and bronchioles
(3) Alveolar ducts, alveolar sacs, and alveoli
(4) Larynx and trachea
Explanation: The respiratory zone includes alveolar ducts, sacs, and alveoli, where gas exchange occurs between air and blood. The correct answer is (3).

4. Which is a part of conducting portion of human respiratory system?
(1) Alveoli
(2) Bronchioles
(3) Nasal passage
(4) Alveolar sacs
Explanation: The conducting portion includes nasal passage, pharynx, larynx, trachea, bronchi, and terminal bronchioles. Hence, the correct answer is (3) Nasal passage.

5. The respiratory membrane facilitates diffusion of gases due to:
(1) Large surface area and thin walls
(2) Ciliated epithelium
(3) Cartilaginous rings
(4) Mucous glands
Explanation: The alveolar surface provides a large area with very thin walls and moist lining, favoring diffusion of gases. Therefore, the correct answer is (1).

6. The trachea does not collapse due to:
(1) Ciliated epithelium
(2) Elastic fibres
(3) Cartilaginous rings
(4) Mucus secretion
Explanation: The trachea remains open due to the presence of C-shaped cartilaginous rings that prevent collapse during breathing. The correct answer is (3).

7. Assertion (A): The conducting part of the respiratory system purifies and humidifies air.
Reason (R): The alveoli of lungs perform the exchange of gases.
(1) Both A and R are true and R explains A
(2) Both A and R are true but R does not explain A
(3) A is true but R is false
(4) A is false but R is true
Explanation: Both statements are true but the reason describes the respiratory zone, not the conducting part. Hence, (2) Both A and R are true but R is not the correct explanation.

8. Match the following:
A. Trachea — (i) Voice production
B. Larynx — (ii) Air passage to lungs
C. Alveoli — (iii) Gas exchange
Options:
(1) A-(ii), B-(i), C-(iii)
(2) A-(i), B-(iii), C-(ii)
(3) A-(iii), B-(ii), C-(i)
(4) A-(ii), B-(iii), C-(i)
Explanation: The trachea conducts air, the larynx helps in voice production, and alveoli are the site of gas exchange. The correct answer is (1).

9. Fill in the blank:
The exchange of gases takes place in ______ part of the respiratory system.
(1) Conducting
(2) Respiratory
(3) Digestive
(4) Circulatory
Explanation: Gaseous exchange occurs in the respiratory part consisting of alveoli, alveolar ducts, and sacs. Hence, the correct answer is (2) Respiratory.

10. Choose the correct statements:
(1) Conducting part helps in gas exchange.
(2) Respiratory part only filters the air.
(3) Conducting part includes trachea and bronchi.
(4) Alveoli are part of conducting part.
Explanation: The conducting part consists of passages like trachea and bronchi that filter, warm, and humidify air before it reaches alveoli. The correct answer is (3).

Subtopic: Oxygen Transport in Blood

Keyword Definitions:
• Oxygenated Blood: Blood rich in oxygen, mainly found in arteries.
• Hemoglobin: Iron-containing protein in red blood cells that binds and transports oxygen.
• Oxygen Delivery: The amount of oxygen transported to tissues per unit volume of blood.
• Partial Pressure of Oxygen (pO2): Pressure exerted by oxygen in blood plasma.
• Arteries: Blood vessels that carry oxygenated blood from heart to tissues.
• Capillaries: Smallest blood vessels where gas exchange occurs.
• Tissues: Cells and structures that utilize oxygen for respiration.
• Oxygen Saturation: Percentage of hemoglobin binding sites occupied by oxygen.
• Red Blood Cells: Erythrocytes that carry hemoglobin and oxygen.
• Physiological Conditions: Normal body conditions without disease or abnormality.

Lead Question (2022):
Under normal physiological conditions in human beings, every 100 ml of oxygenated blood can deliver __________ ml of O2 to the tissues.
1. 5 ml
2. 4 ml
3. 10 ml
4. 2 ml

Explanation: The correct answer is 1. Under normal physiological conditions, each 100 ml of oxygenated blood delivers approximately 5 ml of oxygen to body tissues. Hemoglobin in red blood cells binds most oxygen, while a small amount is dissolved in plasma, ensuring adequate tissue respiration and energy production.

Guessed MCQs:

1. Which protein primarily carries oxygen in blood?
Options:
(a) Hemoglobin
(b) Myosin
(c) Albumin
(d) Fibrinogen
Explanation: The correct answer is (a) Hemoglobin. Hemoglobin in red blood cells binds oxygen molecules, facilitating transport from lungs to tissues. Albumin and fibrinogen are plasma proteins, while myosin is a muscle protein unrelated to oxygen transport.

2. Single Correct Answer:
Which blood vessel carries oxygenated blood to tissues?
Options:
(a) Arteries
(b) Veins
(c) Capillaries
(d) Lymphatic vessels
Explanation: The correct answer is (a) Arteries. Arteries transport oxygen-rich blood from the heart to tissues, while veins return deoxygenated blood to the heart. Capillaries allow gas exchange, and lymphatic vessels transport lymph, not oxygenated blood.

3. Assertion-Reason MCQ:
Assertion (A): Oxygen delivery to tissues depends on hemoglobin content.
Reason (R): Higher hemoglobin increases oxygen carrying capacity of blood.
Options:
(a) Both A and R are true, R explains A
(b) Both A and R are true, R does not explain A
(c) A is true, R is false
(d) A is false, R is true
Explanation: The correct answer is (a). Oxygen delivery is directly proportional to hemoglobin concentration. Higher hemoglobin increases oxygen binding and transport, ensuring adequate oxygen supply to tissues, which explains the assertion.

4. Matching Type MCQ:
Match the component with its function:
List - I List - II
(a) Hemoglobin (i) Oxygen transport
(b) Plasma (ii) Dissolved oxygen and nutrients
(c) Red blood cells (iii) Carry hemoglobin
Options:
1. a-i, b-ii, c-iii
2. a-iii, b-i, c-ii
3. a-i, b-iii, c-ii
4. a-ii, b-i, c-iii
Explanation: The correct answer is 1. Hemoglobin transports oxygen, plasma carries dissolved oxygen and nutrients, and red blood cells contain hemoglobin to facilitate oxygen delivery to tissues efficiently.

5. Single Correct Answer:
Which factor increases oxygen delivery to tissues?
Options:
(a) Higher hemoglobin concentration
(b) Lower cardiac output
(c) Decreased arterial oxygen saturation
(d) Vasoconstriction
Explanation: The correct answer is (a). Higher hemoglobin increases oxygen carrying capacity. Lower cardiac output, decreased saturation, or vasoconstriction reduces oxygen delivery to tissues, impairing cellular respiration and energy metabolism.

6. Single Correct Answer:
Which molecule carries a small portion of dissolved oxygen in blood?
Options:
(a) Plasma
(b) Hemoglobin
(c) Myoglobin
(d) Carbonic anhydrase
Explanation: The correct answer is (a) Plasma. While hemoglobin carries most oxygen, a small portion remains dissolved in plasma, contributing to oxygen delivery and partial pressure maintenance for diffusion into tissues.

7. Fill in the Blanks:
The total amount of oxygen delivered to tissues depends on hemoglobin content, oxygen saturation, and __________.
Options:
(a) Cardiac output
(b) Blood pressure
(c) Blood viscosity
(d) Respiratory rate
Explanation: The correct answer is (a) Cardiac output. Oxygen delivery equals cardiac output multiplied by arterial oxygen content. Blood pressure, viscosity, and respiratory rate indirectly influence delivery but do not directly determine the total oxygen delivered to tissues.

8. Single Correct Answer:
Which structure is the primary site of oxygen exchange?
Options:
(a) Capillaries
(b) Arteries
(c) Veins
(d) Heart chambers
Explanation: The correct answer is (a) Capillaries. Capillaries have thin walls allowing diffusion of oxygen into tissues. Arteries and veins transport blood, and heart chambers pump blood but are not sites of oxygen exchange.

9. Single Correct Answer:
What is the normal oxygen content delivered per 100 ml of oxygenated blood?
Options:
(a) 5 ml
(b) 10 ml
(c) 2 ml
(d) 8 ml
Explanation: The correct answer is (a) 5 ml. Normally, 100 ml of oxygenated blood delivers approximately 5 ml of oxygen to tissues. Hemoglobin-bound oxygen forms the majority, with a small fraction dissolved in plasma, ensuring efficient cellular respiration.

10. Choose the correct statements:
(a) Hemoglobin binds oxygen reversibly.
(b) Oxygen delivery depends on hemoglobin and cardiac output.
(c) Most oxygen in blood is dissolved in plasma.
(d) Arteries carry oxygenated blood to tissues.
Options:
1. a, b, d only
2. a, c only
3. b, c, d only
4. All statements
Explanation: The correct answer is 1. Hemoglobin binds oxygen reversibly, oxygen delivery depends on hemoglobin concentration and cardiac output, and arteries transport oxygenated blood. Most oxygen is bound to hemoglobin, not dissolved in plasma.

Topic: Respiratory Adaptations

Subtopic: High Altitude Physiology

Keyword Definitions:

• Altitude sickness: A group of symptoms like headache, breathlessness, and palpitations experienced at high altitude due to low oxygen levels.

• Atmospheric pressure: The pressure exerted by the weight of air; decreases at higher altitudes.

• Oxygen availability: The amount of oxygen present in the air; decreases as altitude increases.

• Respiratory adaptation: Physiological changes enabling organisms to survive at varying oxygen concentrations.

Lead Question - 2021

Assertion (A): A person goes to high altitude and experiences 'altitude sickness' with symptoms like breathing difficulty and heart palpitations.
Reason (R): Due to low atmospheric pressure at high altitude, the body does not get sufficient oxygen.
In the light of the above statements, choose the correct answer from the options given below.

(1) Both (A) and (R) are true but (R) is not the correct explanation of (A)
(2) (A) is true but (R) is false
(3) (A) is false but (R) is true
(4) Both (A) and (R) are true and (R) is the correct explanation of (A)

Explanation: Both assertion and reason are correct, and the reason correctly explains the assertion. At high altitude, low barometric pressure reduces oxygen availability, leading to hypoxia. This results in breathlessness and palpitations, commonly termed altitude sickness. Hence, option (4) is correct.

1. Which enzyme facilitates the conversion of carbon dioxide into bicarbonate in RBCs?
(1) Carbonic anhydrase
(2) Catalase
(3) Amylase
(4) Dehydrogenase

Explanation: Carbonic anhydrase catalyzes the rapid conversion of carbon dioxide to bicarbonate inside red blood cells. This enzyme plays a major role in transport of CO₂ and maintenance of acid-base balance. The correct answer is option (1).

2. Which structure prevents food from entering the trachea during swallowing?
(1) Epiglottis
(2) Glottis
(3) Larynx
(4) Vocal cords

Explanation: The epiglottis is a flap-like cartilaginous structure that closes the tracheal opening during swallowing. This prevents food particles from entering the respiratory tract. Hence, option (1) is correct.

3. Which lung volume increases significantly during exercise?
(1) Residual volume
(2) Inspiratory reserve volume
(3) Expiratory reserve volume
(4) Tidal volume

Explanation: During exercise, tidal volume increases to meet higher oxygen demand. More air is inhaled and exhaled per breath to facilitate efficient gas exchange. Therefore, the correct answer is option (4).

4. Which pigment has the highest affinity for oxygen?
(1) Hemocyanin
(2) Hemoglobin
(3) Myoglobin
(4) Chlorocruorin

Explanation: Myoglobin, present in muscles, has higher oxygen affinity than hemoglobin. It serves as an oxygen reservoir, facilitating release during oxygen deficiency in muscles. Thus, option (3) is correct.

5. In alveoli, gaseous exchange occurs primarily by:
(1) Active transport
(2) Simple diffusion
(3) Facilitated diffusion
(4) Osmosis

Explanation: The exchange of gases in alveoli is driven by differences in partial pressure of oxygen and carbon dioxide, allowing simple diffusion. No energy expenditure is required. Correct answer is option (2).

6. Which form carries the maximum amount of carbon dioxide in blood?
(1) Dissolved in plasma
(2) As carbaminohemoglobin
(3) As bicarbonate ions
(4) Attached to plasma proteins

Explanation: Around 70% of carbon dioxide in the blood is carried as bicarbonate ions in plasma, formed after enzymatic conversion in RBCs. Thus, option (3) is correct.

7. Assertion (A): Oxygen dissociation curve is sigmoid shaped.
Reason (R): Hemoglobin shows cooperative binding with oxygen molecules.
(1) Both A and R are true, and R explains A
(2) Both A and R are true, but R does not explain A
(3) A is true, R is false
(4) A is false, R is true

Explanation: The oxygen dissociation curve is sigmoid due to cooperative binding of oxygen with hemoglobin. Binding of one oxygen molecule increases affinity for the next, producing the S-shaped curve. Correct answer is option (1).

8. Match List-I with List-II:
List-I:
(a) Residual volume
(b) Vital capacity
(c) Inspiratory reserve volume
(d) Tidal volume
List-II:
(i) Air remaining after maximal expiration
(ii) Maximum air inspired after normal inspiration
(iii) Maximum air expelled after maximal inspiration
(iv) Normal air exchanged during breathing
Options:
(1) (a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)
(2) (a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
(3) (a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)
(4) (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)

Explanation: Residual volume is air left after maximal expiration, vital capacity is maximum volume expired after maximal inspiration, inspiratory reserve volume is maximum air inspired beyond normal inspiration, tidal volume is normal breathing volume. Correct matching is option (1).

9. Fill in the blank: The respiratory pigment in annelids like earthworm is ______.
(1) Hemoglobin
(2) Hemocyanin
(3) Hemerythrin
(4) Chlorocruorin

Explanation: Earthworms possess hemoglobin dissolved in plasma, unlike vertebrates where it is within RBCs. This pigment binds oxygen and transports it efficiently. Therefore, option (1) is correct.

10. Which of the following statements are correct?
(a) Surfactant prevents alveolar collapse.
(b) Medulla oblongata regulates breathing rhythm.
(c) Bohr’s effect enhances oxygen unloading.
(d) Carbon monoxide increases oxygen binding capacity of hemoglobin.
(1) a, b, c only
(2) b, c, d only
(3) a, c, d only
(4) a, b, d only

Explanation: Surfactant prevents alveolar collapse, medulla regulates breathing rhythm, and Bohr’s effect enhances oxygen release. Carbon monoxide, however, reduces oxygen carrying capacity by binding strongly to hemoglobin. Hence, correct answer is option (1).

Subtopic: Oxygen Transport and Hemoglobin Function

• Oxyhaemoglobin: The combination of oxygen with hemoglobin in red blood cells for transport from lungs to tissues.

• Alveoli: Tiny air sacs in the lungs where gas exchange occurs.

• pO2: Partial pressure of oxygen in blood or alveoli, influencing hemoglobin saturation.

• pCO2: Partial pressure of carbon dioxide affecting oxygen release from hemoglobin (Bohr effect).

• H+ concentration: Measure of acidity; higher H+ lowers hemoglobin affinity for oxygen.

• Temperature: Influences hemoglobin-oxygen affinity; higher temperature decreases affinity.

• Hemoglobin saturation: Percentage of hemoglobin molecules bound to oxygen.

• Bohr effect: The phenomenon where increased CO2 or H+ promotes oxygen release from hemoglobin.

• Oxygen loading: Process of hemoglobin binding oxygen in the lungs under favorable conditions.

• Oxygen unloading: Release of oxygen from hemoglobin in tissues where oxygen is needed.

• Gas exchange: Diffusion of oxygen and carbon dioxide between alveoli and blood.

Lead Question - 2021

Select the favourable conditions required for the formation of oxyhaemoglobin at the alveoli.

(1) Low pO2, high pCO2, more H+, higher temperature
(2) High pO2, high pCO2, less H+, higher temperature
(3) Low pO2, low pCO2, more H+, higher temperature
(4) High pO2, low pCO2, less H+, lower temperature

Explanation: Oxyhaemoglobin forms at alveoli where oxygen concentration is high (high pO2), carbon dioxide concentration is low (low pCO2), hydrogen ion concentration is low (less acidic), and temperature is slightly lower. These conditions favor oxygen binding to hemoglobin. Answer: High pO2, low pCO2, less H+, lower temperature.

1. Single Correct Answer MCQ: The partial pressure of oxygen at alveoli favors oxyhaemoglobin formation when it is:
Options:
A. Low
B. High
C. Zero
D. Moderate

Explanation: High pO2 at alveoli ensures hemoglobin binds oxygen efficiently to form oxyhaemoglobin. Low or zero pO2 would prevent oxygen loading. Answer: High.

2. Single Correct Answer MCQ: Low pCO2 at alveoli promotes:
Options:
A. Oxygen unloading
B. Oxyhaemoglobin formation
C. Acidic conditions
D. CO2 retention

Explanation: Low pCO2 reduces H+ concentration and acidity, enhancing hemoglobin's affinity for oxygen. This favors formation of oxyhaemoglobin in the lungs. Answer: Oxyhaemoglobin formation.

3. Single Correct Answer MCQ: Hemoglobin binds oxygen efficiently under which pH condition?
Options:
A. High H+ concentration
B. Low H+ concentration
C. Neutral pH only
D. Any pH

Explanation: Low H+ concentration (less acidic, higher pH) in alveoli enhances oxygen binding to hemoglobin. High H+ or acidic conditions decrease affinity. Answer: Low H+ concentration.

4. Single Correct Answer MCQ: Temperature effect on oxyhaemoglobin formation at lungs:
Options:
A. Higher temperature favors binding
B. Lower temperature favors binding
C. Temperature has no effect
D. Only body temperature is effective

Explanation: Lower temperature at alveoli favors oxygen binding to hemoglobin, increasing oxyhaemoglobin formation. High temperature decreases affinity. Answer: Lower temperature.

5. Single Correct Answer MCQ: The phenomenon where increased CO2 promotes oxygen release is called:
Options:
A. Bohr effect
B. Haldane effect
C. Fick’s law
D. Henry’s law

Explanation: The Bohr effect describes how high CO2 or H+ reduces hemoglobin affinity for oxygen, promoting release in tissues. At alveoli, low CO2 supports oxygen loading. Answer: Bohr effect.

6. Single Correct Answer MCQ: Oxygen loading in alveoli occurs mainly because of:
Options:
A. Low pO2
B. High pO2
C. High CO2
D. High H+

Explanation: High pO2 at alveoli drives diffusion of oxygen into blood and binding to hemoglobin to form oxyhaemoglobin. Answer: High pO2.

7. Assertion-Reason MCQ:
Assertion (A): Oxyhaemoglobin formation occurs efficiently in lungs.
Reason (R): High pO2, low pCO2, low H+, and lower temperature favor hemoglobin binding oxygen.
Options:
A. Both A and R true, R correct explanation
B. Both A and R true, R not correct explanation
C. A true, R false
D. A false, R true

Explanation: Oxyhaemoglobin forms efficiently in lungs under favorable conditions: high oxygen, low CO2, low H+ concentration, and slightly lower temperature. Reason correctly explains assertion. Answer: Both A and R true, R correct explanation.

8. Matching Type MCQ:
Column I: 1. High pO2 2. Low pCO2 3. Low H+ 4. Low temperature
Column II: A. Promotes oxyhaemoglobin formation B. Causes oxygen release C. Unrelated D. Inhibits binding
Options:
A. 1-A, 2-A, 3-A, 4-A
B. 1-B, 2-B, 3-B, 4-B
C. 1-A, 2-B, 3-A, 4-D
D. 1-B, 2-A, 3-D, 4-C

Explanation: All four factors (high pO2, low pCO2, low H+, low temperature) at alveoli favor oxyhaemoglobin formation. Answer: 1-A, 2-A, 3-A, 4-A.

9. Fill in the Blank MCQ: Oxyhaemoglobin formation is maximal when oxygen partial pressure is ______.
Options:
A. High
B. Low
C. Zero
D. Moderate

Explanation: High oxygen partial pressure at alveoli ensures maximum hemoglobin saturation to form oxyhaemoglobin. Answer: High.

10. Choose the correct statements MCQ:
(a) High pO2 favors oxyhaemoglobin formation.
(b) High pCO2 favors oxygen loading in lungs.
(c) Low H+ concentration promotes binding of oxygen.
(d) Lower temperature increases hemoglobin affinity for oxygen.
Options:
1. (a), (c), (d) only
2. (b) and (c) only
3. (a) and (b) only
4. All of the above

Explanation: Favorable conditions at alveoli include high p

Subtopic: Gas Exchange and Partial Pressures

• Partial Pressure: The pressure exerted by a single gas in a mixture of gases, measured in mm Hg.

• pO2: Partial pressure of oxygen in blood or alveoli, indicating oxygen availability for diffusion.

• pCO2: Partial pressure of carbon dioxide, reflecting CO2 levels for exhalation.

• Alveoli: Tiny air sacs in lungs where gas exchange occurs between air and blood.

• Gas Exchange: Diffusion of O2 into blood and CO2 out of blood at alveoli.

• Diffusion Gradient: Difference in partial pressures driving gas movement across respiratory membrane.

• Arterial Blood: Oxygen-rich blood leaving alveoli, with pO2 around 95 mm Hg and pCO2 around 40 mm Hg.

• Atmospheric Air: Contains pO2 ~159 mm Hg and pCO2 ~0.3 mm Hg at sea level.

• Respiratory Membrane: Thin barrier between alveolar air and blood facilitating diffusion.

• Oxygen Transport: Mainly via hemoglobin in red blood cells.

• Carbon Dioxide Transport: Dissolved, as bicarbonate, and bound to hemoglobin for removal.

Lead Question - 2021

The partial pressures (in mm Hg) of oxygen (O2) and carbon dioxide (CO2) at alveoli (the site of diffusion) are:

1. pO2 = 40 and pCO2 = 45
2. pO2 = 95 and pCO2 = 40
3. pO2 = 159 and pCO2 = 0.3
4. pO2 = 104 and pCO2 = 40

Explanation: At alveoli, the partial pressure of oxygen (pO2) is approximately 95 mm Hg, allowing diffusion into blood, while carbon dioxide (pCO2) is around 40 mm Hg, facilitating removal. This reflects the diffusion gradient between alveolar air and pulmonary capillaries. Answer: pO2 = 95 and pCO2 = 40.

1. The main site of gas exchange in lungs is:
Options:
A. Bronchi
B. Alveoli
C. Trachea
D. Pleura

Explanation: Alveoli are tiny air sacs with thin respiratory membranes that allow oxygen to diffuse into blood and carbon dioxide to exit. Bronchi and trachea conduct air, while pleura is a protective membrane. Answer: Alveoli.

2. Arterial blood leaving alveoli has pO2 approximately:
Options:
A. 40 mm Hg
B. 95 mm Hg
C. 159 mm Hg
D. 104 mm Hg

Explanation: Arterial blood leaving alveoli is oxygenated with pO2 around 95 mm Hg, slightly lower than atmospheric oxygen (159 mm Hg) due to humidification and mixing with residual alveolar air. Answer: 95 mm Hg.

3. Carbon dioxide partial pressure in alveoli is approximately:
Options:
A. 0.3 mm Hg
B. 40 mm Hg
C. 45 mm Hg
D. 95 mm Hg

Explanation: The alveolar pCO2 is about 40 mm Hg, facilitating diffusion from blood to alveoli for exhalation. Atmospheric CO2 is negligible (~0.3 mm Hg). Answer: 40 mm Hg.

4. The diffusion of gases depends on:
Options:
A. Partial pressure gradient
B. Blood viscosity
C. Muscle activity
D. Atmospheric pressure only

Explanation: Gas exchange at alveoli follows partial pressure gradients: O2 moves from alveoli (95 mm Hg) to blood (40 mm Hg), and CO2 moves opposite. Blood viscosity or muscles do not directly drive diffusion. Answer: Partial pressure gradient.

5. The pO2 of atmospheric air at sea level is approximately:
Options:
A. 40 mm Hg
B. 95 mm Hg
C. 104 mm Hg
D. 159 mm Hg

Explanation: Atmospheric air contains pO2 ~159 mm Hg at sea level. Humidification and mixing with residual air in alveoli reduce alveolar pO2 to ~95 mm Hg. Answer: 159 mm Hg.

6. Single correct answer: Alveolar pCO2 is maintained around 40 mm Hg by:
Options:
A. Exhalation of CO2
B. O2 diffusion
C. Residual volume
D. Atmospheric CO2

Explanation: Exhalation of CO2 maintains alveolar pCO2 at ~40 mm Hg, ensuring proper diffusion from blood. Residual volume and atmospheric CO2 minimally affect alveolar CO2. Answer: Exhalation of CO2.

7. Assertion-Reason:
Assertion (A): Alveolar pO2 is lower than atmospheric pO2.
Reason (R): Mixing with residual alveolar air and humidification reduce oxygen concentration.
Options:
A. Both A and R true, R correct explanation
B. Both A and R true, R not correct explanation
C. A true, R false
D. A false, R true

Explanation: Alveolar pO2 (~95 mm Hg) is lower than atmospheric pO2 (~159 mm Hg) because inhaled air mixes with residual air and is humidified, reducing oxygen concentration. Answer: Both A and R true, R correct explanation.

8. Matching Type:
Column I: 1. Alveolar pO2 2. Alveolar pCO2 3. Atmospheric pO2
Column II: A. 95 mm Hg B. 40 mm Hg C. 159 mm Hg
Options:
A. 1-A, 2-B, 3-C
B. 1-B, 2-A, 3-C
C. 1-C, 2-A, 3-B
D. 1-A, 2-C, 3-B

Explanation: Correct matching: Alveolar pO2 – 95 mm Hg, Alveolar pCO2 – 40 mm Hg, Atmospheric pO2 – 159 mm Hg. This reflects normal gas exchange physiology. Answer: 1-A, 2-B, 3-C.

9. Fill in the blank: Oxygen diffuses from alveoli into blood due to _______.
Options:
A. Partial pressure gradient
B. Blood flow rate
C. Hemoglobin concentration
D. Tidal volume

Explanation: Oxygen moves from alveoli (pO2 95 mm Hg) to blood (pO2 40 mm Hg) following the partial pressure gradient, ensuring efficient oxygenation. Other factors assist transport but do not drive diffusion. Answer: Partial pressure gradient.

10. Choose the correct statements:
1. Alveolar pO2 is 95 mm Hg
2. Alveolar pCO2 is 40 mm Hg
3. Atmospheric pO2 is 104 mm Hg
4. Diffusion depends on partial pressure gradients
Options:
A. 1, 2, 4 only
B. 1, 3, 4 only
C. 2, 3 only
D. 1, 2, 3, 4

Explanation: Statements 1, 2, and 4 are correct. Alveolar pO2 is ~95 mm Hg, pCO2 ~40 mm Hg, and diffusion occurs along partial pressure gradients. Atmospheric pO2 is ~159 mm Hg, not 104. Answer: 1, 2, 4 only.

Subtopic: Respiratory Regulation and Gas Transport

Keyword Definitions:
Pneumotaxic Centre: Region in the pons that regulates the rate and pattern of breathing.
Dissociation Curve: Graph showing the relationship between oxygen partial pressure and hemoglobin saturation.
Carbonic Anhydrase: Enzyme in red blood cells catalyzing conversion of CO2 and water to carbonic acid.
Primary site of gas exchange: Alveoli, where oxygen enters blood and carbon dioxide is removed.
R.B.C.: Red Blood Cells, which transport oxygen and carbon dioxide.
Haemoglobin: Oxygen-carrying protein in RBCs.
Pons: Part of brainstem controlling respiration.
Alveoli: Small air sacs in lungs facilitating gas exchange.

Lead Question - 2020 (COVID Reexam):
Match the following columns and select the correct option:
Column - I Column - II
(a) Pneumotaxic Centre (i) Alveoli
(b) Dissociation curve (ii) Pons region of the brain
(c) Carbonic Anhydrase (iii) Haemoglobin
(d) Primary site of exchange (iv) R.B.C.
1. (a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)
2. (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)
3. (a)-(iii), (b)-(ii), (c)-(iv), (d)-(i)
4. (a)-(iv), (b)-(i), (c)-(iii), (d)-(ii)
Explanation: The pneumotaxic centre regulates breathing and is located in the pons (a-ii). Dissociation curve represents oxygen binding with haemoglobin (b-iii). Carbonic anhydrase is present in RBCs (c-iv). The primary site of gas exchange is the alveoli (d-i). Correct answer is 2.

1. Single Correct Answer MCQ:
Which region of the brain regulates breathing rate?
1. Medulla oblongata
2. Pons
3. Cerebellum
4. Hypothalamus
Explanation: The pons contains the pneumotaxic centre which regulates the rate and pattern of breathing. Medulla also contributes but pons specifically modulates inspiratory and expiratory duration. Cerebellum and hypothalamus do not directly control respiration. Correct answer is 2. Pons.

2. Single Correct Answer MCQ:
Carbonic anhydrase is present in:
1. Alveoli
2. RBCs
3. Plasma
4. Bronchioles
Explanation: Carbonic anhydrase is present inside red blood cells and catalyzes the reversible conversion of CO2 and water to carbonic acid, facilitating CO2 transport and pH regulation. It is not present in alveoli, plasma, or bronchioles. Correct answer is 2. RBCs.

3. Single Correct Answer MCQ:
The oxygen dissociation curve represents:
1. CO2 solubility
2. Oxygen saturation of haemoglobin
3. Respiratory rate
4. Tidal volume
Explanation: Dissociation curve illustrates the relationship between oxygen partial pressure and the saturation of haemoglobin, showing how easily hemoglobin acquires and releases oxygen. It does not represent CO2 solubility, respiratory rate, or tidal volume. Correct answer is 2. Oxygen saturation of haemoglobin.

4. Single Correct Answer MCQ:
Primary site for gas exchange in lungs is:
1. Bronchi
2. Alveoli
3. Trachea
4. Bronchioles
Explanation: Alveoli are tiny sacs where oxygen enters the blood and carbon dioxide is removed, forming the primary site for gas exchange. Bronchi, trachea, and bronchioles serve as air passages. Correct answer is 2. Alveoli.

5. Single Correct Answer MCQ:
Haemoglobin is found in:
1. Plasma
2. RBCs
3. White blood cells
4. Platelets
Explanation: Haemoglobin is an oxygen-carrying protein located inside red blood cells. It binds oxygen in lungs and releases it in tissues. Plasma, white blood cells, and platelets do not contain haemoglobin. Correct answer is 2. RBCs.

6. Single Correct Answer MCQ:
Which enzyme helps in CO2 transport in blood?
1. Pepsin
2. Carbonic anhydrase
3. Amylase
4. Lipase
Explanation: Carbonic anhydrase in red blood cells catalyzes CO2 and water conversion to carbonic acid, facilitating CO2 transport in blood. Pepsin digests proteins, amylase digests starch, and lipase digests fats. Correct answer is 2. Carbonic anhydrase.

7. Assertion-Reason MCQ:
Assertion (A): Alveoli are the primary sites of gas exchange.
Reason (R): They provide large surface area and thin walls for diffusion.
1. Both A and R are true, R is correct explanation of A
2. Both A and R are true, R is not correct explanation of A
3. A is true, R is false
4. A is false, R is true
Explanation: Alveoli are the main site for gas exchange, with large surface area and thin walls facilitating oxygen and carbon dioxide diffusion. Both statements are correct, and the reason explains the assertion. Correct answer is 1. Both A and R are true, R is correct explanation.

8. Matching Type MCQ:
Match the item with its description:
A. Pneumotaxic Centre B. Dissociation Curve C. Carbonic Anhydrase D. Primary Gas Exchange
1. RBC enzyme
2. Brain pons region
3. Oxygen-haemoglobin relation
4. Alveoli
Options:
1. A-2, B-3, C-1, D-4
2. A-3, B-2, C-4, D-1
3. A-1, B-4, C-2, D-3
4. A-4, B-1, C-3, D-2
Explanation: Pneumotaxic centre is in the pons (A-2), dissociation curve shows oxygen-haemoglobin relation (B-3), carbonic anhydrase is RBC enzyme (C-1), and alveoli are primary gas exchange site (D-4). Correct answer is 1. A-2, B-3, C-1, D-4.

9. Fill in the Blanks MCQ:
The enzyme _______ catalyzes conversion of CO2 to carbonic acid in RBCs.
1. Pepsin
2. Carbonic Anhydrase
3. Lipase
4. Amylase
Explanation: Carbonic anhydrase in red blood cells catalyzes the reversible reaction of CO2 and water to carbonic acid, facilitating CO2 transport and acid-base balance. Pepsin digests proteins, lipase digests fats, and amylase digests starch. Correct answer is 2. Carbonic Anhydrase.

10. Choose the correct statements MCQ:
Select correct statements:
1. Dissociation curve shows oxygen-hemoglobin relationship
2. Alveoli are primary gas exchange sites
3. Pneumotaxic centre is in medulla
4. Carbonic anhydrase is in RBCs
Options:
1. 1, 2, 4
2. 1 and 3
3. 2 and 3
4. 3 and 4
Explanation: The oxygen dissociation curve shows hemoglobin saturation (1), alveoli are primary gas exchange sites (2), and carbonic anhydrase is in RBCs (4). Pneumotaxic centre is in pons, not medulla. Correct statements are 1, 2, 4. Correct answer is 1. 1, 2, 4.

Subtopic: Lung Volumes and Capacities

Keyword Definitions:
Total Lung Capacity (TLC): Maximum volume of air in lungs after forced inspiration, sum of all lung volumes.
Residual Volume (RV): Air remaining in lungs after maximal exhalation.
Expiratory Reserve Volume (ERV): Extra air exhaled after normal expiration.
Tidal Volume (TV): Volume of air inhaled or exhaled during normal breathing.
Inspiratory Capacity (IC): Maximum air that can be inhaled after normal exhalation.
Vital Capacity (VC): Maximum air exhaled after maximal inhalation.
Functional Residual Capacity (FRC): Air remaining in lungs after normal exhalation.
Expiratory Capacity (EC): Volume exhaled after normal inspiration (less commonly used).

Lead Question - 2020 (COVID Reexam):
The Total Lung Capacity (TLC) is the total volume of air accommodated in the lungs at the end of forced inspiration. This includes:
1. RV; IC (Inspiratory Capacity); EC (Expiratory Capacity); and ERV
2. RV; ERV; IC and EC
3. RV; ERV; VC (Vital Capacity) and FRC (Functional Residual Capacity)
4. RV (Residual Volume); ERV (Expiratory Reserve Volume); TV (Tidal Volume)
Explanation: Total Lung Capacity (TLC) includes all lung volumes: residual volume (RV), expiratory reserve volume (ERV), tidal volume (TV), and inspiratory capacity (IC). Vital capacity (VC) is the sum of TV, IRV, and ERV. Correct combination representing TLC is 4. RV; ERV; TV; IC completes TLC. Correct answer is 4.

1. Single Correct Answer MCQ:
Which volume represents air remaining after maximal exhalation?
1. Tidal Volume
2. Residual Volume
3. Expiratory Reserve Volume
4. Inspiratory Capacity
Explanation: Residual Volume (RV) is the air remaining in lungs after maximal exhalation, preventing lung collapse and allowing continuous gas exchange. Tidal volume is normal breathing, ERV is extra exhalation, and IC is maximal inhalation. Correct answer is 2. Residual Volume.

2. Single Correct Answer MCQ:
Which volume is exhaled beyond normal expiration?
1. Tidal Volume
2. Residual Volume
3. Expiratory Reserve Volume
4. Inspiratory Reserve Volume
Explanation: Expiratory Reserve Volume (ERV) is the additional air exhaled after normal expiration. Tidal volume is normal breath, residual volume remains after maximal exhalation, and inspiratory reserve volume is extra inhalation. Correct answer is 3. Expiratory Reserve Volume.

3. Single Correct Answer MCQ:
Tidal Volume represents:
1. Maximum air inhaled
2. Normal breath air volume
3. Air remaining in lungs
4. Extra air exhaled
Explanation: Tidal Volume (TV) is the amount of air inhaled or exhaled during normal breathing. Maximum air inhaled is IC, air remaining is RV, extra air exhaled is ERV. Correct answer is 2. Normal breath air volume.

4. Single Correct Answer MCQ:
Vital Capacity (VC) includes which volumes?
1. TV + IRV + ERV
2. TV + RV
3. RV + FRC
4. IC + RV
Explanation: Vital Capacity (VC) is the maximum air exhaled after maximal inhalation, consisting of tidal volume (TV), inspiratory reserve volume (IRV), and expiratory reserve volume (ERV). RV remains in lungs and is not part of VC. Correct answer is 1. TV + IRV + ERV.

5. Single Correct Answer MCQ:
Functional Residual Capacity (FRC) is:
1. TV + IRV
2. RV + ERV
3. IC + TV
4. TV + ERV
Explanation: Functional Residual Capacity (FRC) is the air left in lungs after normal exhalation, which includes residual volume (RV) plus expiratory reserve volume (ERV). TV is normal breathing, IC is maximal inhalation. Correct answer is 2. RV + ERV.

6. Single Correct Answer MCQ:
Which lung capacity measures maximum air inhaled after normal exhalation?
1. Tidal Volume
2. Inspiratory Capacity
3. Expiratory Reserve Volume
4. Vital Capacity
Explanation: Inspiratory Capacity (IC) is the maximum volume of air inhaled after a normal exhalation. Tidal volume is normal breath, ERV is extra exhaled air, and VC is maximal exhalation after maximal inhalation. Correct answer is 2. Inspiratory Capacity.

7. Assertion-Reason MCQ:
Assertion (A): TLC is the sum of all lung volumes.
Reason (R): It includes TV, IRV, ERV, and RV.
1. Both A and R are true, R is correct explanation of A
2. Both A and R are true, R is not correct explanation of A
3. A is true, R is false
4. A is false, R is true
Explanation: Total Lung Capacity (TLC) represents the sum of all lung volumes, including tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume. The reason correctly explains the assertion. Correct answer is 1. Both A and R are true, R is correct explanation.

8. Matching Type MCQ:
Match the lung volume with its description:
A. RV B. TV C. ERV D. IC
1. Normal breath air
2. Extra air inhaled
3. Extra air exhaled
4. Air remaining after maximal exhalation
Options:
1. A-4, B-1, C-3, D-2
2. A-1, B-2, C-3, D-4
3. A-3, B-1, C-2, D-4
4. A-2, B-3, C-1, D-4
Explanation: Residual Volume (RV) remains after maximal exhalation (A-4), Tidal Volume (TV) is normal breath (B-1), Expiratory Reserve Volume (ERV) is extra air exhaled (C-3), and Inspiratory Capacity (IC) is extra air inhaled (D-2). Correct answer is 1. A-4, B-1, C-3, D-2.

9. Fill in the Blanks MCQ:
Total Lung Capacity (TLC) = RV + TV + ERV + _______.
1. IC
2. FRC
3. VC
4. EC
Explanation: Total Lung Capacity is the sum of all lung volumes, including residual volume, tidal volume, expiratory reserve volume, and inspiratory capacity. FRC and VC are parts of TLC but IC completes the calculation. Correct answer is 1. IC.

10. Choose the correct statements MCQ:
Select correct statements about TLC:
1. Sum of all lung volumes
2. Includes RV, TV, ERV, IC
3. Only measures air exhaled
4. Does not include residual volume
Options:
1. 1 and 2
2. 2 and 3
3. 3 and 4
4. 1 and 4
Explanation: Total Lung Capacity is the sum of all lung volumes and includes residual volume, tidal volume, expiratory reserve volume, and inspiratory capacity. It measures total air in lungs, not just exhaled air. Correct statements are 1 and 2. Correct answer is 1. 1 and 2.

Subtopic: Mechanics of Breathing

Keyword Definitions:

• Inspiration – Process of drawing air into the lungs during breathing.

• Diaphragm – Dome-shaped muscle separating thoracic and abdominal cavities, contracts to facilitate inhalation.

• External intercostal muscles – Muscles between ribs, contract to elevate rib cage and expand thoracic volume.

• Pulmonary volume – Total volume of air in the lungs, varies during breathing cycles.

• Intra-pulmonary pressure – Pressure inside the lungs relative to atmospheric pressure, decreases during inspiration.

• Expiration – Process of expelling air from lungs.

• Thoracic cavity – Chamber enclosed by ribs and diaphragm housing lungs and heart.

• Alveoli – Microscopic air sacs in lungs where gas exchange occurs.

• Respiratory muscles – Muscles facilitating inhalation and exhalation, including diaphragm and intercostals.

• Atmospheric pressure – Pressure exerted by surrounding air outside the body.

• Boyle’s Law – Principle explaining inverse relationship between volume and pressure in lungs during breathing.

Lead Question - 2020

Select the correct events that occur during inspiration:
(a) Contraction of diaphragm
(b) Contraction of external inter-costal muscles
(c) Pulmonary volume decreases
(d) Intra pulmonary pressure increases
(1) (a), (b) and (d)
(2) only (d)
(3) (a) and (b)
(4) (c) and (d)

Explanation: During inspiration, the diaphragm and external intercostal muscles contract, enlarging thoracic cavity volume. This increases pulmonary volume and decreases intra-pulmonary pressure, allowing air to flow into lungs. Therefore, the correct events are contraction of diaphragm and external intercostals. Correct answer is (3) (a) and (b).

1. Single Correct Answer: What happens to intra-pulmonary pressure during inspiration?
(1) Increases
(2) Decreases
(3) Remains same
(4) Becomes equal to atmospheric pressure

Explanation: Intra-pulmonary pressure decreases below atmospheric pressure during inspiration, allowing air to enter the lungs due to the pressure gradient. Correct answer is (2) Decreases.

2. Single Correct Answer: Which muscle is primarily responsible for inhalation?
(1) Diaphragm
(2) Rectus abdominis
(3) Internal intercostals
(4) Sternocleidomastoid

Explanation: The diaphragm contracts during inspiration, moving downward to expand thoracic cavity and facilitate airflow into the lungs. Correct answer is (1) Diaphragm.

3. Single Correct Answer: Contraction of external intercostal muscles leads to:
(1) Rib cage depression
(2) Rib cage elevation
(3) Thoracic cavity reduction
(4) Lung collapse

Explanation: External intercostal muscles contract to elevate the ribs, expanding thoracic volume and aiding inspiration. Correct answer is (2) Rib cage elevation.

4. Single Correct Answer: Pulmonary volume during inspiration:
(1) Increases
(2) Decreases
(3) Remains constant
(4) Becomes zero

Explanation: Pulmonary volume increases as thoracic cavity enlarges during inspiration, decreasing intra-pulmonary pressure and allowing air inflow. Correct answer is (1) Increases.

5. Assertion-Reason:
Assertion (A): Inspiration occurs when intra-pulmonary pressure falls below atmospheric pressure.
Reason (R): Contraction of diaphragm and external intercostals increases thoracic cavity volume.
(1) Both A and R true, R explains A
(2) Both A and R true, R does not explain A
(3) A true, R false
(4) A false, R true

Explanation: Inspiration results from decreased intra-pulmonary pressure below atmospheric pressure, caused by diaphragm and external intercostal contraction increasing thoracic volume. Both assertion and reason are true, and reason correctly explains assertion. Correct answer is (1).

6. Single Correct Answer: Which process occurs actively during quiet breathing?
(1) Expiration
(2) Inspiration
(3) Gas exchange at alveoli
(4) Diffusion only

Explanation: Inspiration during quiet breathing is an active process involving muscle contraction, whereas expiration is mostly passive. Correct answer is (2) Inspiration.

7. Matching Type: Match structure with function during inspiration:
(a) Diaphragm – i. Expands thoracic cavity
(b) External intercostals – ii. Elevates ribs
(c) Internal intercostals – iii. Forced expiration
(d) Lungs – iv. Receive air
Options:
(1) a-i, b-ii, c-iii, d-iv
(2) a-ii, b-i, c-iv, d-iii
(3) a-i, b-iii, c-ii, d-iv
(4) a-iv, b-ii, c-i, d-iii

Explanation: Diaphragm expands thoracic cavity (a-i), external intercostals elevate ribs (b-ii), internal intercostals act in forced expiration (c-iii), and lungs receive air (d-iv). Correct answer is (1).

8. Fill in the blank: During inspiration, _______ moves downward to increase thoracic cavity volume.
(1) Diaphragm
(2) Heart
(3) Stomach
(4) Liver

Explanation: The diaphragm contracts and moves downward during inspiration, enlarging thoracic cavity and reducing intra-pulmonary pressure. Correct answer is (1) Diaphragm.

9. Single Correct Answer: Which statement is true about quiet inspiration?
(1) Passive process
(2) Diaphragm relaxes
(3) Thoracic volume increases
(4) Intra-pulmonary pressure rises

Explanation: Quiet inspiration is active, involving diaphragm contraction, elevating thoracic volume and lowering intra-pulmonary pressure. Correct answer is (3) Thoracic volume increases.

10. Choose the correct statements:
(a) Diaphragm contracts during inspiration
(b) External intercostals contract during inspiration
(c) Pulmonary volume decreases during inspiration
(d) Intra-pulmonary pressure falls during inspiration
Options:
(1) a, b, d
(2) a, c, d
(3) b, c, d
(4) a, b, c

Explanation: During inspiration, diaphragm and external intercostals contract, increasing pulmonary volume and lowering intra-pulmonary pressure. Pulmonary volume does not decrease. Correct answer is (1) a, b, d.

Topic: Transport of Gases
Subtopic: Oxygen Transport in Blood

• Oxyhaemoglobin: Complex of oxygen bound to haemoglobin in red blood cells for transport from lungs to tissues.

• Partial Pressure of Oxygen (pO2): Measure of oxygen concentration in blood or alveoli influencing haemoglobin binding.

• Partial Pressure of Carbon Dioxide (pCO2): Measure of CO2 concentration in blood or alveoli affecting oxygen transport and affinity.

• Bohr Effect: Influence of pH and CO2 concentration on haemoglobin's oxygen binding capacity.

• Haemoglobin: Protein in red blood cells that binds oxygen and facilitates transport.

• Alveoli: Air sacs in lungs where gas exchange occurs.

• Acid-Base Balance: Regulation of blood pH affecting oxygen delivery.

• Oxygen Saturation: Percentage of haemoglobin bound with oxygen in blood.

• Carbonic Anhydrase: Enzyme that catalyzes conversion of CO2 to bicarbonate in red blood cells.

• Oxygen-Haemoglobin Dissociation Curve: Graph showing relation between pO2 and haemoglobin saturation.

• Affinity: Tendency of haemoglobin to bind oxygen, influenced by pH, CO2, and temperature.

Lead Question (2020): Identify the wrong statement with reference to transport of oxygen:
Options:
1. Higher H+ conc. in alveoli favours the formation of oxyhaemoglobin
2. Low pCO2 in alveoli favours the formation of oxyhaemoglobin
3. Binding of oxygen with haemoglobin is mainly related to partial pressure of O2
4. Partial pressure of CO2 can interfere with O2 binding with haemoglobin

Explanation: Correct answer is 1. Higher H+ concentration decreases haemoglobin’s affinity for oxygen (Bohr effect), reducing oxyhaemoglobin formation. Low pCO2 favours oxygen binding, binding primarily depends on pO2, and elevated CO2 can interfere with oxygen transport by shifting the dissociation curve.

1. Single Correct Answer MCQ:
What does the Bohr effect describe?
Options:
a. Effect of CO2 and H+ on oxygen binding
b. Effect of temperature on respiration
c. Effect of hemoglobin mutations
d. Effect of oxygen on CO2 binding

Explanation: Correct answer is a. The Bohr effect describes decreased oxygen affinity of haemoglobin due to increased H+ and CO2, facilitating oxygen release in tissues. This physiological adaptation optimizes oxygen transport according to tissue metabolic demands.

2. Single Correct Answer MCQ:
Which factor primarily determines oxygen binding to haemoglobin?
Options:
a. pO2
b. pCO2
c. Blood glucose
d. Body temperature

Explanation: Correct answer is a. Oxygen binding to haemoglobin depends mainly on pO2. Higher pO2 in alveoli promotes oxygen loading, while lower pO2 in tissues facilitates release. Other factors like pH and CO2 influence but do not primarily determine oxygen binding.

3. Single Correct Answer MCQ:
Which gas interferes with oxygen binding to haemoglobin?
Options:
a. CO2
b. N2
c. O2
d. H2

Explanation: Correct answer is a. Carbon dioxide interferes with oxygen binding by lowering blood pH and promoting release of oxygen (Bohr effect). N2, O2, and H2 do not directly affect haemoglobin’s oxygen affinity in physiological conditions.

4. Single Correct Answer MCQ:
Low pCO2 in alveoli causes:
Options:
a. Formation of oxyhaemoglobin
b. Release of oxygen
c. Increased acidity
d. Decreased pO2

Explanation: Correct answer is a. Low alveolar pCO2 reduces H+ concentration, increasing haemoglobin’s affinity for oxygen and promoting oxyhaemoglobin formation. This ensures efficient oxygen loading in lungs while CO2 transport occurs simultaneously.

5. Single Correct Answer MCQ:
Where does maximum oxyhaemoglobin formation occur?
Options:
a. Lungs alveoli
b. Tissues
c. Capillaries
d. Veins

Explanation: Correct answer is a. Maximum oxyhaemoglobin formation occurs in alveoli of lungs where pO2 is high and pCO2 is low, facilitating efficient oxygen uptake. Tissue capillaries with lower pO2 promote oxygen release.

6. Single Correct Answer MCQ:
Which factor shifts the oxygen-haemoglobin dissociation curve to the right?
Options:
a. Increased CO2 and H+
b. Low temperature
c. Decreased CO2
d. High pO2

Explanation: Correct answer is a. Increased CO2 and H+ reduce haemoglobin’s oxygen affinity, shifting the curve right, promoting oxygen release to tissues. Low temperature or low CO2 shifts the curve left, enhancing oxygen binding.

7. Assertion-Reason MCQ:
Assertion (A): Oxygen transport depends on both pO2 and pCO2.
Reason (R): pCO2 and H+ affect haemoglobin’s affinity for oxygen.
Options:
a. Both A and R are true, R explains A
b. Both A and R are true, R does not explain A
c. A is true, R is false
d. A is false, R is true

Explanation: Correct answer is a. Oxygen transport is influenced by pO2 for loading and pCO2/H+ for unloading (Bohr effect). The reason explains the assertion since CO2 and H+ modify haemoglobin affinity, ensuring tissue oxygen delivery matches metabolic demand.

8. Matching Type MCQ:
Match the site with oxygen transport characteristic:
(a) Lungs | (i) Oxygen unloading
(b) Tissues | (ii) High pO2, low pCO2
(c) Arterioles | (iii) Oxygen delivery
(d) Capillaries | (iv) Moderate pO2, high pCO2
Options:
1. a-ii, b-i, c-iii, d-iv
2. a-i, b-ii, c-iii, d-iv
3. a-iii, b-iv, c-ii, d-i
4. a-iv, b-iii, c-i, d-ii

Explanation: Correct answer is 1. Lungs have high pO2 and low pCO2 (a-ii) favoring oxygen loading. Tissues promote oxygen unloading (b-i). Arterioles deliver oxygen (c-iii) and capillaries have moderate pO2 and high CO2 (d-iv), optimizing gas exchange.

9. Fill in the Blanks MCQ:
The decrease in haemoglobin’s oxygen affinity due to high H+ is called ________.
Options:
a. Bohr effect
b. Haldane effect
c. Fick’s law
d. Dalton’s law

Explanation: Correct answer is a. The Bohr effect describes decreased haemoglobin affinity for oxygen in response to increased H+ concentration, facilitating oxygen release in metabolically active tissues while maintaining efficient transport in lungs.

Subtopic: Lung Volumes and Capacities

• Tidal Volume (TV): The volume of air inhaled or exhaled in a normal breath, typically 400–500 mL.

• Expiratory Reserve Volume (ERV): The additional volume of air that can be exhaled after normal expiration.

• Residual Volume (RV): The volume of air remaining in lungs after maximal exhalation, cannot be voluntarily expelled.

• Expiratory Capacity (EC): The total air that can be exhaled after a normal inspiration; EC = TV + ERV.

• Lung Volumes: Different measurable amounts of air in lungs at various stages of respiration.

• Lung Capacities: Combination of two or more lung volumes representing functional aspects of respiratory system.

• Athlete: A person with high physical fitness and often increased lung capacities.

• Respiratory Mechanics: Study of ventilation, lung volumes, and airflow dynamics.

• Maximal Expiration: Complete exhalation following a deep inhalation.

• Ventilation: Movement of air into and out of the lungs.

• Pulmonary Function: Functional assessment of lung volumes, capacities, and gas exchange efficiency.

Lead Question (2019): Tidal Volume and Expiratory Reserve Volume of an athlete is 500 mL and 1000 mL respectively. What will be his Expiratory Capacity if the Residual Volume is 1200 mL?

Options:
1. 1500 mL
2. 1700 mL
3. 2200 mL
4. 2700 mL

Explanation: Correct answer is 1. Expiratory Capacity (EC) is the sum of Tidal Volume and Expiratory Reserve Volume. Here, EC = TV + ERV = 500 mL + 1000 mL = 1500 mL. Residual volume is not included in EC calculation. This reflects the maximum volume of air exhaled after a normal inspiration.

1. Single Correct Answer MCQ:
The total lung capacity (TLC) is the sum of:
Options:
a. TV + ERV
b. TV + ERV + RV + Inspiratory Reserve Volume
c. TV + RV
d. ERV + RV

Explanation: Correct answer is b. Total lung capacity includes Tidal Volume, Expiratory Reserve Volume, Residual Volume, and Inspiratory Reserve Volume. It represents the maximum volume of air the lungs can hold, providing a measure of pulmonary function and respiratory efficiency.

2. Single Correct Answer MCQ:
Functional Residual Capacity (FRC) equals:
Options:
a. TV + ERV
b. ERV + RV
c. TV + IRV
d. TLC - TV

Explanation: Correct answer is b. Functional Residual Capacity is the volume of air remaining in lungs after a normal expiration, calculated as ERV + RV. It represents the baseline air available for gas exchange between breaths.

3. Single Correct Answer MCQ:
An athlete usually has higher than normal:
Options:
a. Residual Volume
b. Lung Compliance
c. Tidal Volume
d. Dead Space

Explanation: Correct answer is c. Athletes often have increased Tidal Volume due to enhanced respiratory efficiency. Residual volume and dead space remain relatively constant, while lung compliance may improve slightly. Higher tidal volume improves oxygen intake during intense physical activity.

4. Single Correct Answer MCQ:
Expiratory Reserve Volume is best described as:
Options:
a. Air exhaled during normal breath
b. Air that can be forcefully exhaled after normal expiration
c. Air remaining after maximal exhalation
d. Total lung air capacity

Explanation: Correct answer is b. ERV is the additional air that can be expelled after normal exhalation, reflecting the reserve capacity of lungs. It is distinct from residual volume, which cannot be exhaled, and tidal volume, which represents normal breathing.

5. Single Correct Answer MCQ:
Which lung volume cannot be voluntarily exhaled?
Options:
a. Tidal Volume
b. Expiratory Reserve Volume
c. Residual Volume
d. Inspiratory Reserve Volume

Explanation: Correct answer is c. Residual Volume is the air remaining in lungs after maximal exhalation. It prevents lung collapse and maintains continuous gas exchange. Other volumes, like TV, ERV, and IRV, can be voluntarily inhaled or exhaled.

6. Single Correct Answer MCQ:
Vital Capacity (VC) is calculated as:
Options:
a. TV + ERV
b. TV + IRV + ERV
c. TLC - RV
d. b and c both

Explanation: Correct answer is d. Vital Capacity, the maximum air exhaled after full inspiration, equals TV + IRV + ERV or TLC - RV. It measures lung performance and functional reserve, critical in assessing respiratory health.

7. Assertion-Reason MCQ:
Assertion (A): Expiratory Capacity increases in athletes.
Reason (R): Tidal Volume and Expiratory Reserve Volume are higher in trained individuals.
Options:
a. Both A and R are true, R explains A
b. Both A and R are true, R does not explain A
c. A is true, R is false
d. A is false, R is true

Explanation: Correct answer is a. Athletes have higher Tidal Volume and Expiratory Reserve Volume, which increases Expiratory Capacity. Both assertion and reason are correct, and reason explains the physiological basis for the higher EC observed in trained individuals.

8. Matching Type MCQ:
Match the lung volumes with their description:
Column-I Column-II
(a) Tidal Volume (i) Air remaining after maximal exhalation
(b) Expiratory Reserve Volume (ii) Normal breath exhaled air
(c) Residual Volume (iii) Maximal air exhaled after normal expiration
(d) Inspiratory Reserve Volume (iv) Maximal air inhaled after normal inspiration
Options:
1. a-ii, b-iii, c-i, d-iv
2. a-i, b-ii, c-iii, d-iv
3. a-iii, b-ii, c-i, d-iv
4. a-iv, b-iii, c-ii, d-i

Explanation: Correct answer is 1. Tidal Volume is normal exhalation, ERV is air forcibly exhaled after normal breath, Residual Volume cannot be exhaled, and IRV is air forcibly inhaled. Correct matching demonstrates understanding of lung volume distinctions.

9. Fill in the Blanks / Completion MCQ:
Expiratory Capacity is equal to ________ + ________.
Options:
a. TV + IRV

Subtopic: Respiratory Disorders

Keyword Definitions:

• Wheezing: High-pitched whistling sound during breathing due to airway obstruction.

• Bronchi: Large air passages that lead from trachea to lungs.

• Bronchioles: Smaller branches of bronchi within the lungs.

• Alveoli: Tiny air sacs in lungs for gas exchange.

• Surfactants: Substances secreted by pneumocytes to reduce surface tension in alveoli.

• Inflammation: Immune response causing swelling and irritation of tissues.

• Allergens: Substances that trigger allergic reactions.

Lead Question (2019):

Due to increasing air-borne allergens and pollutants, many people in urban areas are suffering from respiratory disorder causing wheezing due to:
(1) benign growth on mucous lining of nasal cavity.
(2) inflammation of bronchi and bronchioles
(3) proliferation of fibrous tissues and damage of the alveolar walls.
(4) reduction in the secretion of surfactants by pneumocytes

Explanation: Correct answer is (2). Wheezing occurs due to narrowing and inflammation of bronchi and bronchioles, typical in conditions like asthma or bronchitis. Airway obstruction caused by allergens or pollutants triggers smooth muscle contraction, mucous production, and inflammation, resulting in difficulty breathing and characteristic whistling sounds.

1) Single Correct Answer MCQ:
Which cells produce surfactants in lungs?
(1) Ciliated epithelial cells
(2) Pneumocytes
(3) Goblet cells
(4) Alveolar macrophages

Explanation: Correct answer is (2). Pneumocytes, specifically type II alveolar cells, secrete surfactants that reduce surface tension, preventing alveolar collapse and facilitating gas exchange in the lungs.

2) Single Correct Answer MCQ:
Chronic inflammation of bronchi is known as:
(1) Asthma
(2) Bronchitis
(3) Emphysema
(4) Pneumonia

Explanation: Correct answer is (2). Bronchitis is inflammation of the bronchi, leading to cough, mucus production, and wheezing. Acute or chronic exposure to allergens or pollutants often triggers the condition.

3) Single Correct Answer MCQ:
Wheezing is primarily caused by:
(1) Alveolar collapse
(2) Airway narrowing
(3) Pulmonary edema
(4) Pneumothorax

Explanation: Correct answer is (2). Wheezing results from narrowing of the bronchi and bronchioles due to inflammation, smooth muscle contraction, and mucus accumulation, producing high-pitched sounds during exhalation.

4) Single Correct Answer MCQ:
Which pollutant commonly triggers airway inflammation?
(1) Nitrogen oxides
(2) Carbon monoxide
(3) Ozone
(4) All of the above

Explanation: Correct answer is (4). Nitrogen oxides, carbon monoxide, and ozone are air pollutants that irritate the respiratory tract, causing inflammation, bronchoconstriction, and wheezing in sensitive individuals.

5) Single Correct Answer MCQ:
Allergic asthma is triggered by:
(1) Viral infection
(2) Airborne allergens
(3) Bacterial infection
(4) High blood pressure

Explanation: Correct answer is (2). Airborne allergens such as pollen, dust, and mold can trigger immune-mediated inflammation in bronchi, resulting in asthma symptoms including wheezing and shortness of breath.

6) Single Correct Answer MCQ:
Which structure connects trachea to lungs?
(1) Bronchi
(2) Bronchioles
(3) Alveoli
(4) Larynx

Explanation: Correct answer is (1). The bronchi are major air passages branching from the trachea into each lung, further dividing into bronchioles, and play a key role in conducting air and being susceptible to inflammation.

7) Assertion-Reason MCQ:
Assertion (A): Wheezing occurs due to airway inflammation.
Reason (R): Pollutants and allergens trigger smooth muscle contraction and mucus secretion in bronchi.
Options:
(1) A true, R true, R correct explanation
(2) A true, R true, R not correct explanation
(3) A true, R false
(4) A false, R true

Explanation: Correct answer is (1). Wheezing results from inflamed and narrowed airways. Allergens and pollutants stimulate bronchial smooth muscles to contract and increase mucus production, directly explaining the occurrence of wheezing.

8) Matching Type MCQ:
Match the disorder with primary affected structure:
(a) Asthma - (i) Alveoli
(b) Bronchitis - (ii) Bronchi
(c) Emphysema - (iii) Bronchioles
Options:
(1) a-iii, b-ii, c-i
(2) a-ii, b-i, c-iii
(3) a-i, b-iii, c-ii
(4) a-ii, b-iii, c-i

Explanation: Correct answer is (1). Asthma affects bronchioles, bronchitis affects bronchi, and emphysema involves alveolar wall damage, reducing gas exchange efficiency.

9) Fill in the Blanks MCQ:
_________ cells in alveoli secrete surfactants to prevent collapse.
(1) Type I pneumocytes
(2) Type II pneumocytes
(3) Goblet cells
(4) Ciliated epithelial cells

Explanation: Correct answer is (2). Type II pneumocytes produce surfactants that lower surface tension in alveoli, ensuring structural stability during breathing cycles.

10) Choose the correct statements MCQ:
(1) Bronchioles are smaller branches of bronchi
(2) Wheezing is caused by airway narrowing
(3) Allergens can trigger inflammation of bronchi
(4) Pneumocytes produce surfactants to reduce alveolar collapse

Explanation: Correct answer is (1,2,3,4). All statements are correct. Bronchioles conduct air from bronchi to alveoli, wheezing arises from airway constriction, allergens cause inflammation, and pneumocytes secrete surfactants to maintain alveolar stability.</

Subtopic: Lung Volumes and Capacities

Keyword Definitions:

• Tidal volume (TV): Volume of air inhaled or exhaled in a normal breath, ~500 mL.

• Inspiratory Reserve Volume (IRV): Maximum air inhaled beyond normal inspiration, ~2500–3000 mL.

• Expiratory Reserve Volume (ERV): Maximum air exhaled beyond normal expiration, ~1100–1200 mL.

• Residual Volume (RV): Air remaining in lungs after forceful expiration, ~1000–1100 mL.

• Lung capacity: Sum of various lung volumes.

• Pulmonary ventilation: Total air movement in and out of lungs.

Lead Question - 2018

Match the items given in Column I with those in Column II and select the correct option given below :

Column –I | Column –II

a. Tidal volume | i. 2500 – 3000 mL

b. Inspiratory Reserve volume | ii. 1100 - 1200 mL

c. Expiratory Reserve volume | iii. 500 – 550 mL

d. Residual volume | iv. 1000 – 1100 mL

(A) a – iv, b – iii, c – ii, d – i

(B) a – iii, b – ii, c – i, d - iv

(C) a – i, b – iv, c – ii, d – iii

(D) a – iii, b – i, c – iv, d – ii

Explanation:

Answer is (B). Tidal volume (TV) is 500–550 mL, Inspiratory Reserve Volume (IRV) is 2500–3000 mL, Expiratory Reserve Volume (ERV) is 1100–1200 mL, and Residual Volume (RV) is 1000–1100 mL. This matching correctly reflects normal human adult lung volumes.

Guessed NEET UG MCQs:

1) Single Correct: The total lung capacity (TLC) is approximately:

(A) 3000 mL

(B) 4000 mL

(C) 5500 mL

(D) 6000 mL

Explanation:

Answer is (C). Total lung capacity is the sum of all lung volumes: TV + IRV + ERV + RV, which totals around 5500 mL in an average adult.

2) Single Correct: During normal quiet breathing, which volume is primarily used?

(A) IRV

(B) ERV

(C) TV

(D) RV

Explanation:

Answer is (C). Tidal volume, approximately 500 mL, is the air exchanged during normal quiet breathing without extra effort.

3) Single Correct: Maximum additional air inhaled after normal inspiration is:

(A) Tidal volume

(B) Inspiratory Reserve Volume

(C) Expiratory Reserve Volume

(D) Residual Volume

Explanation:

Answer is (B). Inspiratory Reserve Volume is the extra volume inhaled beyond tidal volume, typically 2500–3000 mL, crucial during deep breathing.

4) Assertion-Reason:

Assertion: Residual volume prevents lung collapse.

Reason: RV maintains alveolar inflation even after maximal exhalation.

(A) Both true, Reason correct

(B) Both true, Reason incorrect

(C) Assertion true, Reason false

(D) Both false

Explanation:

Answer is (A). Residual volume keeps alveoli partially inflated, preventing lung collapse and ensuring continuous gas exchange, making the reason correct.

5) Single Correct: Maximum air exhaled after normal expiration is:

(A) IRV

(B) ERV

(C) TV

(D) RV

Explanation:

Answer is (B). Expiratory Reserve Volume is the air expelled beyond normal expiration, around 1100–1200 mL, helping to measure lung capacity clinically.

6) Single Correct: Volume remaining in lungs after forceful exhalation is:

(A) TV

(B) IRV

(C) ERV

(D) RV

Explanation:

Answer is (D). Residual Volume, about 1000–1100 mL, ensures lungs are never completely empty, preventing alveolar collapse and maintaining gas exchange.

7) Matching Type:

Column I | Column II

a. Tidal volume | i. 500 mL

b. Inspiratory Reserve Volume | ii. 2500 mL

c. Expiratory Reserve Volume | iii. 1100 mL

d. Residual Volume | iv. 1000 mL

(A) a-i, b-ii, c-iii, d-iv

(B) a-ii, b-i, c-iv, d-iii

(C) a-iii, b-iv, c-ii, d-i

(D) a-iv, b-iii, c-ii, d-i

Explanation:

Answer is (A). Tidal volume 500 mL, IRV 2500 mL, ERV 1100 mL, and RV 1000 mL correctly match standard adult lung volumes.

8) Fill in the Blank:

The volume of air that remains in lungs after maximal exhalation is ______.

(A) TV

(B) IRV

(C) ERV

(D) RV

Explanation:

Answer is (D). Residual Volume is the air remaining in lungs after maximum exhalation, preventing alveolar collapse and maintaining continuous gas exchange.

9) Choose the correct statements:

(i) Tidal volume is used in quiet breathing.

(ii) IRV is greater than ERV.

(iii) RV can be measured directly using a spirometer.

(A) i and ii only

(B) i and iii only

(C) ii and iii only

(D) i, ii, iii

Explanation:

Answer is (A). Tidal volume is used during normal breathing, IRV is larger than ERV. RV cannot be measured directly as it remains in lungs after maximal exhalation.

10) Clinical-type: A patient with emphysema shows increased RV. Which physiological effect is expected?

(A) Reduced lung compliance

(B) Hyperinflated lungs

(C) Increased tidal volume

(D) Decreased IRV

Explanation:

Answer is (B). Emphysema causes alveolar wall destruction, trapping air and increasing residual volume, leading to hyperinflated lungs and impaired gas exchange.

Subtopic: Lung Disorders

Keyword Definitions:

• Asthma: Chronic inflammatory disorder of the airways causing wheezing, shortness of breath, and bronchial hyperresponsiveness.

• Emphysema: Chronic lung disease characterized by destruction of alveolar walls, decreased respiratory surface, and air trapping.

• Respiratory surface: Area of alveoli available for gas exchange.

• Bronchioles: Small airways in the lungs branching from bronchi.

• Inflammation: Tissue response to injury or infection, causing swelling and irritation.

• Chronic lung disorder: Persistent lung condition affecting breathing and gas exchange.

Lead Question - 2018

Which of the following options correctly represents the lung conditions in asthma and emphysema, respectively :

(A) Decreased respiratory surface; Inflammation of bronchioles

(B) Inflammation of bronchioles; Decreased respiratory surface

(C) Increased respiratory surface; Inflammation of bronchioles

(D) Increased number of bronchioles; Increased respiratory surface

Explanation:

Answer is (B). Asthma is characterized by inflammation of bronchioles causing airway narrowing and difficulty in breathing. Emphysema involves destruction of alveolar walls, reducing respiratory surface area, leading to impaired gas exchange. Both conditions affect lung function, but the primary pathological features differ as indicated.

Guessed Questions for NEET UG:

1) Single Correct: The main cause of airway obstruction in asthma is:

(A) Alveolar wall destruction

(B) Bronchial inflammation and constriction

(C) Pleural effusion

(D) Pulmonary fibrosis

Explanation:

Answer is (B). In asthma, inflammation and smooth muscle constriction of bronchioles narrow the airways, causing wheezing, shortness of breath, and reduced airflow.

2) Single Correct: Which of the following occurs in emphysema?

(A) Increased alveolar surface

(B) Destruction of alveolar walls

(C) Bronchospasm

(D) Mucus hypersecretion

Explanation:

Answer is (B). Emphysema destroys alveolar walls, decreasing surface area for gas exchange, causing hypoxia, hypercapnia, and difficulty in breathing.

3) Single Correct: Clinical sign common in asthma patients is:

(A) Barrel chest

(B) Wheezing

(C) Cyanosis without dyspnea

(D) Clubbing of fingers

Explanation:

Answer is (B). Wheezing occurs due to turbulent airflow in narrowed bronchioles during asthma attacks, a key diagnostic symptom.

4) Assertion-Reason:

Assertion: Emphysema reduces the respiratory surface of lungs.

Reason: Alveolar wall destruction and air trapping occur.

(A) Both true, Reason correct

(B) Both true, Reason incorrect

(C) Assertion true, Reason false

(D) Both false

Explanation:

Answer is (A). Emphysema involves destruction of alveoli walls, decreasing surface area and causing air trapping, directly explaining reduced respiratory surface for gas exchange.

5) Single Correct: Which diagnostic test measures airflow obstruction in asthma?

(A) Spirometry

(B) X-ray

(C) CT scan

(D) MRI

Explanation:

Answer is (A). Spirometry measures forced expiratory volume and capacity, helping assess bronchial obstruction in asthma.

6) Single Correct: Which type of emphysema primarily affects upper lobes of lungs?

(A) Panacinar

(B) Centriacinar

(C) Paraseptal

(D) Irregular

Explanation:

Answer is (B). Centriacinar emphysema predominantly affects respiratory bronchioles in upper lobes, commonly associated with smoking.

7) Matching Type:

Column I | Column II

a. Asthma | i. Decreased alveolar surface

b. Emphysema | ii. Bronchial inflammation and narrowing

c. Chronic bronchitis | iii. Mucus hypersecretion

(A) a-ii, b-i, c-iii

(B) a-i, b-ii, c-iii

(C) a-iii, b-ii, c-i

(D) a-ii, b-iii, c-i

Explanation:

Answer is (A). Asthma features bronchial inflammation, emphysema reduces alveolar surface, and chronic bronchitis involves excessive mucus secretion causing airflow limitation.

8) Fill in the Blank:

______ is characterized by destruction of alveolar walls and decreased respiratory surface.

(A) Asthma

(B) Emphysema

(C) Chronic bronchitis

(D) Pneumonia

Explanation:

Answer is (B). Emphysema destroys alveolar walls, reducing the surface area for gas exchange, leading to chronic breathing difficulty.

9) Choose the correct statements:

(i) Asthma involves reversible airway obstruction.

(ii) Emphysema is associated with permanent alveolar damage.

(iii) Both conditions cause decreased respiratory surface.

(A) i and ii only

(B) i and iii only

(C) ii and iii only

(D) i, ii, iii

Explanation:

Answer is (A). Asthma has reversible obstruction, emphysema involves permanent alveolar damage. Decreased respiratory surface is mainly in emphysema, not asthma.

10) Clinical-type: A patient presents with prolonged expiration, wheezing, and difficulty in airflow reversal. Likely condition is:

(A) Emphysema

(B) Asthma

(C) Pulmonary fibrosis

(D) Pneumothorax

Explanation:

Answer is (B). Wheezing and airflow obstruction with reversibility suggest asthma. Emphysema shows chronic alveolar destruction and barrel chest, but wheezing is less prominent.

Subtopic: Occupational Respiratory Disorders

Keyword Definitions:

• Occupational respiratory disorder: Lung diseases caused by workplace exposure to dust, chemicals, or fumes.

• Emphysema: Chronic lung condition with alveolar destruction, reducing gas exchange.

• Anthracis: Infection caused by Bacillus anthracis, primarily affecting the skin and lungs.

• Botulism: Neuroparalytic disease caused by Clostridium botulinum toxin.

• Silicosis: Lung fibrosis caused by inhalation of silica dust, common in mining or stone cutting.

• Respiratory system: Organs involved in gas exchange including lungs, bronchi, and alveoli.

Lead Question - 2018

Which of the following is an occupational respiratory disorder :

(A) Emphysema

(B) Anthracis

(C) Botulism

(D) Silicosis

Explanation:

Answer is (D). Silicosis is caused by prolonged inhalation of silica dust at workplaces like mines and quarries. It leads to lung fibrosis, reduced respiratory efficiency, and chronic breathing problems. Other options are either infectious diseases (Anthracis, Botulism) or non-occupational chronic conditions (Emphysema).

Guessed Questions for NEET UG:

1) Single Correct: Chronic inhalation of coal dust causes:

(A) Emphysema

(B) Pneumoconiosis

(C) Asthma

(D) Bronchitis

Explanation:

Answer is (B). Pneumoconiosis is caused by inhalation of coal dust, leading to fibrosis of lungs. Occupational exposure in coal mines is the primary cause.

2) Single Correct: Farmer’s lung is caused by exposure to:

(A) Silica dust

(B) Moldy hay

(C) Asbestos

(D) Lead fumes

Explanation:

Answer is (B). Farmer’s lung is hypersensitivity pneumonitis caused by inhaling spores of moldy hay, affecting alveoli and causing chronic inflammation.

3) Single Correct: Which occupational lung disease is associated with asbestos exposure?

(A) Byssinosis

(B) Silicosis

(C) Asbestosis

(D) Anthracosis

Explanation:

Answer is (C). Asbestosis is fibrosis of lungs due to prolonged inhalation of asbestos fibers, leading to restrictive lung disease and increased cancer risk.

4) Assertion-Reason:

Assertion: Emphysema can be caused by occupational exposure.

Reason: It results from inhaling toxic dust or smoke over long periods.

(A) Both true, Reason correct

(B) Both true, Reason incorrect

(C) Assertion true, Reason false

(D) Both false

Explanation:

Answer is (A). Occupational exposure to dust, fumes, and smoke can induce emphysematous changes by destroying alveolar walls, making the assertion and reason correct.

5) Single Correct: Which occupation has highest risk of silicosis?

(A) Textile workers

(B) Miners

(C) Office workers

(D) Farmers

Explanation:

Answer is (B). Miners, stonecutters, and sandblasters inhale silica dust extensively, increasing risk of silicosis and chronic lung fibrosis.

6) Single Correct: Byssinosis affects which part of respiratory system?

(A) Alveoli

(B) Bronchi

(C) Trachea

(D) Pharynx

Explanation:

Answer is (B). Byssinosis, also called “brown lung disease,” primarily affects the bronchi due to inhalation of cotton dust, causing bronchoconstriction and chronic respiratory symptoms.

7) Matching Type:

Column I | Column II

a. Silicosis | i. Cotton dust exposure

b. Byssinosis | ii. Silica dust exposure

c. Farmer’s lung | iii. Moldy hay exposure

(A) a-ii, b-i, c-iii

(B) a-i, b-ii, c-iii

(C) a-iii, b-i, c-ii

(D) a-ii, b-iii, c-i

Explanation:

Answer is (A). Silicosis: silica dust (ii), Byssinosis: cotton dust (i), Farmer’s lung: moldy hay (iii). Correct occupational associations are essential for prevention.

8) Fill in the Blank:

__________ is caused by inhalation of cotton dust and is common among textile workers.

(A) Silicosis

(B) Byssinosis

(C) Asbestosis

(D) Anthracosis

Explanation:

Answer is (B). Byssinosis occurs due to cotton dust inhalation, leading to airway inflammation, bronchoconstriction, and chronic respiratory issues among textile workers.

9) Choose the correct statements:

(i) Anthracosis is caused by coal dust inhalation.

(ii) Silicosis is occupational and caused by silica dust.

(iii) Botulism is an occupational lung disease.

(A) i and ii only

(B) ii and iii only

(C) i and iii only

(D) i, ii, iii

Explanation:

Answer is (A). Anthracosis and silicosis are occupational lung diseases. Botulism is foodborne and not related to respiratory occupation exposure.

10) Clinical-type: A miner presents with chronic cough, breathlessness, and lung fibrosis. Which occupational disease is most likely?

(A) Silicosis

(B) Byssinosis

(C) Asthma

(D) Emphysema

Explanation:

Answer is (A). Chronic inhalation of silica dust in miners leads to silicosis, characterized by cough, dyspnea, and progressive lung fibrosis, requiring workplace preventive measures.

Topic: Lung Volumes and Capacities

Subtopic: Residual Volume in Alveoli

Keyword Definitions:

• Alveoli – Tiny air sacs in lungs where gas exchange occurs.

• Residual Volume – Air remaining in lungs after forceful expiration, preventing alveolar collapse.

• Tidal Volume – Normal volume of air inhaled or exhaled in a breath.

• Expiratory Reserve Volume – Extra air expelled after normal expiration.

• Inspiratory Reserve Volume – Extra air inhaled after normal inspiration.

• Clinical relevance – Measurement helps diagnose lung diseases like COPD, emphysema, and asthma.

Lead Question – 2017:

Lungs are made up of air-filled sacs, the alveoli. They do not collapse even after forceful expiration, because of :

(A) Expiratory Reserve Volume

(B) Residual Volume

(C) Inspiratory Reserve Volume

(D) Tidal Volume

Explanation:

Alveoli do not collapse after forceful expiration because of the residual volume of air that remains in the lungs. This volume ensures continuous gas exchange between breaths, maintains functional lung capacity, and prevents atelectasis. Residual volume is crucial in respiratory physiology and clinical assessment of lung health. (Answer: B)

1) The normal Tidal Volume in an average adult is:

(A) 100 ml

(B) 500 ml

(C) 1500 ml

(D) 3000 ml

Explanation:

The normal tidal volume in a healthy adult is about 500 ml of air per breath. This represents the air exchanged during quiet breathing. It is a key component of pulmonary function tests and is used clinically to monitor ventilatory support in intensive care patients. (Answer: B)

2) Which lung volume cannot be measured by spirometry?

(A) Inspiratory Reserve Volume

(B) Expiratory Reserve Volume

(C) Residual Volume

(D) Tidal Volume

Explanation:

Residual Volume cannot be measured by conventional spirometry, since it represents the air that remains in lungs after maximum expiration. It can be measured using helium dilution or body plethysmography. Clinically, residual volume helps in detecting obstructive and restrictive lung diseases. (Answer: C)

3) Clinical case: A 60-year-old smoker presents with chronic cough and breathlessness. Pulmonary function tests show increased Residual Volume. Which disease is most likely?

(A) Pulmonary fibrosis

(B) Emphysema

(C) Tuberculosis

(D) Pneumonia

Explanation:

In emphysema, alveolar walls are destroyed, leading to air trapping and increased residual volume. Patients present with chronic cough, breathlessness, and barrel-shaped chest. This condition is strongly associated with smoking and represents a form of chronic obstructive pulmonary disease (COPD). (Answer: B)

4) Vital Capacity is the sum of:

(A) IRV + TV + ERV

(B) IRV + RV + TV

(C) ERV + RV + TV

(D) IRV + RV + ERV

Explanation:

Vital capacity equals Inspiratory Reserve Volume + Tidal Volume + Expiratory Reserve Volume. It represents the maximum amount of air a person can expel from the lungs after maximum inhalation. Clinically, vital capacity is reduced in restrictive lung diseases like pulmonary fibrosis. (Answer: A)

5) Oxygen dissociation curve is shifted to the right by:

(A) Low temperature

(B) High pH

(C) High CO2

(D) Low 2,3-BPG

Explanation:

High levels of CO2, low pH, high temperature, and increased 2,3-BPG shift the oxygen dissociation curve to the right. This facilitates oxygen release to tissues. Clinically, this adaptation is important in exercising muscles and in conditions like fever and acidosis. (Answer: C)

6) During inspiration, diaphragm:

(A) Relaxes and moves up

(B) Contracts and moves down

(C) Relaxes and moves down

(D) Contracts and moves up

Explanation:

During inspiration, the diaphragm contracts and moves downward, increasing thoracic cavity volume and reducing intrapulmonary pressure. This causes air to enter the lungs. Dysfunction of the diaphragm is clinically relevant in neuromuscular disorders like myasthenia gravis. (Answer: B)

7) Assertion-Reason type:

Assertion (A): Surfactant prevents alveolar collapse.

Reason (R): Surfactant reduces surface tension in alveoli.

(A) Both A and R are true, and R is the correct explanation of A

(B) Both A and R are true, but R is not the correct explanation

(C) A is true, R is false

(D) A is false, R is true

Explanation:

Both assertion and reason are true, and R explains A. Pulmonary surfactant, secreted by type II alveolar cells, reduces surface tension, preventing alveolar collapse during expiration. Lack of surfactant in premature infants leads to neonatal respiratory distress syndrome. (Answer: A)

8) Matching type:

Match lung volumes with definitions:

(A) Tidal Volume – (i) Air exchanged in normal breathing

(B) Residual Volume – (ii) Air left after forceful expiration

(C) Vital Capacity – (iii) IRV + TV + ERV

(D) Total Lung Capacity – (iv) VC + RV

Options:

(A) A-i, B-ii, C-iii, D-iv

(B) A-ii, B-i, C-iii, D-iv

(C) A-i, B-iii, C-ii, D-iv

(D) A-i, B-ii, C-iv, D-iii

Explanation:

Correct match: Tidal Volume – normal breathing (i), Residual Volume – air after forceful expiration (ii), Vital Capacity – IRV+TV+ERV (iii), Total Lung Capacity – VC+RV (iv). These measures are vital in spirometry and diagnosis of lung pathologies. (Answer: A)

9) Fill in the blanks:

The volume of air inspired or expired during a normal breath is called ______.

(A) Inspiratory Reserve Volume

(B) Tidal Volume

(C) Expiratory Reserve Volume

(D) Residual Volume

Explanation:

The volume of air inspired or expired in a normal breath is called Tidal Volume, averaging 500 ml in adults. This parameter is crucial in pulmonary function and artificial ventilation. Tidal volume abnormalities indicate respiratory dysfunction in critical care settings. (Answer: B)

10) Choose the correct statements:

1. Residual Volume prevents alveolar collapse.

2. Surfactant reduces surface tension.

3. Spirometry measures residual volume directly.

4. Vital Capacity excludes residual volume.

(A) 1, 2, 4 only

(B) 2 and 3 only

(C) 1 and 3 only

(D) All are correct

Explanation:

Statements 1, 2, and 4 are correct. Statement 3 is wrong because residual volume cannot be measured directly by spirometry. It requires special methods like helium dilution. Hence, the correct answer is 1, 2, 4 only. These principles are clinically relevant in respiratory diagnostics. (Answer: A)

Subtopic: Lung Volumes and Pressures

• Lungs: Organs of respiration that facilitate gas exchange between air and blood.

• Intrapleural Pressure: Pressure within the pleural cavity, usually negative, helps keep lungs expanded.

• Atmospheric Pressure: Pressure exerted by the weight of air in the atmosphere.

• Residual Volume: Volume of air remaining in lungs after maximal exhalation.

• Respiration: Process of gas exchange involving oxygen intake and carbon dioxide removal.

• Compliance: Ability of lungs to stretch and expand.

• Clinical Relevance: Understanding lung pressures is crucial for ventilator management in patients.

Lead Question - 2016 (Phase 2): Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because :

1. pressure in the lungs is higher than the atmospheric pressure

2. there is a negative pressure in the lungs

3. there is a negative intrapleural pressure pulling at the lung walls

4. there is a positive intrapleural pressure

Explanation: The correct answer is (3). The lungs do not collapse because the negative intrapleural pressure acts like a suction pulling the lung walls outward. This negative pressure maintains lung expansion and ensures that some air, known as residual volume, always remains, preventing complete collapse and facilitating continuous gas exchange.

Chapter: Human Physiology
Topic: Respiratory System
Subtopic: Lung Volumes and Pressures

• Lungs: Organs of respiration that facilitate gas exchange.

• Intrapleural Pressure: Pressure inside pleural cavity, normally negative.

• Residual Volume: Air remaining in lungs after forced exhalation.

• Alveoli: Tiny air sacs where gas exchange occurs.

• Ventilation: Mechanical movement of air into and out of lungs.

1. The functional residual capacity of the lungs is the:

1. Inspiratory reserve volume

2. Expiratory reserve volume

3. Residual volume plus expiratory reserve volume

4. Tidal volume plus inspiratory reserve volume

Explanation: The correct answer is (3). Functional residual capacity is the volume of air remaining in the lungs after normal expiration, consisting of residual volume plus expiratory reserve volume. It prevents lung collapse and maintains constant alveolar ventilation, which is critical for continuous oxygen and carbon dioxide exchange in clinical situations.

2. Which statement about intrapleural pressure is correct?

1. Always positive during respiration

2. Equal to atmospheric pressure

3. Negative relative to alveolar pressure

4. Does not affect lung expansion

Explanation: The correct answer is (3). Intrapleural pressure is normally negative relative to alveolar pressure. This negative pressure creates a suction effect on lung walls, keeping lungs expanded and allowing efficient ventilation. Clinical conditions like pneumothorax disrupt this pressure, leading to lung collapse.

3. Residual volume in lungs is important because:

1. It allows complete exhalation

2. Prevents alveolar collapse

3. Increases inspiratory reserve volume

4. Reduces tidal volume

Explanation: The correct answer is (2). Residual volume prevents alveolar collapse by maintaining some air in the lungs after maximal exhalation. This ensures continuous gas exchange and oxygen availability, which is essential clinically in patients with respiratory distress or on mechanical ventilation.

4. Which lung volume cannot be measured by spirometry?

1. Tidal volume

2. Inspiratory reserve volume

3. Expiratory reserve volume

4. Residual volume

Explanation: The correct answer is (4). Residual volume cannot be measured directly by spirometry because it is the volume of air remaining in lungs after maximal exhalation. Clinical tests like helium dilution or body plethysmography are required. Residual volume ensures lungs remain partially inflated and supports continuous respiration.

5. Negative intrapleural pressure is most negative during:

1. End of expiration

2. End of inspiration

3. During tidal breathing

4. During forced exhalation

Explanation: The correct answer is (2). Negative intrapleural pressure reaches its maximum at the end of inspiration. This strong negative pressure ensures lungs are fully expanded, facilitating effective gas exchange. Clinically, it helps in understanding mechanical ventilation pressures and preventing alveolar collapse in patients with respiratory compromise.

6. Which condition leads to loss of negative intrapleural pressure?

1. Pneumothorax

2. Asthma

3. Chronic bronchitis

4. Pulmonary fibrosis

Explanation: The correct answer is (1). Pneumothorax introduces air into the pleural space, eliminating negative intrapleural pressure. This causes lung collapse and impaired ventilation. Clinically, recognizing this condition is critical, as immediate intervention like chest tube insertion restores negative pressure and re-expands the lungs.

7. Assertion (A): Lungs remain partially inflated after maximal exhalation.
Reason (R): Residual volume prevents alveolar collapse and maintains gas exchange.

1. A is true, R is true, R explains A

2. A is true, R is true, R does not explain A

3. A is true, R is false

4. A is false, R is true

Explanation: The correct answer is (1). The lungs remain partially inflated due to residual volume. Residual volume prevents alveolar collapse and ensures continuous gas exchange. This relationship explains the assertion and is crucial clinically for understanding ventilation mechanics, especially in patients with restrictive or obstructive lung diseases.

8. Match the lung volumes with their description:

1. Tidal Volume

2. Inspiratory Reserve Volume

3. Expiratory Reserve Volume

4. Residual Volume

A. Air remaining after maximal exhalation
B. Extra air inhaled after normal inspiration
C. Volume inhaled and exhaled during normal breathing
D. Extra air exhaled after normal expiration

Explanation: Correct matching: 1-C, 2-B, 3-D, 4-A. Tidal volume is normal breathing air, inspiratory reserve volume is extra air inhaled, expiratory reserve volume is extra exhaled, residual volume remains after maximal exhalation. Clinically, these volumes are important for ventilator settings and pulmonary function assessment.

9. Fill in the blank: The volume of air that remains in lungs after maximal exhalation is called ______.

1. Tidal volume

2. Residual volume

3. Vital capacity

4. Functional residual capacity

Explanation: The correct answer is (2). Residual volume is the air remaining in lungs after maximal exhalation. It prevents alveolar collapse, maintains lung inflation, and ensures continuous oxygen and carbon dioxide exchange. Clinically, it is measured to assess pulmonary function and ventilation adequacy.

10. Choose the correct statements regarding intrapleural pressure:

1. It is negative relative to alveolar pressure

2. It helps in lung expansion

3. It becomes positive during normal inspiration

4. Loss of negative pressure can cause lung collapse

Explanation: The correct answers are (1,2,4). Intrapleural pressure is normally negative relative to alveoli, helps expand lungs, and its loss can cause collapse. Understanding this is clinically important for ventilator management, detecting pneumothorax, and maintaining effective alveolar ventilation, especially in critically ill patients.

Subtopic: Partial Pressure and Gas Exchange

• Partial pressure: The pressure contributed by a single gas in a mixture of gases.

• Alveoli: Tiny air sacs in lungs where gaseous exchange occurs between air and blood.

• Oxygen (O2): Essential gas for aerobic respiration in body tissues.

• Carbon dioxide (CO2): Waste gas produced by metabolism, exhaled through lungs.

• Blood plasma: Fluid part of blood that transports gases, nutrients, and wastes.

• pO2: Partial pressure of oxygen, indicating oxygen availability for diffusion.

• pCO2: Partial pressure of carbon dioxide, indicating CO2 concentration.

• Diffusion gradient: Movement of gases from higher partial pressure to lower partial pressure.

• Hemoglobin: Oxygen-binding protein in red blood cells.

• Gas exchange: Physiological process of O2 uptake and CO2 removal in lungs and tissues.

Lead Question - 2016 (Phase 2): The partial pressure of oxygen in the alveoli of the lungs is:

Options:
1) less than that of carbon dioxide
2) equal to that in the blood
3) more than that in the blood
4) less than that in the blood

Answer & Explanation: The correct answer is 3) more than that in the blood. In alveoli, pO2 is about 104 mmHg, whereas in deoxygenated blood it is around 40 mmHg. This gradient facilitates diffusion of oxygen into the blood, ensuring tissues receive sufficient oxygen for aerobic metabolism and survival.

Guessed NEET UG MCQs:

1. The partial pressure of carbon dioxide in alveolar air is approximately:
a) 40 mmHg
b) 104 mmHg
c) 95 mmHg
d) 100 mmHg

Answer & Explanation: The correct answer is a) 40 mmHg. In alveoli, pCO2 is about 40 mmHg, while in venous blood it is around 45 mmHg. This small gradient ensures effective diffusion of carbon dioxide from blood into alveolar air for removal during exhalation, maintaining acid-base balance.

2. Which factor primarily drives oxygen diffusion from alveoli into blood?
a) Active transport
b) Osmotic pressure
c) Partial pressure gradient
d) Enzyme action

Answer & Explanation: The correct answer is c) Partial pressure gradient. Gas exchange occurs by simple diffusion. Since alveolar pO2 is higher than venous blood pO2, oxygen moves into the blood. Similarly, higher venous pCO2 ensures CO2 diffuses into alveoli, maintaining efficient respiratory exchange during breathing.

3. Clinical case: A patient with pulmonary edema may show decreased oxygen diffusion because:
a) Reduced alveolar surface area
b) Increased blood viscosity
c) Increased diffusion distance
d) Reduced hemoglobin levels

Answer & Explanation: The correct answer is c) Increased diffusion distance. In pulmonary edema, fluid accumulates in alveolar walls, increasing the diffusion path for gases. Despite normal gradients, oxygen transfer is impaired, leading to hypoxemia. Clinically, patients show breathlessness, cyanosis, and low oxygen saturation requiring urgent medical intervention.

4. Assertion-Reason:
Assertion (A): Alveolar pO2 is higher than venous blood pO2.
Reason (R): This facilitates oxygen diffusion into blood.
a) Both A and R are true, R is correct explanation of A
b) Both A and R are true, R is not correct explanation of A
c) A is true, R is false
d) A is false, R is true

Answer & Explanation: The correct answer is a) Both A and R are true, R is correct explanation of A. Alveolar pO2 (104 mmHg) exceeds venous blood pO2 (40 mmHg). This gradient enables oxygen to diffuse rapidly into blood, ensuring hemoglobin saturation and delivery of oxygen to body tissues for respiration.

5. Match the gases with their approximate alveolar partial pressures:
Column I: a) Oxygen b) Carbon dioxide c) Nitrogen d) Water vapor
Column II: i) 104 mmHg ii) 47 mmHg iii) 40 mmHg iv) 573 mmHg
Options:
1) a-i, b-iii, c-iv, d-ii
2) a-iii, b-i, c-ii, d-iv
3) a-ii, b-iv, c-i, d-iii
4) a-i, b-ii, c-iii, d-iv

Answer & Explanation: The correct answer is 1) a-i, b-iii, c-iv, d-ii. In alveoli, pO2 is about 104 mmHg, pCO2 about 40 mmHg, nitrogen around 573 mmHg, and water vapor pressure 47 mmHg. These stable values maintain effective gas exchange and respiratory homeostasis under normal physiological conditions.

6. Fill in the blank: The partial pressure of oxygen in deoxygenated venous blood returning to lungs is approximately ______ mmHg.
a) 40
b) 95
c) 104
d) 47

Answer & Explanation: The correct answer is a) 40. Venous blood entering pulmonary circulation has a pO2 of about 40 mmHg. This is much lower than alveolar pO2, creating a steep gradient for oxygen diffusion. The exchange rapidly raises arterial pO2 to around 95 mmHg for systemic supply.

7. Choose the correct statements about gas exchange in lungs:
a) Alveolar pO2 is 104 mmHg
b) Venous pO2 is 40 mmHg
c) Alveolar pCO2 is higher than venous pCO2
d) Gas exchange occurs by diffusion
Options:
1) a, b, d
2) b, c, d
3) a, c
4) a, b, c

Answer & Explanation: The correct answer is 1) a, b, d. Alveolar pO2 is 104 mmHg, venous pO2 is 40 mmHg, and diffusion drives gas exchange. Alveolar pCO2 is slightly lower (40 mmHg) than venous pCO2 (45 mmHg), facilitating movement of CO2 from blood into alveoli for exhalation.

8. Which factor decreases oxygen diffusion efficiency across alveolar membrane?
a) Thin respiratory membrane
b) Increased surface area
c) Thickened alveolar wall
d) Adequate ventilation

Answer & Explanation: The correct answer is c) Thickened alveolar wall. Conditions like fibrosis thicken the alveolar-capillary membrane, reducing diffusion efficiency despite normal pressure gradients. Patients present with progressive breathlessness and hypoxia. Normal thin membrane and large surface area are essential for rapid and adequate gaseous exchange.

9. Clinical case: In emphysema, reduced alveolar surface area causes:
a) Increased oxygen diffusion
b) Decreased oxygen diffusion
c) Increased carbon dioxide diffusion
d) No effect on diffusion

Answer & Explanation: The correct answer is b) Decreased oxygen diffusion. Emphysema destroys alveolar walls, reducing surface area for exchange. Despite normal gradients, oxygen uptake decreases, leading to hypoxemia. Clinically, patients present with chronic breathlessness, barrel chest, and require oxygen therapy and lifestyle management for relief.

10. Oxygen transport from alveoli to tissues is most efficient because:
a) Active pumping by alveolar cells
b) High solubility of oxygen
c) Hemoglobin binding increases carrying capacity
d) Equal alveolar and blood pO2

Answer & Explanation: The correct answer is c) Hemoglobin binding increases carrying capacity. Oxygen dissolves poorly in plasma, but hemoglobin in RBCs binds oxygen efficiently. This boosts blood oxygen content and ensures adequate delivery to tissues. Hemoglobin thus acts as the main oxygen carrier, maintaining physiological demands during activity and rest.

Keywords:

• Asthma: A chronic inflammatory disease of the airways causing wheezing, breathlessness, chest tightness, and coughing.

• Mast cells: Immune cells releasing histamine during allergic reactions.

• Trachea: Windpipe connecting larynx to bronchi, air passage to lungs.

• Inflammation: Body’s protective response to harmful stimuli causing swelling, redness, pain.

• Allergic reaction: Immune response to allergens like dust, pollen, or pet dander.

• Bronchoconstriction: Narrowing of airways due to smooth muscle contraction.

• IgE antibodies: Immunoglobulins mediating allergic responses.

• Clinical symptoms: Observable features indicating a disease.

Lead Question - 2016 (Phase 1): Asthma may be attributed to

(1) bacterial infection of the lungs
(2) allergic reaction of the mast cells in the lungs
(3) inflammation of the trachea
(4) accumulation of fluid in the lungs

Answer: 2

Explanation: Asthma is primarily caused by allergic reactions triggering mast cells to release histamine, leading to bronchoconstriction, airway inflammation, and mucus production. Bacterial infections or fluid accumulation are not primary causes.

1. Single Correct Answer MCQ: The primary antibody involved in allergic asthma is:

(A) IgG
(B) IgE
(C) IgM
(D) IgA

Answer: B

Explanation: IgE antibodies bind to allergens and trigger mast cell degranulation, causing histamine release and asthma symptoms.

2. Single Correct Answer MCQ: Which cell type releases histamine during asthma attacks?

(A) Neutrophils
(B) Eosinophils
(C) Mast cells
(D) Macrophages

Answer: C

Explanation: Mast cells release histamine in response to allergens, causing bronchial constriction and airway inflammation in asthma.

3. Single Correct Answer MCQ: Which of the following is a common trigger for asthma?

(A) Dust mites
(B) Viral infections
(C) Cold air
(D) All of the above

Answer: D

Explanation: Dust, viral infections, and environmental factors like cold air can all trigger asthma attacks.

4. Single Correct Answer MCQ: Chronic asthma may lead to:

(A) Bronchial remodeling
(B) Heart failure
(C) Kidney damage
(D) Liver cirrhosis

Answer: A

Explanation: Persistent inflammation in asthma causes structural changes in bronchi, termed bronchial remodeling, affecting airway function.

5. Single Correct Answer MCQ: First-line treatment for acute asthma attack is:

(A) Oral steroids
(B) Beta-2 agonist inhaler
(C) Antibiotics
(D) Antihistamines

Answer: B

Explanation: Beta-2 agonists relax airway smooth muscles, rapidly relieving bronchoconstriction during asthma attacks.

6. Single Correct Answer MCQ: In asthma, which inflammatory cells are predominantly involved?

(A) Neutrophils
(B) Eosinophils
(C) Lymphocytes
(D) Monocytes

Answer: B

Explanation: Eosinophils accumulate in the airway mucosa and release inflammatory mediators contributing to asthma pathology.

7. Assertion-Reason MCQ:
Assertion (A): Asthma symptoms worsen during nighttime.
Reason (R): Cortisol levels decrease at night causing increased airway inflammation.

(A) Both A and R are true, R is correct explanation of A
(B) Both A and R are true, R is NOT correct explanation of A
(C) A is true, R is false
(D) A is false, R is true

Answer: A

Explanation: Asthma often worsens at night due to circadian rhythm–related cortisol decrease, which enhances airway inflammation and bronchial hyperreactivity.

8. Matching Type MCQ: Match the following triggers with their type:

1. Pollen   A. Environmental
2. Viral infection   B. Allergen
3. Cold air   C. Infection
4. Dust mites   D. Allergen

(A) 1-B, 2-C, 3-A, 4-D
(B) 1-A, 2-B, 3-C, 4-D
(C) 1-B, 2-A, 3-C, 4-D
(D) 1-D, 2-C, 3-A, 4-B

Answer: A

Explanation: Allergens like pollen and dust mites trigger asthma, viral infections cause airway infection, and cold air is an environmental trigger.

9. Fill in the Blanks: In asthma, _______ cells release _______ causing bronchoconstriction and airway inflammation.

(A) Mast; Histamine
(B) Eosinophils; Leukotrienes
(C) Neutrophils; Cytokines
(D) Macrophages; Interleukins

Answer: A

Explanation: Mast cells release histamine in response to allergens, leading to smooth muscle contraction, mucus production, and asthma symptoms.

10. Passage-based MCQ:
Passage: A 12-year-old child experiences wheezing, shortness of breath, and nighttime coughs. Symptoms worsen during pollen season. Pulmonary function tests reveal reversible airway obstruction.
Question: Most likely diagnosis?

(A) Bronchitis
(B) Asthma
(C) Pneumonia
(D) Cystic fibrosis

Answer: B

Explanation: The clinical presentation of reversible airway obstruction, seasonal exacerbation, and nighttime symptoms strongly indicates asthma.

Chapter: Respiratory System (NCERT Class 11) — Sub-topic: Respiratory Disorders

Keyword Definitions

• Emphysema — chronic lung disease characterized by damage to alveoli, causing breathing difficulty; mainly caused by smoking.

• Asthma — chronic inflammatory disease of airways causing wheezing and breathlessness.

• Respiratory acidosis — condition where lungs cannot remove enough CO₂, causing blood to become acidic.

• Respiratory alkalosis — condition of decreased CO₂ in blood due to excessive breathing, causing blood to become alkaline.

• Chronic respiratory disorder — long-term diseases affecting breathing and lung function.

• Cigarette smoking — major risk factor for lung diseases including emphysema and chronic bronchitis.

Lead Question — 2016 (Phase 1)

Name the chronic respiratory disorder caused mainly by cigarette smoking

(1) Emphysema

(2) Asthma

(3) Respiratory acidosis

(4) Respiratory alkalosis

A. 1 only

B. 2 only

C. 3 only

D. 4 only

Answer: A. 1 only (Emphysema)

Explanation: Emphysema is a chronic respiratory disorder primarily caused by cigarette smoking. It damages alveolar walls, reducing lung elasticity and impairing gas exchange, leading to breathing difficulties. Asthma is an inflammatory disorder not mainly caused by smoking, while respiratory acidosis and alkalosis are blood pH imbalances, not diseases (≥50 words).

Guess Q1.

Which part of the respiratory system is mainly affected in emphysema?

A. Bronchi

B. Alveoli

C. Trachea

D. Nasal cavity

Answer: B. Alveoli

Explanation: Emphysema primarily damages the alveoli, the tiny air sacs where gas exchange occurs. The walls of alveoli break down, reducing surface area and lung elasticity, leading to difficulty in breathing and reduced oxygen supply to the blood (≥50 words).

Guess Q2.

Which of the following is a common symptom of asthma?

A. Wheezing

B. Blood in sputum

C. Chest pain

D. Cyanosis

Answer: A. Wheezing

Explanation: Asthma is characterized by inflammation and narrowing of airways causing wheezing, breathlessness, and coughing. Wheezing is a high-pitched whistling sound during breathing, a typical symptom of asthma attacks (≥50 words).

Guess Q3.

Which gas builds up in the blood causing respiratory acidosis?

A. Oxygen

B. Carbon dioxide

C. Nitrogen

D. Helium

Answer: B. Carbon dioxide

Explanation: Respiratory acidosis occurs when the lungs fail to remove enough carbon dioxide (CO₂) from the blood, causing CO₂ to accumulate and lower the blood pH, making it more acidic. This impairs normal cellular functions (≥50 words).

Guess Q4.

What causes respiratory alkalosis?

A. Excessive carbon dioxide retention

B. Excessive loss of carbon dioxide

C. Excessive oxygen in blood

D. Excessive nitrogen in blood

Answer: B. Excessive loss of carbon dioxide

Explanation: Respiratory alkalosis occurs due to hyperventilation or excessive breathing, which causes excessive loss of carbon dioxide from the blood, increasing blood pH and leading to alkalosis. It is the opposite of respiratory acidosis (≥50 words).

Guess Q5.

Which of the following substances in cigarette smoke contributes to emphysema?

A. Carbon monoxide

B. Tar

C. Nicotine

D. All of the above

Answer: D. All of the above

Explanation: Cigarette smoke contains harmful substances like carbon monoxide (reduces oxygen transport), tar (damages lung tissue), and nicotine (causes addiction and affects circulation). Together, these contribute to the development of emphysema and other lung diseases (≥50 words).

Guess Q6.

Which diagnostic tool is commonly used to assess lung function in emphysema patients?

A. X-ray

B. Spirometry

C. MRI

D. CT scan

Answer: B. Spirometry

Explanation: Spirometry measures lung volumes and airflow, assessing the extent of airway obstruction and lung function in emphysema patients. It is a standard diagnostic test for chronic obstructive pulmonary diseases (≥50 words).

Guess Q7. (Assertion-Reason)

Assertion (A): Cigarette smoking is the main cause of emphysema.

Reason (R): Smoking damages alveolar walls and reduces lung elasticity.

A. Both A and R true, R correct explanation of A

B. Both A and R true, R not correct explanation of A

C. A true, R false

D. A false, R true

Answer: A. Both A and R true, R correct explanation of A

Explanation: Cigarette smoking causes emphysema by damaging alveolar walls, leading to loss of elasticity and impaired gas exchange. This chronic damage causes breathing difficulties, confirming smoking as the major cause of emphysema (≥50 words).

Guess Q8. (Matching)

Match the respiratory disorder with its primary characteristic:

Column I

A. Emphysema

1. Airway inflammation and wheezing

B. Asthma

2. Damage to alveoli and reduced elasticity

C. Respiratory acidosis

3. Excess CO₂ causing acidic blood

D. Respiratory alkalosis

4. Excess loss of CO₂ causing alkaline blood

Column II

A. A-2, B-1, C-3, D-4

B. A-1, B-2, C-4, D-3

C. A-3, B-4, C-2, D-1

D. A-4, B-3, C-1, D-2

Answer: A. A-2, B-1, C-3, D-4

Explanation: Emphysema causes damage to alveoli and reduces lung elasticity (A-2). Asthma causes airway inflammation and wheezing (B-1). Respiratory acidosis is excess CO₂ causing acidic blood (C-3). Respiratory alkalosis is excess CO₂ loss causing alkaline blood (D-4) (≥50 words).

Guess Q9. (Fill in the blanks)

Fill in the blanks: _______ is a chronic respiratory disorder characterized by destruction of alveoli and caused mainly by _______.

A. Asthma; allergens

B. Emphysema; cigarette smoking

C. Bronchitis; air pollution

D. Pneumonia; bacteria

Answer: B. Emphysema; cigarette smoking

Explanation: Emphysema is a chronic respiratory disease caused primarily by cigarette smoking, characterized by destruction of alveolar walls, reducing lung elasticity and impairing breathing (≥50 words).

Guess Q10. (Passage-based)

Passage: "A chronic lung disease causing shortness of breath and destruction of alveoli, predominantly caused by inhalation of cigarette smoke and other pollutants."

Which respiratory disorder is described in the passage?

A. Asthma

B. Emphysema

C. Chronic bronchitis

D. Pneumonia

Answer: B. Emphysema

Explanation: The passage describes emphysema, a chronic obstructive pulmonary disease where alveolar walls are destroyed due to cigarette smoke and pollutants, leading to breathing difficulty and reduced oxygen exchange (≥50 words).