Keyword Definitions:
Cuboidal epithelium – Epithelial cells shaped like cubes; typically involved in secretion and absorption.
Brush border – Dense layer of microvilli on the apical surface of epithelial cells to increase surface area.
Microvilli – Tiny finger-like projections on cell surface that enhance absorption and secretion.
Proximal convoluted tubule – Part of nephron in kidney responsible for reabsorption of water, ions, and nutrients.
Nephron – Functional unit of kidney that filters blood and produces urine.
Eustachian tube – Tube connecting middle ear to pharynx; helps equalize ear pressure.
Intestinal lining – Epithelium of small intestine, often columnar with microvilli for absorption.
Ducts of salivary glands – Channels that carry saliva from gland to oral cavity, lined by epithelial cells.
Absorption – Process of taking in substances from lumen into cells or blood.
Secretion – Release of substances like enzymes or mucus by cells.
Apical surface – Free surface of epithelial cell facing lumen or external environment.
Lead Question - 2020
Cuboidal epithelium with brush border of microvilli is found in:
(1) Proximal convoluted tubule of nephron
(2) Eustachian tube
(3) Lining of intestine
(4) Ducts of salivary glands
Explanation: The proximal convoluted tubule of nephron has cuboidal epithelial cells with a brush border of microvilli, increasing surface area for reabsorption of water, ions, and nutrients. Other structures listed have different epithelium types. Correct answer is (1) Proximal convoluted tubule of nephron.
1. Single Correct Answer: Microvilli primarily function to:
(1) Protect against abrasion
(2) Increase absorptive surface area
(3) Secrete hormones
(4) Support ciliary movement
Explanation: Microvilli are finger-like projections that significantly increase the apical surface area of epithelial cells, enhancing absorption and secretion efficiency, especially in kidneys and intestines. Correct answer is (2) Increase absorptive surface area.
2. Single Correct Answer: Cuboidal epithelium is commonly found in:
(1) Skin surface
(2) Kidney tubules
(3) Respiratory bronchioles
(4) Esophagus lining
Explanation: Cuboidal epithelium is found lining kidney tubules where it facilitates secretion and absorption, sometimes with a brush border to increase surface area. Correct answer is (2) Kidney tubules.
3. Single Correct Answer: The brush border is best observed in:
(1) Proximal convoluted tubule
(2) Distal convoluted tubule
(3) Collecting duct
(4) Glomerulus
Explanation: The proximal convoluted tubule has dense microvilli forming a brush border to maximize reabsorption of solutes and water. Correct answer is (1) Proximal convoluted tubule.
4. Assertion-Reason:
Assertion (A): Proximal convoluted tubule cells are cuboidal with brush border.
Reason (R): Brush border increases surface area for absorption of substances from filtrate.
(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: The proximal convoluted tubule cells are cuboidal and possess microvilli forming a brush border. This increases the surface area for reabsorption of water, ions, and nutrients from filtrate. Both assertion and reason are true, and R correctly explains A. Correct answer is (1).
5. Single Correct Answer: Which tubule has fewer microvilli compared to PCT?
(1) Distal convoluted tubule
(2) Loop of Henle
(3) Collecting duct
(4) All of the above
Explanation: Distal convoluted tubule cells have sparse microvilli compared to the proximal convoluted tubule, as their primary role is selective ion transport rather than massive reabsorption. Correct answer is (1) Distal convoluted tubule.
6. Single Correct Answer: Which epithelial type lines ducts of salivary glands?
(1) Simple cuboidal
(2) Simple columnar with microvilli
(3) Stratified squamous
(4) Transitional
Explanation: Ducts of salivary glands are lined by simple cuboidal epithelium, often without a brush border, allowing transport of saliva. Correct answer is (1) Simple cuboidal.
7. Matching Type: Match epithelial type with location:
a. Cuboidal with brush border – i. Proximal convoluted tubule
b. Columnar with microvilli – ii. Intestinal lining
c. Pseudostratified ciliated – iii. Eustachian tube
d. Stratified cuboidal – iv. Salivary gland ducts
Options:
(1) a-i, b-ii, c-iii, d-iv
(2) a-ii, b-i, c-iv, d-iii
(3) a-iii, b-ii, c-i, d-iv
(4) a-iv, b-iii, c-ii, d-i
Explanation: Cuboidal epithelium with brush border is in proximal convoluted tubule (a-i). Columnar with microvilli is in intestines (b-ii). Pseudostratified ciliated lines Eustachian tube (c-iii). Stratified cuboidal lines salivary ducts (d-iv). Correct answer is (1).
8. Fill in the blank: Microvilli increase ______ of epithelial cells.
(1) Strength
(2) Surface area
(3) Elasticity
(4) Thickness
Explanation: Microvilli are apical projections that increase the cell’s surface area, enhancing absorption and secretion efficiency in the kidney and intestine. Correct answer is (2) Surface area.
9. Single Correct Answer: In which part of nephron is most reabsorption of nutrients and water done?
(1) Distal convoluted tubule
(2) Proximal convoluted tubule
(3) Collecting duct
(4) Loop of Henle
Explanation: The proximal convoluted tubule reabsorbs about 65–70% of water, ions, and all glucose and amino acids from filtrate, aided by microvilli for increased surface area. Correct answer is (2) Proximal convoluted tubule.
10. Choose the correct statements:
(a) Proximal tubule cells have microvilli
(b) Distal tubule cells have brush border
(c) Salivary ducts have cuboidal epithelium
(d) Intestinal lining has columnar cells with microvilli
(1) a, c, d
(2) a, b, d
(3) b, c
(4) a, b, c, d
Explanation: Proximal tubule cells have microvilli (a). Salivary ducts are lined by cuboidal epithelium (c). Intestinal lining has columnar cells with microvilli (d). Distal tubule cells lack brush border (b is incorrect). Correct answer is (1) a, c, d.
Topic: Epithelium
Subtopic: Ciliated Epithelial Cells and Functions
Ciliated Epithelium: Epithelial tissue with hair-like structures (cilia) on the apical surface.
Cilia: Microscopic hair-like projections that move substances along the epithelial surface.
Mucus: Sticky secretion produced by goblet cells to trap particles and pathogens.
Bronchioles: Small branches of the bronchi in lungs conducting air to alveoli.
Fallopian Tubes: Tubes connecting ovaries to the uterus, aiding egg transport.
Particle Movement: Transport of dust, microbes, or debris along epithelial surfaces.
Directional Flow: Coordinated movement ensured by ciliary beating in one direction.
Epithelium: Tissue lining body cavities, ducts, and organs.
Respiratory Tract: Passage from nose/mouth to alveoli for air conduction.
Reproductive Tract: Pathways involved in gamete transport and fertilization.
Mucociliary Clearance: Mechanism of removing particles and pathogens from respiratory surfaces.
Lead Question (2019): The ciliated epithelial cells are required to move particles or mucus in a specific direction. In humans, these cells are mainly present in :
Options:
1. Bile duct and Bronchioles
2. Fallopian tubes and Pancreatic duct
3. Eustachian tube and Salivary duct
4. Bronchioles and Fallopian tubes
Explanation: Correct answer is 4. Ciliated epithelial cells are abundant in bronchioles and fallopian tubes. In bronchioles, they move mucus and trapped particles toward the pharynx. In fallopian tubes, they assist ovum transport toward the uterus. Coordinated ciliary beating ensures directional flow, contributing to respiratory defense and reproductive efficiency.
1. Single Correct Answer MCQ:
Which cells in respiratory tract produce mucus to trap particles?
Options:
a. Goblet cells
b. Ciliated cells
c. Squamous cells
d. Paneth cells
Explanation: Correct answer is a. Goblet cells secrete mucus, which traps dust, microbes, and other debris in the respiratory tract. Ciliated cells move this mucus, squamous cells are protective epithelium, and Paneth cells secrete antimicrobial peptides in the intestine. Mucus-goblet-cilia coordination maintains airway cleanliness and defense mechanisms.
2. Single Correct Answer MCQ:
Ciliary movement in fallopian tubes helps in:
Options:
a. Menstrual blood flow
b. Ovum transport
c. Hormone secretion
d. Fertilization at ovary
Explanation: Correct answer is b. Cilia in fallopian tubes beat in a coordinated manner to transport the ovum from the ovary toward the uterus. This ensures timely movement for potential fertilization. Ciliary action does not directly influence menstrual flow, hormone secretion, or fertilization within the ovary itself.
3. Single Correct Answer MCQ:
Ciliated epithelial cells are not abundant in which of the following?
Options:
a. Nasal cavity
b. Bronchioles
c. Fallopian tubes
d. Pancreatic duct
Explanation: Correct answer is d. Pancreatic ducts have simple cuboidal or columnar epithelium without motile cilia. Ciliated cells are abundant in nasal cavity, bronchioles, and fallopian tubes to facilitate directional flow of mucus or gametes, protecting tissues and assisting in reproductive transport efficiently.
4. Single Correct Answer MCQ:
The primary function of cilia in bronchioles is:
Options:
a. Gas exchange
b. Mucus movement
c. Secretion of surfactant
d. Absorption of nutrients
Explanation: Correct answer is b. Cilia in bronchioles beat rhythmically to move mucus, trapping dust and pathogens toward the throat for elimination. Gas exchange occurs in alveoli, surfactant secretion is by type II alveolar cells, and nutrient absorption is intestinal. Mucociliary clearance protects the respiratory system from infections.
5. Single Correct Answer MCQ:
Which type of epithelium lines the fallopian tubes?
Options:
a. Simple squamous
b. Pseudostratified columnar ciliated
c. Stratified cuboidal
d. Transitional
Explanation: Correct answer is b. Pseudostratified columnar ciliated epithelium lines the fallopian tubes, facilitating ovum transport. Simple squamous epithelium is for diffusion, stratified cuboidal is protective in ducts, and transitional epithelium is in urinary tract. Ciliary action ensures movement of gametes efficiently toward the uterus.
6. Single Correct Answer MCQ:
Ciliary dyskinesia leads to:
Options:
a. Impaired mucociliary clearance
b. Increased heart rate
c. Reduced hormone secretion
d. Hyperactive digestion
Explanation: Correct answer is a. Ciliary dyskinesia impairs ciliary beating, reducing mucus clearance in the respiratory tract. This results in recurrent infections and reduced airway hygiene. Heart rate, hormone secretion, and digestion are not directly affected by ciliary movement, highlighting the critical role of cilia in respiratory and reproductive health.
7. Assertion-Reason MCQ:
Assertion (A): Cilia in the respiratory tract move mucus toward the throat.
Reason (R): Cilia beat in a coordinated, directional manner.
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. Respiratory cilia move mucus upward toward the throat to clear debris and pathogens. Coordinated beating ensures unidirectional flow, preventing accumulation in the airways. Dysfunction disrupts mucociliary clearance, leading to infections. This mechanism illustrates the physiological importance of cilia in protecting the respiratory system.
8. Matching Type MCQ:
Match the ciliated structure with its location:
Column-I Column-II
(a) Ciliated bronchioles (i) Female reproductive tract
(b) Fallopian tubes (ii) Lungs
(c) Eustachian tube (iii) Ear
Chapter: Sexual Reproduction in Flowering Plants
Topic: Post-fertilisation Structures and Events
Subtopic: Endosperm Development
Keywords:
Coconut water – The free nuclear liquid endosperm of a tender coconut.
Endosperm – Nutritive tissue formed after double fertilisation, nourishing the developing embryo.
Free nuclear endosperm – Type of endosperm where repeated nuclear divisions occur without cell wall formation.
Proembryo – Early stage of embryo before differentiation.
Embryo sac – Female gametophyte in angiosperms where fertilisation occurs.
Mesocarp – Middle fleshy layer of fruit wall.
Endocarp – Innermost hard layer of fruit wall.
Double fertilisation – Unique feature of angiosperms where one male gamete fuses with egg and the other with polar nuclei.
Nuclear divisions – Process of multiplication of nuclei without cytokinesis, seen in free nuclear endosperm.
Clinical relevance – Endosperm is a major source of nutrition in cereals consumed by humans.
Lead Question – 2016 (Phase 1)
The coconut water from tender coconut represents:
(1) Endocarp
(2) Fleshy mesocarp
(3) Free nuclear proembryo
(4) Free nuclear endosperm
Explanation: Coconut water is the free nuclear endosperm formed after fertilisation by the fusion of a male gamete with polar nuclei. It remains multinucleate and provides nutrition to the developing embryo. The coconut’s white kernel is the cellular endosperm. Answer: (4) Free nuclear endosperm.
Question 2. The white kernel (flesh) of coconut represents:
(1) Free nuclear proembryo
(2) Cellular endosperm
(3) Fleshy mesocarp
(4) Embryo
Explanation: The edible white kernel of coconut is the cellular endosperm, formed when free nuclear endosperm undergoes cytokinesis. It stores food for the developing embryo. Answer: (2) Cellular endosperm.
Question 3. Which type of endosperm development occurs in coconut?
(1) Nuclear
(2) Cellular
(3) Helobial
(4) None of the above
Explanation: Coconut shows nuclear type of endosperm development where free nuclear divisions occur initially, and later cell wall formation produces cellular endosperm (white kernel). Answer: (1) Nuclear.
Question 4. Assertion (A): Coconut water is free nuclear endosperm.
Reason (R): It results from fusion of male gamete with secondary nucleus during double fertilisation.
(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
(3) A is true but R is false
(4) A is false but R is true
Explanation: The second fertilisation event fuses a male gamete with two polar nuclei, forming primary endosperm nucleus, which undergoes nuclear divisions to form coconut water. Thus, A and R are true and R correctly explains A. Answer: (1).
Question 5. Match the following:
A. Coconut water → (i) Free nuclear endosperm
B. Coconut flesh → (ii) Cellular endosperm
C. Endocarp → (iii) Hard shell
D. Mesocarp → (iv) Fibrous husk
(1) A-i, B-ii, C-iii, D-iv
(2) A-ii, B-i, C-iv, D-iii
(3) A-iii, B-iv, C-i, D-ii
(4) A-iv, B-iii, C-ii, D-i
Explanation: Coconut water is free nuclear endosperm, white flesh is cellular endosperm, endocarp forms the hard shell, and mesocarp is the fibrous husk. Answer: (1).
Question 6. The nutritive tissue for developing embryo in angiosperms is:
(1) Endosperm
(2) Perisperm
(3) Mesocarp
(4) Cotyledon
Explanation: Endosperm is the unique nutritive tissue of angiosperms formed by triple fusion during double fertilisation. It provides nutrition to the developing embryo and may persist or get absorbed. Answer: (1) Endosperm.
Question 7. Fill in the blank: The fusion of one male gamete with two polar nuclei forms ________.
(1) Primary endosperm nucleus
(2) Secondary nucleus
(3) Syngamy
(4) Zygote
Explanation: The fusion of a male gamete with two polar nuclei inside the central cell produces the triploid primary endosperm nucleus, which develops into endosperm. Answer: (1) Primary endosperm nucleus.
Question 8. A farmer observed that in cereals like rice and wheat, the seed is rich in starchy endosperm. This tissue is homologous to which part in coconut?
(1) Endocarp
(2) Free nuclear endosperm
(3) Mesocarp
(4) Cotyledon
Explanation: Starchy endosperm in cereals is homologous to coconut endosperm. In tender coconut, it is free nuclear (liquid) and later forms the white kernel (cellular). Answer: (2) Free nuclear endosperm.
Question 9. Passage-based MCQ:
"In flowering plants, double fertilisation produces both zygote and primary endosperm nucleus. The primary endosperm nucleus undergoes divisions forming free nuclear endosperm. In coconut, this is represented by liquid endosperm (coconut water), which nourishes the embryo until maturity."
Which statement is correct?
(1) Coconut water is mesocarp
(2) Coconut water is free nuclear endosperm
(3) Coconut flesh is free nuclear endosperm
(4) Coconut water is zygote
Explanation: Coconut water is the liquid free nuclear endosperm formed by nuclear divisions without cytokinesis. Coconut flesh is the cellular endosperm. Answer: (2) Coconut water is free nuclear endosperm.
Question 10. In clinical nutrition, why are cereals like rice and maize considered staple foods?
(1) They are rich in endosperm providing carbohydrates
(2) They are rich in proteins from embryo
(3) They are rich in vitamins from pericarp
(4) They contain high water content like coconut
Explanation: Cereals provide staple diet because their seeds contain large amounts of starchy endosperm that supply carbohydrates as the main energy source. This is comparable to nutritive role of endosperm in coconut. Answer: (1) They are rich in endosperm providing carbohydrates.