Chapter: Cardiovascular System; Topic: Venous Drainage of Heart; Subtopic: Sinus Venarum and Cardiac Veins
Keyword Definitions:
• Sinus venarum: Smooth posterior part of right atrium where veins open.
• Coronary sinus: A large venous channel that collects blood from cardiac veins.
• Anterior cardiac veins: Veins draining right ventricle directly into right atrium.
• Small cardiac vein: Vein accompanying the right marginal artery to coronary sinus.
Lead Question (2015):
All veins open in sinus venarum except -
a) SVC
b) Coronary sinus
c) Anterior cardiac vein
d) Small cardiac vein
Explanation: The anterior cardiac veins are the only veins that open directly into the right atrium, not into the sinus venarum. The superior vena cava, inferior vena cava, and coronary sinus all drain into the smooth-walled sinus venarum. This distinction is important in understanding venous return of the heart. Answer: c) Anterior cardiac vein.
1) Which vein opens directly into the right atrium apart from the venae cavae?
a) Coronary sinus
b) Anterior cardiac vein
c) Small cardiac vein
d) Middle cardiac vein
Explanation: The anterior cardiac veins directly drain blood from the right ventricle into the right atrium, bypassing the coronary sinus. This unique drainage differentiates them from other cardiac veins which open into the coronary sinus. Answer: b) Anterior cardiac vein.
2) The coronary sinus opens into which chamber of the heart?
a) Left atrium
b) Right atrium
c) Right ventricle
d) Left ventricle
Explanation: The coronary sinus opens into the posterior wall of the right atrium, close to the opening of the inferior vena cava. It collects blood from the great, middle, and small cardiac veins, serving as the main venous channel of the heart. Answer: b) Right atrium.
3) The small cardiac vein accompanies which artery?
a) Right marginal artery
b) Left marginal artery
c) Anterior interventricular artery
d) Posterior interventricular artery
Explanation: The small cardiac vein runs along the right margin of the heart with the right marginal artery. It drains the right atrium and ventricle and empties into the coronary sinus. This relationship is clinically useful in coronary imaging. Answer: a) Right marginal artery.
4) The great cardiac vein runs along which groove?
a) Coronary groove
b) Posterior interventricular groove
c) Anterior interventricular groove
d) Atrioventricular groove
Explanation: The great cardiac vein runs in the anterior interventricular groove alongside the left anterior descending artery. It collects blood from the anterior surfaces of the ventricles and joins the coronary sinus posteriorly. Answer: c) Anterior interventricular groove.
5) Which of the following veins does not drain into the coronary sinus?
a) Middle cardiac vein
b) Small cardiac vein
c) Great cardiac vein
d) Anterior cardiac vein
Explanation: The anterior cardiac veins bypass the coronary sinus and drain directly into the right atrium. All other cardiac veins empty into the coronary sinus before reaching the right atrium. Answer: d) Anterior cardiac vein.
6) A patient undergoing cardiac catheterization shows blockage of the coronary sinus. Which veins are likely to remain unaffected?
a) Great cardiac veins
b) Middle cardiac veins
c) Anterior cardiac veins
d) Small cardiac veins
Explanation: The anterior cardiac veins drain directly into the right atrium and are therefore unaffected by coronary sinus obstruction. Other cardiac veins empty into the coronary sinus and would be impacted. Answer: c) Anterior cardiac veins.
7) The Thebesian veins drain into which cardiac chamber?
a) Right atrium and left atrium
b) Only right atrium
c) Only left atrium
d) Left ventricle
Explanation: Thebesian veins are small veins that drain directly into all chambers of the heart, especially the right atrium and ventricle. They help in venous return of myocardial blood without entering major veins. Answer: a) Right atrium and left atrium.
8) Which structure marks the junction between the sinus venarum and the right atrial appendage?
a) Crista terminalis
b) Fossa ovalis
c) Pectinate muscles
d) Sulcus limitans
Explanation: The crista terminalis is a ridge that separates the smooth posterior sinus venarum from the rough pectinate muscle-covered anterior wall of the right atrium. It is an important landmark in right atrial anatomy. Answer: a) Crista terminalis.
9) The coronary sinus receives blood from all except:
a) Great cardiac vein
b) Middle cardiac vein
c) Small cardiac vein
d) Anterior cardiac vein
Explanation: The anterior cardiac veins drain the right ventricle directly into the right atrium, bypassing the coronary sinus. All other named cardiac veins join the coronary sinus. Answer: d) Anterior cardiac vein.
10) During cardiac surgery, which vein serves as a guide to locate the coronary sinus?
a) Middle cardiac vein
b) Great cardiac vein
c) Small cardiac vein
d) Oblique vein of left atrium
Explanation: The oblique vein of the left atrium is a small vein that joins the coronary sinus at its upper end, serving as a landmark during surgery. It marks the terminal portion of the left atrium and is important in anatomical orientation. Answer: d) Oblique vein of left atrium.
Chapter: Cardiovascular System; Topic: Coronary Circulation; Subtopic: Atrioventricular (Coronary) Groove
Keyword Definitions:
• Atrioventricular groove: A groove between atria and ventricles that lodges major coronary vessels.
• Right coronary artery (RCA): Runs in the right part of the atrioventricular groove supplying the right heart.
• Circumflex artery: A branch of left coronary artery running in the left atrioventricular groove.
• Left anterior descending artery (LAD): Descends in the anterior interventricular groove, not the atrioventricular groove.
Lead Question (2015):
True about atrioventricular groove are all except ?
a) Contains left anterior descending coronary artery
b) Also called coronary sulcus
c) Contains right coronary artery
d) Contains circumflex branch of left coronary artery
Explanation: The left anterior descending artery runs in the anterior interventricular groove, not in the atrioventricular groove. The right coronary and circumflex arteries lie in the atrioventricular (coronary) sulcus, which separates atria from ventricles. Thus, option (a) is incorrect. Answer: a) Contains left anterior descending coronary artery.
1) The atrioventricular groove separates which two parts of the heart?
a) Right and left ventricles
b) Atria and ventricles
c) Right and left atria
d) Left atrium and aorta
Explanation: The atrioventricular groove marks the boundary between atria and ventricles and houses the major coronary arteries and coronary sinus. It encircles the heart transversely and is visible on both anterior and posterior surfaces. Answer: b) Atria and ventricles.
2) Which artery lies in the anterior interventricular groove?
a) Circumflex artery
b) Left anterior descending artery
c) Right coronary artery
d) Posterior descending artery
Explanation: The left anterior descending (LAD) artery, a branch of the left coronary artery, runs in the anterior interventricular groove. It supplies the anterior wall, septum, and apex of the heart. LAD blockage often causes severe myocardial infarction. Answer: b) Left anterior descending artery.
3) The coronary sinus lies in which groove?
a) Interventricular groove
b) Atrioventricular groove
c) Aortic groove
d) Pulmonary groove
Explanation: The coronary sinus lies in the posterior part of the atrioventricular groove. It collects blood from cardiac veins and opens into the right atrium. Its location is clinically important in cardiac catheterization and pacemaker implantation. Answer: b) Atrioventricular groove.
4) The circumflex artery supplies all of the following except:
a) Left atrium
b) Left ventricle
c) Right atrium
d) Part of interventricular septum
Explanation: The circumflex artery supplies the left atrium and left ventricle but not the right atrium. It runs in the left part of the atrioventricular groove and anastomoses with the right coronary artery posteriorly. Answer: c) Right atrium.
5) Which structure is related to the right atrioventricular groove?
a) Great cardiac vein
b) Middle cardiac vein
c) Small cardiac vein
d) Anterior cardiac veins
Explanation: The small cardiac vein runs along the right atrioventricular groove with the right coronary artery and drains into the coronary sinus. This relationship helps in identifying the right coronary course during surgeries. Answer: c) Small cardiac vein.
6) A patient with blockage in the right coronary artery may experience ischemia in which part of the heart?
a) Left atrium
b) Right atrium and ventricle
c) Interventricular septum only
d) Apex of heart
Explanation: The right coronary artery supplies the right atrium, right ventricle, and often part of the interventricular septum. Its occlusion may cause conduction abnormalities due to involvement of the SA or AV node. Answer: b) Right atrium and ventricle.
7) During coronary angiography, a blockage is seen in the left circumflex artery. Which region of the heart is likely affected?
a) Right atrium
b) Left atrium and posterior left ventricle
c) Anterior interventricular septum
d) Right ventricle
Explanation: The left circumflex artery supplies the left atrium and the posterior part of the left ventricle. Blockage leads to ischemia in these regions and may cause arrhythmias or left-sided heart failure. Answer: b) Left atrium and posterior left ventricle.
8) The coronary sulcus is also known as:
a) Atrioventricular groove
b) Interventricular groove
c) Coronary sinus
d) Transverse sinus
Explanation: The coronary sulcus is another name for the atrioventricular groove. It encircles the heart and separates the atria from the ventricles, containing major coronary vessels. Answer: a) Atrioventricular groove.
9) Which artery supplies the posterior part of the interventricular septum in right-dominant circulation?
a) Left anterior descending artery
b) Posterior descending artery (from RCA)
c) Circumflex artery
d) Marginal artery
Explanation: In right-dominant circulation, the posterior descending artery arises from the right coronary artery and supplies the posterior third of the interventricular septum. This pattern is present in about 70% of individuals. Answer: b) Posterior descending artery (from RCA).
10) During bypass surgery, which artery is used as a graft to replace the blocked LAD artery?
a) Right coronary artery
b) Left internal mammary artery
c) Subclavian artery
d) Inferior phrenic artery
Explanation: The left internal mammary artery (LIMA) is commonly used for coronary artery bypass grafting, especially for the LAD artery, due to its durability and long-term patency. It provides excellent blood flow to the anterior heart wall. Answer: b) Left internal mammary artery.
Chapter: Cardiovascular System; Topic: Coronary Circulation; Subtopic: Cardiac Veins and Venous Drainage of Heart
Keyword Definitions:
• Great cardiac vein: Drains the anterior surface of the heart and runs with the LAD artery.
• Middle cardiac vein: Drains the posterior surface of the ventricles and runs with the posterior interventricular artery.
• Coronary sinus: Main venous channel that collects blood from cardiac veins and opens into the right atrium.
• Anterior cardiac veins: Drain the anterior surface of the right ventricle directly into the right atrium.
Lead Question (2015):
Which vein is found at the apex of the heart?
a) Great cardiac vein
b) Coronary sinus
c) Anterior cardiac vein
d) Middle cardiac vein
Explanation: The great cardiac vein begins at the apex of the heart and ascends in the anterior interventricular groove with the LAD artery. It drains the anterior surface of the left ventricle and later joins the coronary sinus. Other veins begin on the posterior or right surfaces. Answer: a) Great cardiac vein.
1) Which vein accompanies the posterior interventricular artery?
a) Great cardiac vein
b) Middle cardiac vein
c) Small cardiac vein
d) Anterior cardiac vein
Explanation: The middle cardiac vein accompanies the posterior interventricular artery in the posterior interventricular groove. It drains the posterior part of both ventricles and empties into the coronary sinus. This pairing helps in identifying vessels during cardiac surgery. Answer: b) Middle cardiac vein.
2) Which vein drains the right ventricle directly into the right atrium?
a) Great cardiac vein
b) Anterior cardiac vein
c) Middle cardiac vein
d) Coronary sinus
Explanation: The anterior cardiac veins are small veins on the anterior wall of the right ventricle that drain directly into the right atrium. Unlike other cardiac veins, they do not open into the coronary sinus. Answer: b) Anterior cardiac vein.
3) The coronary sinus opens into which chamber of the heart?
a) Left atrium
b) Right atrium
c) Left ventricle
d) Right ventricle
Explanation: The coronary sinus opens into the right atrium, between the inferior vena cava and tricuspid valve. It returns deoxygenated blood from most of the myocardium except anterior cardiac veins. Answer: b) Right atrium.
4) Which structure marks the beginning of the coronary sinus?
a) Great cardiac vein
b) Small cardiac vein
c) Middle cardiac vein
d) Oblique vein of left atrium
Explanation: The oblique vein of the left atrium joins the great cardiac vein to form the coronary sinus. This structure runs on the posterior surface of the heart in the atrioventricular groove. Answer: d) Oblique vein of left atrium.
5) A 60-year-old male undergoing cardiac catheterization shows blockage in the LAD artery. Which vein runs parallel to it and may assist in diagnosis?
a) Great cardiac vein
b) Middle cardiac vein
c) Small cardiac vein
d) Posterior vein of left ventricle
Explanation: The great cardiac vein runs parallel to the LAD artery in the anterior interventricular groove. It reflects perfusion status of the anterior myocardium and helps in venography. Answer: a) Great cardiac vein.
6) The coronary sinus receives blood from all of the following except:
a) Great cardiac vein
b) Middle cardiac vein
c) Anterior cardiac vein
d) Small cardiac vein
Explanation: The anterior cardiac veins do not drain into the coronary sinus. They directly open into the right atrium. All other major veins empty into the coronary sinus, which then drains into the right atrium. Answer: c) Anterior cardiac vein.
7) The smallest cardiac veins (Thebesian veins) open into:
a) Coronary sinus
b) Right atrium only
c) All chambers of the heart
d) Left atrium only
Explanation: The Thebesian veins are small veins that open directly into all four heart chambers, mainly the right atrium and right ventricle. They provide a minimal alternate venous drainage route. Answer: c) All chambers of the heart.
8) During surgery, the coronary sinus was identified in the posterior atrioventricular groove. It lies closest to which heart valve?
a) Tricuspid valve
b) Pulmonary valve
c) Mitral valve
d) Aortic valve
Explanation: The coronary sinus opens into the right atrium near the orifice of the tricuspid valve. This proximity is important during pacemaker or catheter placements. Answer: a) Tricuspid valve.
9) The small cardiac vein usually accompanies which artery?
a) Right marginal artery
b) Posterior descending artery
c) Circumflex artery
d) LAD artery
Explanation: The small cardiac vein runs with the right marginal artery along the inferior border of the heart and empties into the coronary sinus. This vein drains the right atrium and ventricle. Answer: a) Right marginal artery.
10) During coronary venography, dye injected into the coronary sinus spreads into which major tributaries?
a) Great, middle, and small cardiac veins
b) Only great cardiac vein
c) Only anterior cardiac veins
d) Thebesian veins
Explanation: The coronary sinus receives blood from the great, middle, and small cardiac veins, which are its main tributaries. These veins are visualized during venography, helping assess myocardial venous drainage. Answer: a) Great, middle, and small cardiac veins.
Chapter: Cardiovascular System; Topic: Venous Drainage of the Heart; Subtopic: Veins Opening into the Right Atrium
Keyword Definitions:
• Right Atrium: The right upper chamber of the heart that receives deoxygenated blood from systemic circulation.
• Coronary Sinus: A large venous channel on the posterior surface of the heart that collects blood from most cardiac veins.
• Anterior Cardiac Veins: Small veins draining the anterior wall of the right ventricle directly into the right atrium.
• Thebesian Veins: Small veins draining myocardium directly into cardiac chambers.
• Great Cardiac Vein: Main tributary of the coronary sinus that drains the anterior interventricular region.
Lead Question - 2015
Which of the following does not directly drain into right atrium?
a) Great cardiac vein
b) Anterior cardiac vein
c) Thebesian vein
d) Venae cordis minimi
Explanation: The correct answer is a) Great cardiac vein. The great cardiac vein drains the anterior interventricular region and opens into the coronary sinus, not directly into the right atrium. In contrast, anterior cardiac and Thebesian veins directly drain into the right atrium. Understanding venous return helps in cardiac surgeries and diagnostics.
1. Which of the following veins drains directly into the coronary sinus?
a) Middle cardiac vein
b) Anterior cardiac vein
c) Thebesian vein
d) Venae cordis minimae
Explanation: The correct answer is a) Middle cardiac vein. It runs in the posterior interventricular groove and drains into the coronary sinus, which empties into the right atrium, forming the main venous return from the posterior side of the heart.
2. The coronary sinus opens into which chamber of the heart?
a) Right atrium
b) Right ventricle
c) Left atrium
d) Left ventricle
Explanation: The correct answer is a) Right atrium. The coronary sinus is the main venous drainage channel of the heart that collects blood from the cardiac veins and empties into the right atrium near the opening of the inferior vena cava.
3. The great cardiac vein accompanies which artery?
a) Left anterior descending artery
b) Circumflex artery
c) Right coronary artery
d) Posterior descending artery
Explanation: The correct answer is a) Left anterior descending artery. The great cardiac vein runs alongside the LAD in the anterior interventricular sulcus, collecting blood from the anterior portion of the heart and draining into the coronary sinus.
4. The Thebesian veins drain directly into:
a) Right atrium only
b) All four chambers
c) Left atrium only
d) Coronary sinus
Explanation: The correct answer is b) All four chambers. The Thebesian veins are small veins of the myocardium that drain directly into all four heart chambers, though most are found in the right atrium and right ventricle.
5. Which of the following veins drain the anterior wall of the right ventricle?
a) Anterior cardiac veins
b) Middle cardiac vein
c) Small cardiac vein
d) Great cardiac vein
Explanation: The correct answer is a) Anterior cardiac veins. These veins run on the anterior surface of the right ventricle and drain directly into the right atrium without joining the coronary sinus.
6. A patient with obstruction of the coronary sinus will have impaired drainage from:
a) Middle and great cardiac veins
b) Anterior cardiac veins
c) Thebesian veins
d) Right marginal veins only
Explanation: The correct answer is a) Middle and great cardiac veins. These major veins drain into the coronary sinus, so obstruction leads to venous congestion and impaired myocardial venous return.
7. During cardiac catheterization, dye injected into the coronary sinus will reach which chamber first?
a) Right atrium
b) Left atrium
c) Right ventricle
d) Left ventricle
Explanation: The correct answer is a) Right atrium. The coronary sinus opens into the posterior wall of the right atrium, allowing venous blood and contrast to flow directly into it during imaging.
8. In cardiac transplantation, anastomosis of the donor’s right atrium involves which structure of venous drainage?
a) Coronary sinus
b) Pulmonary veins
c) Thebesian veins
d) Anterior cardiac veins
Explanation: The correct answer is a) Coronary sinus. The coronary sinus forms part of the posterior right atrial wall; during transplantation, its continuity with the donor atrium ensures proper venous return from the myocardium.
9. The small cardiac vein runs along which artery?
a) Right coronary artery
b) Left anterior descending artery
c) Circumflex artery
d) Posterior descending artery
Explanation: The correct answer is a) Right coronary artery. The small cardiac vein accompanies the right coronary artery in the coronary sulcus and drains the right atrium and ventricle into the coronary sinus.
10. Clinically, enlargement of the coronary sinus may indicate increased pressure in:
a) Right atrium
b) Left ventricle
c) Pulmonary artery
d) Aorta
Explanation: The correct answer is a) Right atrium. Since the coronary sinus opens into the right atrium, elevated right atrial pressure causes venous engorgement, which can be visualized on imaging and indicates cardiac dysfunction.
Chapter: Cardiovascular System; Topic: Venous Drainage of Heart; Subtopic: Coronary Sinus and Its Tributaries
Keyword Definitions:
• Coronary Sinus: A large venous channel on the posterior surface of the heart that drains blood from most cardiac veins into the right atrium.
• Great Cardiac Vein: The main tributary of the coronary sinus that runs in the anterior interventricular sulcus.
• Small Cardiac Vein: Runs along the right margin of the heart and drains into the coronary sinus.
• Middle Cardiac Vein: Lies in the posterior interventricular sulcus and empties into the coronary sinus.
• Thebesian Veins: Tiny veins that drain directly into cardiac chambers, not through the coronary sinus.
Lead Question - 2015
Tributary of coronary sinus?
a) Anterior cardiac vein
b) Thebesian vein
c) Smallest cardiac vein
d) Great cardiac vein
Explanation: The correct answer is d) Great cardiac vein. The coronary sinus receives venous blood from the great, middle, and small cardiac veins. The great cardiac vein accompanies the left anterior descending artery in the anterior interventricular groove and drains into the coronary sinus, which then opens into the right atrium, completing myocardial venous return.
1. Which of the following veins directly drains into the coronary sinus?
a) Middle cardiac vein
b) Anterior cardiac vein
c) Thebesian vein
d) Pulmonary vein
Explanation: The correct answer is a) Middle cardiac vein. This vein runs in the posterior interventricular groove, draining the posterior walls of both ventricles and directly joining the coronary sinus. It is a key component of the venous drainage of the myocardium.
2. The coronary sinus opens into which chamber of the heart?
a) Right atrium
b) Right ventricle
c) Left atrium
d) Left ventricle
Explanation: The correct answer is a) Right atrium. The coronary sinus opens into the right atrium near the opening of the inferior vena cava, allowing deoxygenated blood from the myocardium to return to the venous circulation.
3. Which vein runs parallel to the posterior descending artery?
a) Middle cardiac vein
b) Small cardiac vein
c) Great cardiac vein
d) Anterior cardiac vein
Explanation: The correct answer is a) Middle cardiac vein. It accompanies the posterior descending artery in the posterior interventricular groove, draining venous blood from the posterior parts of both ventricles into the coronary sinus.
4. Which of the following veins bypasses the coronary sinus and drains directly into the right atrium?
a) Anterior cardiac veins
b) Small cardiac vein
c) Middle cardiac vein
d) Great cardiac vein
Explanation: The correct answer is a) Anterior cardiac veins. These veins drain the anterior surface of the right ventricle directly into the right atrium without joining the coronary sinus, distinguishing them from other cardiac veins.
5. Which of the following is not a tributary of the coronary sinus?
a) Great cardiac vein
b) Middle cardiac vein
c) Anterior cardiac vein
d) Small cardiac vein
Explanation: The correct answer is c) Anterior cardiac vein. The anterior cardiac veins open directly into the right atrium, while the great, middle, and small cardiac veins drain into the coronary sinus, which then empties into the right atrium.
6. During angiography, dye injected into the coronary sinus will appear in which cardiac chamber first?
a) Right atrium
b) Left atrium
c) Right ventricle
d) Pulmonary trunk
Explanation: The correct answer is a) Right atrium. The coronary sinus opens into the right atrium’s posterior wall, so contrast dye injected during imaging will appear in this chamber first, confirming venous drainage.
7. Which cardiac vein accompanies the right coronary artery in the coronary sulcus?
a) Small cardiac vein
b) Middle cardiac vein
c) Great cardiac vein
d) Anterior cardiac vein
Explanation: The correct answer is a) Small cardiac vein. This vein runs along the right coronary artery and drains the right atrium and ventricle, ultimately opening into the coronary sinus posteriorly.
8. Enlargement of the coronary sinus on echocardiography suggests increased pressure in which chamber?
a) Right atrium
b) Left ventricle
c) Left atrium
d) Right ventricle
Explanation: The correct answer is a) Right atrium. Since the coronary sinus empties into the right atrium, elevated right atrial pressure leads to its dilation, which is often seen in tricuspid valve disease or pulmonary hypertension.
9. In cardiac transplantation, continuity of venous return is maintained by connecting which structure?
a) Coronary sinus
b) Pulmonary veins
c) Thebesian veins
d) Anterior cardiac veins
Explanation: The correct answer is a) Coronary sinus. During heart transplantation, the coronary sinus is preserved to ensure the venous return from the myocardium is directed into the donor’s right atrium.
10. A patient with thrombosis of the coronary sinus may present with which clinical finding?
a) Myocardial congestion and pain
b) Left ventricular hypertrophy
c) Pulmonary embolism
d) Systemic hypertension
Explanation: The correct answer is a) Myocardial congestion and pain. Obstruction of the coronary sinus impairs venous drainage of the heart, leading to myocardial congestion, ischemic pain, and possible arrhythmias due to increased venous pressure within the cardiac tissue.
Chapter: Respiratory System; Topic: Anatomy of Lungs; Subtopic: Segments of Right Lung
Keyword Definitions:
• Bronchopulmonary Segment: A pyramid-shaped portion of the lung supplied by a segmental bronchus and a branch of the pulmonary artery.
• Right Lung: It has three lobes—upper, middle, and lower—divided by oblique and horizontal fissures.
• Upper Lobe Segments: Apical, posterior, and anterior segments.
• Middle Lobe Segments: Medial and lateral segments.
• Lower Lobe Segments: Superior, anterior basal, posterior basal, medial basal, and lateral basal.
Lead Question - 2015
Which are segments of upper lobe of right lung?
a) Anterior, posterior, media
b) Lateral, medial, superior
c) Apical, anterior, posterior
d) Basal, medial, lateral
Explanation: The correct answer is c) Apical, anterior, posterior. The upper lobe of the right lung is divided into three bronchopulmonary segments: apical, posterior, and anterior. Each segment has its own bronchial and vascular supply, separated by connective tissue septa, allowing independent infection or collapse. These segments are crucial in segmental lung resections and clinical localization of lesions.
1. How many bronchopulmonary segments are present in the right lung?
a) 7
b) 8
c) 9
d) 10
Explanation: The correct answer is d) 10. The right lung has 10 bronchopulmonary segments—3 in the upper lobe, 2 in the middle lobe, and 5 in the lower lobe. Each is functionally and anatomically independent, which is significant during segmentectomy procedures in thoracic surgery.
2. Which bronchopulmonary segment of the right lung is most likely to receive aspirated foreign bodies in an upright person?
a) Apical
b) Posterior basal
c) Superior
d) Medial basal
Explanation: The correct answer is b) Posterior basal. Due to the vertical alignment of the right main bronchus, foreign bodies tend to lodge in the lower lobe, particularly in the posterior basal segment, which is dependent when upright, predisposing it to aspiration pneumonia.
3. The middle lobe of the right lung is separated from the upper lobe by which fissure?
a) Oblique fissure
b) Horizontal fissure
c) Both fissures
d) Cardiac notch
Explanation: The correct answer is b) Horizontal fissure. The horizontal fissure divides the upper and middle lobes of the right lung, extending from the oblique fissure to the anterior border at the 4th costal cartilage level.
4. During bronchoscopy, which bronchus is more vertically oriented and wider?
a) Left main bronchus
b) Right main bronchus
c) Both are equal
d) Segmental bronchus
Explanation: The correct answer is b) Right main bronchus. It is shorter, wider, and more vertical than the left, making it a common site for aspiration and foreign body lodgment. This anatomical feature is important during intubation and bronchoscopy.
5. Which lobe of the right lung contains the medial and lateral segments?
a) Upper lobe
b) Middle lobe
c) Lower lobe
d) Accessory lobe
Explanation: The correct answer is b) Middle lobe. The right middle lobe comprises medial and lateral bronchopulmonary segments, supplied by the middle lobe bronchus. This lobe is prone to recurrent infections and collapse due to its narrow bronchus and dependent position.
6. A lesion in the anterior segment of the right upper lobe would most likely be seen in which chest X-ray view?
a) Lateral view
b) PA view
c) Oblique view
d) Lateral decubitus view
Explanation: The correct answer is a) Lateral view. The anterior segment lies in front of the oblique fissure and is best visualized on a lateral chest X-ray, where its pathology can be differentiated from middle lobe or lingular lesions.
7. The lingula of the left lung corresponds to which lobe of the right lung anatomically?
a) Upper lobe
b) Middle lobe
c) Lower lobe
d) Both upper and middle
Explanation: The correct answer is b) Middle lobe. The lingula is part of the left upper lobe but functionally equivalent to the middle lobe of the right lung. It consists of superior and inferior segments and lies adjacent to the cardiac notch.
8. Which segment of the right lower lobe is most dependent in the supine position?
a) Posterior basal
b) Superior
c) Medial basal
d) Anterior basal
Explanation: The correct answer is a) Posterior basal. In the supine position, this segment is dependent, predisposing it to aspiration or fluid accumulation in bedridden patients, a key point in managing pneumonia.
9. Which lung is smaller and why?
a) Left lung, due to cardiac impression
b) Right lung, due to liver position
c) Left lung, due to higher diaphragm
d) Right lung, due to mediastinal shift
Explanation: The correct answer is a) Left lung. The left lung is smaller as it accommodates the cardiac notch and forms the cardiac impression for the heart, containing only two lobes compared to three on the right side.
10. During lobectomy, which structure is removed along with each lobe?
a) Segmental bronchus
b) Bronchial artery
c) Pulmonary vein
d) All of the above
Explanation: The correct answer is d) All of the above. Each lobe has distinct bronchial, arterial, and venous supply. Lobectomy involves removal of these along with the lobe. Understanding segmental anatomy ensures precise excision and preservation of remaining lung function.
Chapter: Thorax; Topic: Lungs and Pleura; Subtopic: Hilum of the Lung
Keyword Definitions:
• Hilum of lung: The area on the mediastinal surface where bronchi, blood vessels, lymphatics, and nerves enter or leave the lung.
• Pulmonary artery: Carries deoxygenated blood from the right ventricle to the lungs.
• Pulmonary veins: Carry oxygenated blood from lungs to left atrium.
• Bronchial artery: Provides oxygenated blood to lung tissue.
• Main bronchus: Primary airway entering each lung.
Lead Question - 2015
What is the uppermost structure in left lung hilum?
a) Pulmonary artery
b) Pulmonary vein
c) Bronchial artery
d) Left mainstem bronchus
Explanation: The pulmonary artery is the uppermost structure in the hilum of the left lung, lying superior to the bronchus and veins. The arrangement in the left lung hilum from above downward is pulmonary artery, bronchus, and pulmonary veins. This differs from the right lung, where the bronchus lies above the artery. Hence, the correct answer is a) Pulmonary artery.
1. Which structure lies lowest in the hilum of the left lung?
a) Pulmonary artery
b) Pulmonary vein
c) Bronchus
d) Lymph node
Explanation: The pulmonary veins occupy the lowest position in the left lung hilum. The typical order from superior to inferior is pulmonary artery, bronchus, and pulmonary veins. This anatomical arrangement is significant during surgical procedures and radiological identification. Hence, the correct answer is b) Pulmonary vein.
2. In the right lung, the bronchus lies:
a) Above the pulmonary artery
b) Below the pulmonary artery
c) Anterior to the pulmonary artery
d) Posterior to the pulmonary veins
Explanation: In the right lung, the bronchus lies above the pulmonary artery, which gives rise to the term “eparterial bronchus.” The arrangement in the right lung hilum is bronchus above, pulmonary artery in the middle, and pulmonary veins below. Hence, the correct answer is a) Above the pulmonary artery.
3. Which structure passes posterior to the root of the lung?
a) Phrenic nerve
b) Pulmonary veins
c) Vagus nerve
d) Internal thoracic artery
Explanation: The vagus nerve passes posterior to the root of the lung, while the phrenic nerve passes anteriorly. This relationship is important in thoracic surgeries to prevent nerve injury during dissection around the lung root. Hence, the correct answer is c) Vagus nerve.
4. Clinical case: During lobectomy, a surgeon identifies a structure lying superior in the left lung hilum. Which is it?
a) Pulmonary artery
b) Pulmonary vein
c) Bronchus
d) Lymph node
Explanation: The pulmonary artery lies superior in the left lung hilum, making it the structure encountered first during dissection from above. This helps surgeons identify and ligate vessels correctly. Hence, the correct answer is a) Pulmonary artery.
5. Which structure forms the most posterior relation of the hilum of the lung?
a) Pulmonary vein
b) Pulmonary artery
c) Bronchus
d) Phrenic nerve
Explanation: The bronchus forms the most posterior relation of the hilum. It lies behind the pulmonary vessels and is the last structure seen from an anterior approach. This relationship is crucial in radiology and surgical anatomy. Hence, the correct answer is c) Bronchus.
6. In bronchogenic carcinoma of the left upper lobe, which hilum structure is most likely compressed first?
a) Pulmonary vein
b) Pulmonary artery
c) Left bronchus
d) Lymph node
Explanation: The pulmonary artery is most likely to be compressed first due to its superior position in the left hilum. Enlarged lymph nodes or tumors in the upper lobe can impinge on the artery, affecting blood flow to the lung. Hence, the correct answer is b) Pulmonary artery.
7. The root of the lung includes all except:
a) Pulmonary artery
b) Pulmonary vein
c) Bronchial artery
d) Phrenic nerve
Explanation: The phrenic nerve does not form part of the lung root; it passes anterior to it. The root includes pulmonary arteries, veins, bronchi, bronchial arteries, nerves, and lymphatics enclosed by pleura. Hence, the correct answer is d) Phrenic nerve.
8. Clinical case: A CT scan shows a mass compressing the structure posterior to the right lung hilum. Which nerve is likely affected?
a) Vagus nerve
b) Phrenic nerve
c) Intercostal nerve
d) Sympathetic trunk
Explanation: The vagus nerve passes posterior to the lung hilum, so a posteriorly placed mass could compress it, leading to symptoms like hoarseness due to recurrent laryngeal involvement. Hence, the correct answer is a) Vagus nerve.
9. The hilum of the right lung contains how many pulmonary veins?
a) One
b) Two
c) Three
d) Four
Explanation: The right lung hilum contains two pulmonary veins — superior and inferior — which carry oxygenated blood to the left atrium. They lie anterior and inferior to the bronchus and artery. Hence, the correct answer is b) Two.
10. Which structure lies anterior to the root of the lung?
a) Vagus nerve
b) Pulmonary artery
c) Phrenic nerve
d) Bronchus
Explanation: The phrenic nerve lies anterior to the root of the lung, running between pleura and pericardium. It supplies the diaphragm and is important to identify in surgeries to prevent paralysis. Hence, the correct answer is c) Phrenic nerve.
Chapter: Pelvis; Topic: Female Reproductive System; Subtopic: Lymphatic Drainage of Ovary
Keyword Definitions:
• Ovary: Female gonad producing ova and hormones (estrogen, progesterone).
• Lymphatic drainage: Flow of lymph from organs to lymph nodes through defined vessels.
• Paraaortic lymph nodes: Nodes located along the abdominal aorta receiving drainage from ovaries, kidneys, and uterus.
• Inguinal lymph nodes: Nodes in the groin area draining perineum and external genitalia.
• Obturator lymph nodes: Nodes near obturator vessels draining pelvic viscera.
Lead Question - 2015
Lymphatic drainage of ovary?
a) Deep inguinal
b) Superficial inguinal
c) Obturator
d) Paraaortic
Explanation: The lymphatic drainage of the ovary is through vessels that accompany the ovarian vessels to the paraaortic (lumbar) lymph nodes at the level of L1. This is because the ovaries originate in the posterior abdominal wall before descending into the pelvis during development. Hence, the correct answer is d) Paraaortic.
1. Which lymph nodes receive lymph from the uterus fundus along the ovarian vessels?
a) Internal iliac
b) External iliac
c) Paraaortic
d) Deep inguinal
Explanation: The fundus of the uterus drains partly along the ovarian vessels into the paraaortic lymph nodes. This pathway is significant during metastasis of endometrial carcinoma, where cancer may spread to upper abdominal nodes. Hence, the correct answer is c) Paraaortic.
2. Lymph from the lower part of the vagina drains into:
a) Paraaortic nodes
b) External iliac nodes
c) Internal iliac and superficial inguinal nodes
d) Deep inguinal nodes
Explanation: The lower part of the vagina drains into internal iliac and superficial inguinal nodes. The dual drainage is important in understanding the spread of vaginal carcinoma and infections. Hence, the correct answer is c) Internal iliac and superficial inguinal nodes.
3. Clinical case: A patient with ovarian carcinoma presents with enlarged nodes near the renal hilum. Which lymph nodes are involved?
a) Internal iliac
b) Paraaortic
c) External iliac
d) Superficial inguinal
Explanation: Ovarian carcinoma typically spreads to paraaortic lymph nodes near the renal hilum because ovarian lymphatics follow the ovarian vessels that ascend to the aortic region. This is a key diagnostic feature in imaging. Hence, the correct answer is b) Paraaortic.
4. Which of the following organs share similar lymphatic drainage as the ovary?
a) Uterus
b) Kidney
c) Rectum
d) Vagina
Explanation: Both ovary and kidney drain into paraaortic lymph nodes since both originate from the posterior abdominal wall embryologically. Understanding this helps trace metastatic spread patterns. Hence, the correct answer is b) Kidney.
5. Which structure carries ovarian lymphatics to paraaortic nodes?
a) Broad ligament
b) Suspensory ligament of ovary
c) Round ligament of uterus
d) Ovarian ligament
Explanation: Ovarian lymphatics travel through the suspensory ligament of the ovary (infundibulopelvic ligament) along with ovarian vessels to reach the paraaortic nodes. This ligament connects the ovary to the lateral pelvic wall. Hence, the correct answer is b) Suspensory ligament of ovary.
6. Clinical case: A 45-year-old woman with ovarian carcinoma shows paraaortic node metastasis. What is the route of lymphatic spread?
a) Along round ligament
b) Along ovarian vessels
c) Along uterine vessels
d) Along uterosacral ligament
Explanation: Ovarian lymphatics follow the course of ovarian vessels through the suspensory ligament to paraaortic nodes. This route allows tumor cells to spread to retroperitoneal nodes, detectable on CT scans. Hence, the correct answer is b) Along ovarian vessels.
7. Which lymph nodes drain the cervix of the uterus?
a) Paraaortic
b) External and internal iliac
c) Superficial inguinal
d) Deep inguinal
Explanation: The cervix drains into both external and internal iliac lymph nodes, a key pathway for cervical carcinoma spread. Hence, the correct answer is b) External and internal iliac.
8. Which lymph nodes receive lymph from the round ligament of uterus?
a) Deep inguinal
b) Paraaortic
c) Internal iliac
d) Obturator
Explanation: The round ligament passes through the inguinal canal and ends in the labia majora, so its lymphatic drainage terminates in the superficial inguinal nodes. This connection explains inguinal metastasis in uterine cancers. Hence, the correct answer is a) Deep inguinal.
9. Lymph from the body of uterus mainly drains to:
a) External iliac nodes
b) Superficial inguinal nodes
c) Paraaortic nodes
d) Obturator nodes
Explanation: The body of the uterus drains mainly into external iliac lymph nodes, with some lymph reaching paraaortic nodes via ovarian vessels. This dual drainage is important for surgical staging. Hence, the correct answer is a) External iliac nodes.
10. Clinical case: A woman with uterine carcinoma presents with palpable inguinal nodes. Which structure provides this lymphatic connection?
a) Ovarian ligament
b) Round ligament
c) Suspensory ligament of ovary
d) Uterosacral ligament
Explanation: The round ligament provides the connection between the uterus and the superficial inguinal lymph nodes through the inguinal canal. This explains why uterine cancers can spread to groin nodes. Hence, the correct answer is b) Round ligament.
Chapter: Thorax; Topic: Superior Thoracic Aperture; Subtopic: Structures Passing Through Superior Thoracic Aperture
Keyword Definitions:
• Superior thoracic aperture: The opening at the top of the thoracic cavity bounded by the first thoracic vertebra, first pair of ribs, and the superior border of the manubrium.
• Vagus nerve: A cranial nerve (X) that passes through the neck into the thorax supplying thoracic and abdominal organs.
• Thoracic duct: The main lymphatic channel that carries lymph from the lower body and left upper body to the venous system.
• Brachiocephalic artery: The first branch of the aortic arch, present on the right side only.
• Recurrent laryngeal nerve: A branch of the vagus nerve looping around arteries in the thorax to ascend to the larynx.
Lead Question - 2015
Which structure does not pass through superior thoracic aperture -
a) Right vagus
b) Right brachiocephalic artery
c) Thoracic duct
d) Right recurrent laryngeal nerve
Explanation: The right recurrent laryngeal nerve does not pass through the superior thoracic aperture. It loops around the right subclavian artery in the root of the neck, not within the thoracic inlet. The other structures—right vagus, thoracic duct, and right brachiocephalic artery—do traverse the superior thoracic aperture. Hence, the correct answer is d) Right recurrent laryngeal nerve.
1. The superior thoracic aperture is bounded posteriorly by:
a) Body of T2 vertebra
b) Manubrium sterni
c) Body of T1 vertebra
d) Clavicle
Explanation: The superior thoracic aperture is bounded posteriorly by the body of the T1 vertebra, laterally by the first pair of ribs, and anteriorly by the superior border of the manubrium. This ring-shaped opening allows passage of vital structures between the neck and thorax. Hence, the correct answer is c) Body of T1 vertebra.
2. Clinical case: A patient presents with compression of subclavian artery and vein at the thoracic inlet. This condition is called:
a) Thoracic outlet syndrome
b) Pancoast tumor
c) Cervical rib syndrome
d) Costoclavicular compression
Explanation: Compression of neurovascular structures at the thoracic inlet leads to thoracic outlet syndrome. Causes include a cervical rib, scalene muscle hypertrophy, or abnormal first rib. Symptoms include upper limb paresthesia and vascular insufficiency. Hence, the correct answer is a) Thoracic outlet syndrome.
3. Which of the following passes through the superior thoracic aperture?
a) Trachea
b) Esophagus
c) Thoracic duct
d) All of the above
Explanation: The trachea, esophagus, thoracic duct, and major vessels like subclavian arteries and veins pass through the superior thoracic aperture. These connect neck structures to thoracic organs, making the aperture clinically important for mediastinal and neck pathologies. Hence, the correct answer is d) All of the above.
4. The structure forming the lateral boundary of the superior thoracic aperture is:
a) First rib
b) Clavicle
c) Second rib
d) Sternum
Explanation: The first rib and its costal cartilage form the lateral boundaries of the superior thoracic aperture. It supports many vessels and nerves as they enter or exit the thorax. Hence, the correct answer is a) First rib.
5. Clinical case: A cervical rib compressing the inferior trunk of the brachial plexus produces which symptoms?
a) Upper limb paralysis
b) Tingling in fingers
c) Facial nerve palsy
d) Diaphragmatic paralysis
Explanation: A cervical rib can compress the inferior trunk of the brachial plexus, leading to tingling, pain, and weakness in the medial side of the hand and forearm. This is a feature of thoracic outlet syndrome. Hence, the correct answer is b) Tingling in fingers.
6. Which vessel does not pass through the superior thoracic aperture?
a) Subclavian artery
b) Internal thoracic artery
c) Thoracic duct
d) Aortic arch
Explanation: The aortic arch lies below the level of the superior thoracic aperture within the mediastinum. Other vessels such as subclavian arteries and thoracic duct pass through the aperture. Hence, the correct answer is d) Aortic arch.
7. The thoracic duct passes through which part of the diaphragm?
a) Caval opening
b) Esophageal opening
c) Aortic opening
d) Median arcuate ligament
Explanation: The thoracic duct passes through the aortic opening of the diaphragm along with the aorta and azygos vein at the T12 level. It then ascends through the posterior mediastinum to the thoracic inlet. Hence, the correct answer is c) Aortic opening.
8. Clinical case: A tumor compressing structures at the thoracic inlet may affect which nerve, causing hoarseness of voice?
a) Left recurrent laryngeal
b) Right recurrent laryngeal
c) Vagus
d) Phrenic
Explanation: The left recurrent laryngeal nerve loops under the aortic arch and ascends in the thoracic inlet. Compression can lead to vocal cord paralysis and hoarseness. Hence, the correct answer is a) Left recurrent laryngeal.
9. Which structure lies anterior to the scalenus anterior at the thoracic inlet?
a) Subclavian vein
b) Subclavian artery
c) Brachial plexus
d) Phrenic nerve
Explanation: The subclavian vein lies anterior to the scalenus anterior muscle, while the artery and brachial plexus pass posterior to it. This anatomical relationship is crucial in central venous catheterization. Hence, the correct answer is a) Subclavian vein.
10. Clinical case: During central venous catheter insertion, the needle is advanced too deeply, injuring a structure in the superior thoracic aperture. Which is most likely affected?
a) Subclavian vein
b) Pleura
c) Esophagus
d) Vagus nerve
Explanation: Over-insertion of a catheter in the subclavian route can puncture the pleura, causing pneumothorax. The pleural dome extends into the superior thoracic aperture above the first rib. Hence, the correct answer is b) Pleura.
Chapter: Thorax; Topic: Great Vessels and Fetal Circulation; Subtopic: Derivatives of Embryonic Ducts
Keyword Definitions:
• Ductus arteriosus: A fetal blood vessel connecting the pulmonary artery to the descending aorta.
• Ligamentum arteriosum: A fibrous remnant of the ductus arteriosus after birth.
• Ductus venosus: A fetal vessel that carries oxygenated blood from the umbilical vein to the inferior vena cava.
• Aorta: The main artery carrying oxygenated blood from the left ventricle to the body.
• Pulmonary artery: Carries deoxygenated blood from the right ventricle to the lungs.
Lead Question - 2015
Ligamentum arteriosum is derived from:
a) Ductus arteriosus
b) Ductus venosus
c) Ductus utriculosaccularis
d) Ductus reunions
Answer: a) Ductus arteriosus
Explanation: Ligamentum arteriosum represents the fibrous remnant of the fetal ductus arteriosus, which connects the pulmonary trunk to the descending aorta. After birth, it closes due to increased oxygen tension and reduced prostaglandin levels. Its location marks the site where the left recurrent laryngeal nerve loops beneath the aortic arch.
1. Which fetal structure becomes ligamentum teres hepatis after birth?
a) Umbilical vein
b) Umbilical artery
c) Ductus venosus
d) Vitelline vein
Answer: a) Umbilical vein
Explanation: The umbilical vein carries oxygenated blood from the placenta to the fetus. After birth, it closes and becomes the ligamentum teres hepatis, which runs within the free margin of the falciform ligament toward the liver. This closure helps redirect postnatal blood circulation to the liver.
2. The ductus arteriosus connects which two vessels in the fetus?
a) Aortic arch and pulmonary artery
b) Pulmonary artery and descending aorta
c) Pulmonary vein and left atrium
d) Aortic arch and right atrium
Answer: b) Pulmonary artery and descending aorta
Explanation: In fetal circulation, the ductus arteriosus diverts blood from the pulmonary artery to the descending aorta, bypassing the non-functional lungs. This ensures efficient oxygen delivery from the placenta to systemic circulation. It later forms the ligamentum arteriosum after birth.
3. Which of the following fetal structures closes soon after birth due to increased oxygen tension?
a) Foramen ovale
b) Ductus venosus
c) Ductus arteriosus
d) All of the above
Answer: d) All of the above
Explanation: Increased oxygen tension and reduced prostaglandins after birth cause closure of fetal shunts like the foramen ovale, ductus venosus, and ductus arteriosus. These closures redirect circulation through the lungs and liver, adapting the newborn to extrauterine life.
4. In a patient with patent ductus arteriosus (PDA), blood flows from:
a) Pulmonary artery to aorta
b) Aorta to pulmonary artery
c) Pulmonary vein to aorta
d) Aorta to right atrium
Answer: b) Aorta to pulmonary artery
Explanation: In PDA, the ductus arteriosus remains open, allowing blood to flow from the high-pressure aorta into the low-pressure pulmonary artery. This leads to left-to-right shunt, pulmonary hypertension, and potential heart failure if untreated.
5. A newborn presents with continuous machinery murmur. Which defect is most likely?
a) Patent foramen ovale
b) Patent ductus arteriosus
c) Ventricular septal defect
d) Atrial septal defect
Answer: b) Patent ductus arteriosus
Explanation: A continuous “machinery” murmur heard best at the left upper sternal border is characteristic of patent ductus arteriosus. This condition leads to excessive pulmonary blood flow and left heart volume overload, often requiring surgical or pharmacologic closure.
6. Which of the following prostaglandins helps maintain ductus arteriosus patency in the fetus?
a) PGE1
b) PGI2
c) PGF2α
d) TXA2
Answer: a) PGE1
Explanation: Prostaglandin E1 maintains ductus arteriosus patency during fetal life by relaxing smooth muscle in the ductal wall. After birth, decreased prostaglandin levels cause its closure. Clinically, PGE1 infusion is used to keep the ductus open in congenital heart defects needing ductal-dependent circulation.
7. Which structure passes beneath the ligamentum arteriosum?
a) Left recurrent laryngeal nerve
b) Right recurrent laryngeal nerve
c) Left phrenic nerve
d) Right vagus nerve
Answer: a) Left recurrent laryngeal nerve
Explanation: The left recurrent laryngeal nerve, a branch of the vagus, loops beneath the arch of aorta near the ligamentum arteriosum. It ascends in the tracheoesophageal groove toward the larynx, providing motor innervation to most intrinsic laryngeal muscles except cricothyroid.
8. Which congenital condition is associated with persistent ductus arteriosus?
a) Down syndrome
b) Turner syndrome
c) Rubella infection
d) Marfan syndrome
Answer: c) Rubella infection
Explanation: Maternal rubella infection during the first trimester is strongly linked to patent ductus arteriosus in the newborn. The virus affects vascular smooth muscle and endothelium, preventing normal closure. Such infants may also show cataracts, microcephaly, or deafness.
9. Surgical closure of PDA is commonly performed between:
a) Aortic arch and pulmonary artery
b) Left pulmonary vein and aorta
c) Pulmonary vein and right atrium
d) Pulmonary trunk and aortic root
Answer: a) Aortic arch and pulmonary artery
Explanation: PDA ligation is performed between the aortic arch and pulmonary artery, where the ductus arteriosus connects. Surgery or transcatheter device closure prevents excessive pulmonary circulation, reduces volume overload, and improves oxygenation. Proper timing minimizes complications and improves long-term outcomes.
10. Which change occurs immediately after closure of the ductus arteriosus at birth?
a) Decrease in pulmonary blood flow
b) Increase in pulmonary blood flow
c) Decrease in systemic resistance
d) Right-to-left shunt persists
Answer: b) Increase in pulmonary blood flow
Explanation: Closure of the ductus arteriosus eliminates the fetal right-to-left shunt, allowing full blood flow through the pulmonary circulation. This ensures efficient oxygenation and adaptation to postnatal life. The systemic resistance rises while pulmonary vascular resistance falls after birth.