Multiple Choice Questions (MCQs)
- Which coronary artery is more prominent in humans, swine, and horses?
a) Left coronary artery
b) Right coronary artery
c) Circumflex branch
d) Great cardiac vein
Answer: b) Right coronary artery - What percentage of cardiac output flows through the coronary arteries under normal conditions?
a) 4%
b) 10%
c) 15%
d) 40%
Answer: a) 4% - Which branch of the left coronary artery distributes about 80% of the total blood flow to the heart?
a) Anterior interventricular branch
b) Circumflex branch
c) Right marginal branch
d) Posterior interventricular branch
Answer: b) Circumflex branch - What happens to blood flow in the left coronary artery during systole?
a) Increases due to high coronary resistance
b) Decreases due to high coronary resistance
c) Remains constant
d) Increases significantly
Answer: b) Decreases due to high coronary resistance - Which vein drains blood supplied by the left coronary artery into the coronary sinus?
a) Thebesian veins
b) Great cardiac vein
c) Anterior cardiac veins
d) Right marginal vein
Answer: b) Great cardiac vein - What is the oxygen extraction rate by cardiac muscle under normal conditions?
a) 5 mL/100 mL of blood
b) 10–15 mL/100 mL of blood
c) 20 mL/100 mL of blood
d) 25 mL/100 mL of blood
Answer: b) 10–15 mL/100 mL of blood - What is the function of collateral vessels in coronary circulation?
a) Increase coronary resistance
b) Supply blood to ischemic myocardial regions
c) Drain blood directly into the coronary sinus
d) Regulate arterial pressure
Answer: b) Supply blood to ischemic myocardial regions - Which veins drain blood from the right coronary artery directly into the right atrium?
a) Great cardiac veins
b) Anterior cardiac veins
c) Thebesian veins
d) Posterior cardiac veins
Answer: b) Anterior cardiac veins - During exercise, coronary blood flow increases to what percentage of cardiac output?
a) 10%
b) 20%
c) 30%
d) 40%
Answer: d) 40% - Which artery supplies the AV node, atria, left ventricle, and interventricular septum?
a) Right coronary artery
b) Circumflex branch of the left coronary artery
c) Anterior cardiac artery
d) Posterior interventricular artery
Answer: b) Circumflex branch of the left coronary artery
Fill in the Blanks
- The right coronary artery is more prominent in ________, swine, and horses.
Answer: humans - The ________ vein drains blood from the left coronary artery into the coronary sinus.
Answer: great cardiac - During systole, blood flow in the left coronary artery ________ due to high coronary resistance.
Answer: decreases - Collateral vessels develop progressively from ________ in response to gradual coronary artery stenosis.
Answer: pre-existing capillaries - During exercise, coronary blood flow increases to ________% of cardiac output.
Answer: 40
True or False
- The left coronary artery is more prominent in dogs, cats, and ruminants.
Answer: True - Blood flow in the right coronary artery increases during diastole.
Answer: False - Thebesian veins drain small amounts of blood directly into the heart chambers.
Answer: True - Cardiac muscle extracts 5 mL of oxygen per 100 mL of blood under normal conditions.
Answer: False - The circumflex branch of the left coronary artery supplies about 80% of total blood flow to the heart.
Answer: True
Subjective Questions
- Explain the differences in blood flow variations between the left and right coronary arteries during systole and diastole.
Answer:- Left Coronary Artery: Blood flow decreases during systole due to high coronary resistance caused by ventricular muscle contraction. During diastole, the resistance decreases, allowing increased blood flow.
- Right Coronary Artery: Blood flow increases during systole because the contraction of the right ventricle does not significantly impede flow, and it decreases during diastole.
- Discuss the role of collateral vessels in coronary circulation.
Answer:
Collateral vessels are newly developed blood vessels that form from pre-existing capillaries in response to gradual coronary artery stenosis. They provide an alternative pathway for blood flow to ischemic myocardial regions, maintaining oxygen supply and minimizing tissue damage during restricted coronary circulation. These vessels are essential for adapting to long-term blockages and preventing severe ischemic conditions.