Free Circulation MCQs with Answers

• A. holds a far larger volume of blood
• B. must pump blood against the much greater resistance of the systemic circuit
• C. contains more valves than the right ventricle
• D. receives blood at a higher pressure from the left atrium

Explanation: Both ventricles eject the same volume with each beat, but the left has to drive blood through the whole body while the right only sends it…

• A. tricuspid valve
• B. bicuspid valve
• C. aortic semilunar valve
• D. pulmonary semilunar valve

Explanation: The right atrioventricular valve has three flaps and is therefore called tricuspid, while the left one has two and is called bicuspid or…

• A. pulmonary arteries
• B. coronary arteries
• C. blood passing through the chambers
• D. superior vena cava

Explanation: The coronary arteries branch from the base of the aorta and spread over the heart wall, because the myocardium is far too thick for the…

• A. atrioventricular node
• B. bundle of His
• C. sinoatrial node in the wall of the right atrium
• D. network of Purkinje fibres

Explanation: The sinoatrial node depolarises spontaneously about seventy times a minute and sets the rhythm, which is why the heartbeat is myogenic and…

• A. slows the overall heart rate
• B. prevents the impulse from reaching the ventricles at all
• C. allows the semilunar valves to open early
• D. gives the atria time to empty into the ventricles before the ventricles contract

Explanation: A delay of about a tenth of a second lets atrial systole finish and the ventricles fill completely, so the following ventricular…

• A. 5 dm3 per minute
• B. 0.5 dm3 per minute
• C. 14 dm3 per minute
• D. 50 dm3 per minute

Explanation: Cardiac output is stroke volume multiplied by heart rate, so 70 cm3 times 72 gives 5,040 cm3 per minute, which is about 5 dm3.

• A. blood rushing into the atria
• B. the closure of the semilunar valves
• C. contraction of the atrial walls
• D. the closure of the atrioventricular valves at the start of ventricular systole

Explanation: When the ventricles begin to contract the pressure inside them rises above atrial pressure, the tricuspid and bicuspid valves snap shut…

• A. Superior vena cava
• B. Hepatic vein
• C. Pulmonary vein
• D. Renal vein

Explanation: The pulmonary vein returns freshly oxygenated blood from the lungs to the left atrium, so it is the exception to the rule that veins carry…

• A. veins carry deoxygenated blood
• B. blood in veins is at low pressure and would otherwise flow backwards
• C. arteries have thinner walls
• D. veins lie closer to the skin

Explanation: By the time blood reaches the veins the pressure created by the heart has largely been lost in the capillaries, so flow depends on the…

• A. one cell thick, formed of a single layer of endothelium
• B. made of smooth muscle that contracts rhythmically
• C. lined with valves at close intervals
• D. thick and elastic to withstand pressure

Explanation: A capillary wall is a single layer of flattened endothelial cells, giving a diffusion distance of well under a micrometre, and the…

• A. capillaries
• B. venules
• C. aorta
• D. venae cavae

Explanation: Pressure is greatest as blood leaves the left ventricle into the aorta and falls steadily along the circuit, with the sharpest drop across…

• A. 80/120 mm Hg
• B. 120/80 mm Hg
• C. 200/100 mm Hg
• D. 60/40 mm Hg

Explanation: The larger figure is the systolic pressure during ventricular contraction and the smaller is the diastolic pressure while the ventricles…

• A. carries oxygenated blood to the liver
• B. carries blood directly from the heart to the liver
• C. has thicker walls than any artery
• D. begins in the capillaries of the gut and ends in the capillaries of the liver

Explanation: A portal vessel runs between two capillary beds instead of returning blood to the heart, so absorbed glucose and amino acids reach the…

• A. tissue fluid that drains into blind ending lymph capillaries
• B. blood plasma filtered by the kidney
• C. the secretion of the lymph nodes
• D. bile leaving the liver

Explanation: Plasma is forced out of the capillaries at their arterial end to become tissue fluid, most of which returns to the blood at the venous…

• A. pump lymph around the body
• B. produce red blood cells
• C. filter lymph and provide a site where lymphocytes multiply
• D. absorb glucose from the small intestine

Explanation: Nodes are packed with macrophages that trap bacteria and debris carried in the lymph, and with lymphocytes that divide there when an…

• A. glucose
• B. amino acids
• C. water and mineral ions
• D. the products of fat digestion

Explanation: Fatty acids and glycerol are reassembled into fats inside the villus cells and packaged into droplets too large for the blood capillaries…

• A. blood cannot leave the limb through the veins
• B. excess tissue fluid cannot be drained away and accumulates
• C. the arteries dilate and overfill the tissue
• D. plasma proteins are digested in the tissue spaces

Explanation: The lymphatic system is the only route by which the surplus tissue fluid returns to the blood, so blocking it lets fluid build up in the…

• A. has no nucleus and is biconcave in shape
• B. has a large nucleus and many mitochondria
• C. is amoeboid and can leave the capillaries
• D. lives for about ten days

Explanation: Losing the nucleus makes room for more haemoglobin, and the biconcave disc shape gives a large surface area for gas exchange and enough…

• A. the heart has two sides
• B. arteries and veins run side by side
• C. blood passes through the heart twice in one complete circuit of the body
• D. there are two types of blood cell

Explanation: Blood goes heart to lungs to heart in the pulmonary circuit and then heart to body to heart in the systemic circuit, so it passes through…

• A. failure of the sinoatrial node to fire
• B. leakage of the bicuspid valve
• C. an increase in the number of red blood cells
• D. blockage of a coronary artery by a thrombus on an atherosclerotic plaque

Explanation: Fatty plaques narrow a coronary artery over years, and when one ruptures a clot forms and cuts off the blood supply, so the muscle beyond…