Free Human Heart MCQs with Answers

1. The wall of the left ventricle is much thicker than that of the right ventricle because it

• 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 to the lungs a short distance away and at low pressure. More cardiac muscle means a higher pressure can be generated, which is why the left wall is roughly three times thicker. Blood enters both ventricles from the atria at low pressure.

2. The valve between the right atrium and the right ventricle is the

• 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 mitral. Both are held by chordae tendineae attached to papillary muscles, which stop them turning inside out when the ventricle contracts. The semilunar valves guard the exits into the pulmonary artery and the aorta, not the openings between chambers.

3. The muscle of the heart itself is supplied with blood by the

• 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 blood inside the chambers to supply it by diffusion. Blockage of one of these arteries starves a part of the muscle of oxygen and causes a heart attack. The pulmonary arteries carry deoxygenated blood away to the lungs.

4. A mature human red blood cell

• 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 flexibility to squeeze through capillaries. Having no mitochondria means the cell cannot use the oxygen it carries. Its life span is about 120 days, after which it is broken down in the liver and spleen; white cells, not red, can squeeze out of capillaries.

5. The human circulation is described as a double circulation because

• 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 the pump twice for each full journey. The advantage is that pressure lost in the lung capillaries is restored before the blood is sent to the body, so the systemic circuit can be supplied at high pressure. A fish has a single circulation and cannot do this.

6. A myocardial infarction, or heart attack, is most often caused by

• 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 it dies within minutes for lack of oxygen. Damaged cardiac muscle is not replaced, which is why the loss is permanent. Failure of the sinoatrial node disturbs rhythm rather than starving the muscle, and a leaking valve reduces efficiency without killing tissue.

7. The chambers of the heart that receive blood returning from the veins are the

• A. atria
• B. ventricles
• C. valves
• D. septum

Explanation: The right atrium collects deoxygenated blood from the venae cavae and the left atrium receives oxygenated blood from the pulmonary veins. Ventricles are the pumping chambers below, so direction of flow identifies each chamber.

8. The wall that separates the right ventricle from the left ventricle is the

• A. pericardium
• B. interventricular septum
• C. mitral valve
• D. aorta

Explanation: The muscular septum keeps oxygenated and deoxygenated blood completely separate, which is essential for the high efficiency of the mammalian double circulation. A hole in it, a septal defect, lets the two streams mix.

9. The valves found at the bases of the aorta and the pulmonary trunk are called

• A. bicuspid valves
• B. tricuspid valves
• C. semilunar valves
• D. atrioventricular valves

Explanation: Their three crescent shaped pockets fill with blood and snap shut when the ventricles relax, preventing backflow from the great arteries. The atrioventricular valves sit between atria and ventricles, a different position with different names.

10. The membrane that encloses and protects the heart is the

• A. pleura
• B. peritoneum
• C. meninges
• D. pericardium

Explanation: The pericardium anchors the heart in the chest and secretes fluid that lubricates its beating. The pleura covers the lungs and the peritoneum the abdominal organs, so the membrane names follow the organs they wrap.