Free Human Heart MCQs with Answers

21. Arteries have thick walls rich in elastic fibres because they

• A. carry deoxygenated blood only
• B. must collapse when empty
• C. must withstand and smooth out the high pressure of blood from the heart
• D. need to store lymph between meals

Explanation: Each heartbeat stretches the elastic walls, which then recoil and keep blood moving between beats, converting a pulsatile flow into a steadier one. Veins work at low pressure and so have thinner walls.

22. Blood flows most slowly in the capillaries because their

• A. walls are unusually thick
• B. total cross sectional area is enormous
• C. internal pressure is the highest of any vessel
• D. diameter exceeds that of the aorta

Explanation: Although each capillary is microscopic, together they present a huge total area, so the same volume of blood spreads out and slows, allowing time for exchange. Slow flow follows from area, not from wall thickness.

23. The vessel that carries deoxygenated blood from the heart to the lungs is the

• A. pulmonary artery
• B. pulmonary vein
• C. aorta
• D. coronary artery

Explanation: The pulmonary artery is the exception to the rule that arteries carry oxygenated blood, since it carries blood to the lungs to be oxygenated. The pulmonary vein reverses the pattern, carrying oxygenated blood back as a vein.

24. The largest artery of the human body is the

• A. carotid artery
• B. aorta
• C. femoral artery
• D. renal artery

Explanation: The aorta, about 2.5 cm in diameter, receives the entire output of the left ventricle and branches to every organ. All other systemic arteries are branches of it.

25. The superior and inferior venae cavae empty deoxygenated blood into the

• A. left ventricle
• B. left atrium
• C. right atrium
• D. aorta

Explanation: The venae cavae collect blood from the upper and lower body and deliver it to the right atrium, from where it passes to the right ventricle and on to the lungs. The left atrium receives blood from the lungs instead.

26. Blood pressure is lowest in the

• A. aorta
• B. arteries
• C. arterioles
• D. venae cavae

Explanation: Pressure falls steadily through arteries, arterioles and capillaries as energy is lost to friction, reaching near zero in the great veins. This is why venous return depends on valves, muscle contraction and breathing rather than on pressure.

27. The build up of fatty deposits called plaques within the walls of arteries is known as

• A. atherosclerosis
• B. arthritis
• C. anaemia
• D. haemophilia

Explanation: Plaques of cholesterol and debris narrow and stiffen arteries, raising blood pressure and predisposing to clots that cause heart attacks and strokes. Controlling diet, smoking and blood pressure slows the process.

28. The largest lymphoid organ of the body, which filters blood and removes worn out red blood cells, is the

• A. tonsils
• B. spleen
• C. thymus
• D. lymph node

Explanation: The spleen sits in the abdomen and acts on blood the way lymph nodes act on lymph, trapping pathogens and recycling old erythrocytes. Its size and blood filtering role distinguish it from the other lymphoid organs.

29. The tonsils are lymphoid tissues located

• A. along the spinal cord
• B. in the thorax around the heart
• C. in the throat, guarding the entrances of the respiratory and digestive tracts
• D. inside the bone marrow

Explanation: Their position at the back of the mouth and nose lets them sample inhaled and swallowed material and mount early immune responses. This sentinel role explains why they swell during throat infections.

30. The lymphatic system finally returns lymph to the blood at the

• A. capillaries of the tissues
• B. aorta
• C. pulmonary vein
• D. subclavian veins near the neck

Explanation: The thoracic duct and right lymphatic duct empty lymph into the subclavian veins, restoring fluid and proteins that leaked from the capillaries. Without this return, tissues would swell with trapped fluid.