Free Blood Vessels MCQs with Answers

1. Which vessel carries oxygenated blood despite being called a vein?

• 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 deoxygenated blood. The naming depends on direction of flow rather than on oxygen content: a vein carries blood towards the heart and an artery away from it. Its partner exception is the pulmonary artery, which carries deoxygenated blood.

2. Valves are present in veins but not in arteries because

• 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 squeezing of skeletal muscles, and the pocket valves ensure that this squeezing pushes blood only towards the heart. Arteries need no valves because the pressure from ventricular systole is high enough to keep blood moving in one direction. Failure of these valves produces varicose veins.

3. Exchange of materials between blood and tissues occurs only in capillaries because their walls are

• 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 enormous total surface area and slow flow complete the design. Arteries and veins have thick walls of muscle and elastic tissue that make exchange impossible, so they are transport vessels only. The narrowness of a capillary also forces red cells through in single file.

4. Blood pressure is highest in 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 the arterioles and capillaries because of their resistance and their vast combined cross sectional area. By the time blood reaches the venae cavae the pressure is close to zero. This falling gradient is what keeps blood flowing in one direction.

5. A normal resting blood pressure for a young adult is recorded as

• 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 are relaxed and filling, and the systolic value is always written first. A sustained reading at or above about 140/90 is hypertension, which strains the heart and damages arteries, kidneys and the retina. Reversing the two numbers is the classic careless error.

6. The hepatic portal vein is unusual because it

• 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 liver before entering the general circulation. This lets the liver regulate blood glucose and remove toxins straight after a meal. The blood it carries is deoxygenated, since it has already passed through the intestinal capillaries.

7. The left ventricle pumps blood to the

• A. Lungs
• B. Body
• C. Right atrium
• D. Pulmonary artery

Explanation: The left ventricle pumps oxygenated blood through the aorta to the entire body (systemic circulation).

8. The SA node is the

• A. AV bundle
• B. Pacemaker of the heart
• C. Valve of the heart
• D. Coronary artery

Explanation: The sinoatrial (SA) node in the right atrium is the natural pacemaker, initiating each heartbeat.

9. Which blood vessel has the thickest muscular wall?

• A. Vena cava
• B. Pulmonary vein
• C. Aorta
• D. Capillary

Explanation: The aorta has the thickest wall to withstand the high pressure of blood ejected from the left ventricle.

10. Tissue fluid is formed by

• A. Active transport
• B. Ultrafiltration from capillaries
• C. Secretion by cells
• D. Osmosis only

Explanation: Tissue fluid forms by ultrafiltration from arterial ends of capillaries due to hydrostatic pressure.