Question 1

Which of the following best describes the function of the atrioventricular (AV) valves in the human heart?

Accepted Answer

They prevent the backflow of blood from the ventricles into the atria during ventricular systole.

Question 2

During the cardiac cycle, what causes the 'dub' sound heard through a stethoscope?

Accepted Answer

Closure of the semilunar valves

Question 3

Which sequence correctly represents the pathway of electrical conduction in the heart?

Accepted Answer

SA node → AV node → AV bundle → AV bundle branches → Purkinje fibers

Question 4

Which plasma protein is primarily responsible for maintaining the blood’s osmotic strength?

Accepted Answer

Albumin

Question 5

What is the main function of erythropoietin in the human body?

Accepted Answer

Stimulates the bone marrow to increase production of red blood cells

Question 6

A person exposed to carbon monoxide (CO) is at risk because CO binds to hemoglobin more tightly than oxygen. Which equation best represents the competitive binding of CO and O$_2$ to hemoglobin?

Accepted Answer

$\mathrm{Hb} + \mathrm{CO} \rightarrow \mathrm{HbCO}$

Question 7

Which of the following is a correct statement about the life cycle of red blood cells?

Accepted Answer

Red blood cells are broken down in the spleen and liver, and their iron is recycled to the bone marrow.

Question 8

Which of the following white blood cells is most numerous in human blood?

Accepted Answer

Neutrophils

Question 9

Platelets play a central role in blood clotting. Which sequence best describes the process of clot formation?

Accepted Answer

Platelets form a plug, release chemicals, convert prothrombin to thrombin, which catalyzes the formation of fibrin from fibrinogen.

Question 10

Which blood vessel type is primarily responsible for the exchange of nutrients and wastes between blood and body cells?

Accepted Answer

Capillaries

Question 11

What is the primary mechanism by which blood returns to the heart from the lower extremities when a person is standing?

Accepted Answer

Contraction of skeletal muscles compresses veins and forces blood through one-way valves toward the heart.

Question 12

Which of the following best explains why capillary walls are only one cell thick?

Accepted Answer

To facilitate efficient diffusion of gases, nutrients, and wastes between blood and body cells.

Question 13

If the lymphatic system is blocked, as in elephantiasis, what is the most likely physiological consequence?

Accepted Answer

Accumulation of interstitial fluid, leading to swelling (edema) in affected tissues.

Question 14

Which of the following equations best represents the osmotic movement of water back into capillaries?

Accepted Answer

$	ext{Water moves from interstitial fluid} ightarrow 	ext{capillaries}$

Question 15

Which of the following is a function of the lymphatic system that is NOT performed by the circulatory system?

Accepted Answer

Transporting fats from the small intestine to the bloodstream

Question 16

Which of the following best describes the difference between arteries and veins?

Accepted Answer

Arteries have thicker, more elastic walls and carry blood away from the heart; veins have thinner walls and carry blood toward the heart.

Question 17

Which of the following is a real-world consequence of failing kidney function related to blood?

Accepted Answer

Anemia due to insufficient erythropoietin production

Question 18

Which of the following best describes the role of macrophages in the lymphatic system?

Accepted Answer

They engulf bacteria and cellular debris, helping to filter blood and lymph.

Question 19

Which of the following best explains why people with hemophilia are at risk for internal bleeding?

Accepted Answer

They lack a specific plasma protein required for blood clotting, preventing the formation of fibrin.

Question 20

Which of the following best describes the function of precapillary sphincters?

Accepted Answer

They regulate blood flow into capillary networks by opening and closing in response to local chemical changes.

Circulation and Blood: Structure, Function, and Regulation

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