Question 1

Which of the following best explains why some simple aquatic animals, such as flatworms, do not require a circulatory system?

Accepted Answer

Their bodies are thin and flat, maximizing surface area for direct diffusion of gases and nutrients.

Question 2

In insects, the tracheal system is responsible for gas exchange. What is the main limitation of this system regarding organism size?

Accepted Answer

Passive diffusion of gases down the tracheae limits the maximum size of the organism.

Question 3

Which of the following is a key advantage of a closed circulatory system over an open circulatory system?

Accepted Answer

Blood flow, nutrient delivery, and waste removal are more rapid and can be regulated to specific tissues.

Question 4

Which component of blood is primarily responsible for carrying oxygen?

Accepted Answer

Erythrocytes (red blood cells)

Question 5

A patient with hemophilia is at risk for excessive bleeding because:

Accepted Answer

One or more clotting factors do not function properly, preventing the formation of a stable fibrin clot.

Question 6

Which equation describes the conversion of carbon dioxide to bicarbonate in the blood?

Accepted Answer

$$\mathrm{CO_2$ + H_2O \rightarrow H_2CO_3 \rightarrow $$HCO_3$$^- + H^+}$$

Question 7

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

Accepted Answer

They regulate blood flow into capillary beds by contracting or relaxing.

Question 8

What is the primary reason that the left ventricle of the human heart is more muscular than the right ventricle?

Accepted Answer

It must generate higher pressure to overcome the greater resistance of the systemic circuit.

Question 9

During the cardiac cycle, what causes the 'lub-dub' sounds heard with a stethoscope?

Accepted Answer

Closure of heart valves during systole and diastole.

Question 10

Which of the following is a major risk factor for atherosclerosis?

Accepted Answer

High-fat diet, smoking, sedentary lifestyle, diabetes, and obesity.

Question 11

Which of the following statements about veins is correct?

Accepted Answer

Veins rely on skeletal muscle contraction and one-way valves to return blood to the heart.

Question 12

Which of the following best describes the process of blood clotting?

Accepted Answer

Platelet activation leads to conversion of prothrombin to thrombin, which polymerizes fibrinogen into fibrin.

Question 13

Which of the following is the most common way carbon dioxide is transported in human blood?

Accepted Answer

As bicarbonate ions in the plasma.

Question 14

What is the function of the sinoatrial (SA) node in the heart?

Accepted Answer

It acts as the primary pacemaker, initiating action potentials that cause atrial contraction.

Question 15

Which of the following is a consequence of a thrombus blocking a coronary artery?

Accepted Answer

A heart attack (myocardial infarction) due to decreased blood supply to the heart.

Question 16

Which of the following equations best represents the net outward force at the arteriole end of a capillary?

Accepted Answer

$$	ext{Net outward force} = 	ext{Blood pressure} - 	ext{Osmotic pressure}$$

Question 17

Which of the following is a function of platelets in the blood?

Accepted Answer

Initiating blood clotting by releasing enzymes and chemicals.

Question 18

Which of the following best describes the evolutionary advantage of separate pulmonary and systemic circuits in birds and mammals?

Accepted Answer

Oxygenated and deoxygenated blood cannot mix, maximizing gas exchange and allowing different pressures in each circuit.

Question 19

Which of the following is a major function of plasma proteins such as albumin and fibrinogen?

Accepted Answer

Osmotic balance, pH buffering, and clotting responses.

Circulatory Systems: Structure, Function, and Disease

Study Guide - Practice Questions