Mastery of Circulatory System

Which of the following best explains why the left ventricle has a thicker wall than the right ventricle?

• A. It pumps blood to the lungs, which are nearby.

• B. It pumps oxygenated blood to the entire body.

• C. It needs to prevent blood from flowing backward.

• D. It stores more blood than the right ventricle.

Answer explanation

The left ventricle pumps blood to the entire body, so it needs a thick wall to generate higher pressure for this long-distance circulation.

2. What will most likely happen if the valves in veins do not function properly?

• A. Blood will circulate faster in the body.

• B. Blood will flow backward and pool in the veins.

• C. Arteries will collapse due to low pressure.

• D. Blood will leak into surrounding tissues directly.

Answer explanation

Veins have valves to prevent backflow. If valves fail, blood can pool (especially in the legs), causing swelling or varicose veins.

3. The reason oxygenated and deoxygenated blood are kept separate in the human heart is to —

• A. increase the speed of circulation.

• B. maintain high blood pressure in all chambers.

• C. ensure tissues get maximum oxygen supply.

• D. prevent the mixing of plasma and red blood cells.

Answer explanation

Ensure tissues get maximum oxygen supply.

Explanation: Separating oxygenated and deoxygenated blood ensures that tissues get blood rich in oxygen, making body functions more efficient.

4. Which statement accurately describes how capillaries support cell survival?

• A. They remove all the carbon dioxide from tissues instantly.

• B. They allow exchange of oxygen, nutrients, and wastes between blood and cells.

• C. They pump oxygen directly into the cells.

• D. They store white blood cells and release them during infections.

Answer explanation

Capillaries have thin walls that allow nutrients, gases, and wastes to move between blood and body cells — keeping cells alive and healthy.

5. The heart and lungs work closely together to supply oxygen to the body. Which of the following best describes this relationship?

• A. The lungs send oxygen directly into the left ventricle.

• B. The heart pumps deoxygenated blood to the lungs for oxygenation.

• C. The lungs circulate oxygen through arteries into the body.

• D. The heart sends oxygenated blood into the lungs for filtration.

Answer explanation

The right side of the heart pumps deoxygenated blood to the lungs, where it gains oxygen and returns to the heart to be pumped to the body.

6. If a person suffers a blockage in a coronary artery, the immediate risk is —

• A. damage to the muscles of the heart due to lack of oxygen.

• B. mixing of oxygenated and deoxygenated blood in the heart.

• C. inability to transport nutrients to the kidneys.

• D. increased blood flow to the brain.

Answer explanation

The coronary arteries supply the heart muscle itself with oxygen. A blockage starves heart tissue of oxygen, leading to a heart attack.

7. Which of the following changes would you expect in the body during vigorous exercise?

• A. Decrease in heart rate to conserve energy.

• B. Increase in blood flow to muscles for more oxygen and nutrients.

• C. Closure of capillaries in muscles to prevent overheating

• D. Reduction of red blood cell production to limit oxygen intake.

Answer explanation

During exercise, muscles need more energy. The heart pumps faster and more blood flows to muscles to supply extra oxygen and nutrients.

8. Which component of blood is mainly responsible for fighting infections?

• A. Red blood cells

• B. White blood cells

• C. Platelets

• D. Plasma

Answer explanation

White blood cells defend the body against infections by attacking bacteria, viruses, and other harmful invaders.

9. Which of these best describes the function of platelets?

• A. Carry oxygen to cells

• B. Aid in blood clotting to stop bleeding

• C. Attack bacteria and viruses directly

• D. Transport nutrients and hormones

Answer explanation

Platelets help form blood clots to seal wounds and stop bleeding when a blood vessel is damaged.

10. An athlete’s resting heart rate is lower than that of a non-athlete. What does this suggest about the athlete’s circulatory system?

• A. The athlete’s heart pumps less blood per beat.

• B. The athlete’s heart is weaker and beats slower.

• C. The athlete’s heart pumps more blood per beat efficiently.

• D. The athlete’s arteries are blocked and reduce circulation.

Answer explanation

A trained athlete’s heart is stronger and more efficient, pumping more blood with each beat. So, fewer beats are needed at rest.