MCQ 41:
What is the primary function of the vena cava?
A) Carry oxygenated blood to the heart
B) Carry deoxygenated blood to the heart
C) Supply blood to the lungs
D) Pump blood to the body
Answer: B) Carry deoxygenated blood to the heart
Explanation: The superior and inferior vena cavae are large veins that carry deoxygenated blood from the body back to the right atrium of the heart.
MCQ 42:
What is the primary component of lymph?
A) Red blood cells
B) Plasma
C) White blood cells
D) Tissue fluid
Answer: D) Tissue fluid
Explanation: Lymph is primarily composed of tissue fluid that has leaked from blood vessels, along with white blood cells that help in immune function.
MCQ 43:
Which of the following is true regarding capillaries?
A) They have thick walls to handle high pressure.
B) They allow exchange of substances between blood and tissues.
C) They only carry oxygenated blood.
D) They are larger than arteries.
Answer: B) They allow exchange of substances between blood and tissues.
Explanation: Capillaries have thin walls that facilitate the exchange of oxygen, carbon dioxide, nutrients, and waste products between the blood and surrounding tissues.
MCQ 44:
Which blood component is essential for transporting oxygen?
A) Plasma
B) Leukocytes
C) Erythrocytes
D) Thrombocytes
Answer: C) Erythrocytes
Explanation: Erythrocytes, or red blood cells, are specialized to transport oxygen throughout the body using hemoglobin.
MCQ 45:
What is the main function of the circulatory system’s valves?
A) Increase blood pressure
B) Prevent blood from flowing backward
C) Pump blood to the lungs
D) Exchange gases
Answer: B) Prevent blood from flowing backward
Explanation: The valves in the heart and veins ensure that blood flows in one direction, preventing backflow and maintaining efficient circulation.
MCQ 46:
What is the term for the contraction of the heart?
A) Diastole
B) Systole
C) Arrhythmia
D) Hemostasis
Answer: B) Systole
Explanation: Systole refers to the phase of the cardiac cycle during which the heart muscle contracts and pumps blood out of the chambers.
MCQ 47:
Which vitamin is essential for the synthesis of clotting factors in the liver?
A) Vitamin A
B) Vitamin B12
C) Vitamin K
D) Vitamin D
Answer: C) Vitamin K
Explanation: Vitamin K is crucial for the synthesis of several proteins that mediate blood coagulation (clotting).
MCQ 48:
What happens during diastole?
A) The heart relaxes and fills with blood.
B) The heart contracts and pumps blood.
C) Blood pressure decreases significantly.
D) Oxygen is absorbed in the lungs.
Answer: A) The heart relaxes and fills with blood.
Explanation: Diastole is the phase of the cardiac cycle when the heart muscle relaxes and the chambers fill with blood.
MCQ 49:
Which type of blood vessel has the highest pressure?
A) Capillaries
B) Veins
C) Arteries
D) Venules
Answer: C) Arteries
Explanation: Arteries carry blood away from the heart under high pressure generated by heart contractions, especially the aorta.
MCQ 50:
What is the main role of the spleen in the circulatory system?
A) Producing insulin
B) Filtering blood and recycling iron
C) Pumping blood
D) Regulating blood pressure
Answer: B) Filtering blood and recycling iron
Explanation: The spleen filters blood, removing old or damaged red blood cells and recycling iron for future use in hemoglobin production.
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