MCQ 51:
Which structure prevents backflow of blood in the heart?
A) Septum
B) Valves
C) Chordae tendineae
D) Myocardium
Answer: B) Valves
Explanation: Heart valves, located between the atria and ventricles as well as at the exits of the ventricles, prevent backflow of blood during contractions.
MCQ 52:
What is the main purpose of red blood cell shape?
A) Flexibility to navigate through capillaries
B) Increase oxygen binding capacity
C) Decrease cell size
D) Facilitate immune function
Answer: A) Flexibility to navigate through capillaries
Explanation: The biconcave shape of red blood cells provides flexibility, allowing them to squeeze through narrow capillaries while maximizing surface area for gas exchange.
MCQ 53:
Which component of blood is involved in the immune response?
A) Plasma
B) Erythrocytes
C) Thrombocytes
D) Leukocytes
Answer: D) Leukocytes
Explanation: Leukocytes, or white blood cells, are key players in the immune system, defending the body against infections and foreign invaders.
MCQ 54:
What is the role of the intercalated discs in cardiac muscle?
A) Prevent backflow
B) Facilitate electrical impulses
C) Support blood vessel growth
D) Store calcium ions
Answer: B) Facilitate electrical impulses
Explanation: Intercalated discs are specialized connections between cardiac muscle cells that allow for rapid transmission of electrical impulses, ensuring coordinated heart contractions.
MCQ 55:
Which condition is characterized by low red blood cell count?
A) Leukemia
B) Anemia
C) Thrombocytopenia
D) Hemophilia
Answer: B) Anemia
Explanation: Anemia is a condition marked by a deficiency in the number or quality of red blood cells, leading to reduced oxygen delivery to tissues.
MCQ 56:
What is the role of the aortic valve?
A) Prevent backflow from the aorta to the left ventricle
B) Allow blood to flow from the left atrium to the left ventricle
C) Prevent backflow from the pulmonary artery
D) Regulate blood flow to the coronary arteries
Answer: A) Prevent backflow from the aorta to the left ventricle
Explanation: The aortic valve prevents the backflow of blood from the aorta into the left ventricle after contraction.
MCQ 57:
Which of the following vessels has valves?
A) Arteries
B) Capillaries
C) Veins
D) All of the above
Answer: C) Veins
Explanation: Valves are present in veins to prevent backflow of blood, particularly in the limbs where blood must travel against gravity.
MCQ 58:
What is the role of the coronary arteries?
A) Supply blood to the lungs
B) Supply blood to the heart muscle
C) Carry deoxygenated blood to the heart
D) Filter blood in the spleen
Answer: B) Supply blood to the heart muscle
Explanation: Coronary arteries branch off from the aorta and supply oxygenated blood to the heart muscle itself.
MCQ 59:
What term describes the volume of blood pumped by the heart per minute?
A) Stroke volume
B) Cardiac output
C) Blood pressure
D) Heart rate
Answer: B) Cardiac output
Explanation: Cardiac output is the volume of blood that the heart pumps in one minute, calculated as heart rate multiplied by stroke volume.
MCQ 60:
Which blood vessel is responsible for nutrient and gas exchange?
A) Artery
B) Vein
C) Capillary
D) Lymphatic vessel
Answer: C) Capillary
Explanation: Capillaries are the sites of exchange of oxygen, carbon dioxide, nutrients, and waste products between blood and tissues.
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