Question

Read the assertion and reason carefully to mark the correct option in question.

$\text{Assertion:}$ The valves of the heart (i.e., semilunar and atrio-ventricular valves) prevent any backward flow.

$\text{Reason:}$ The valves in the heart allows the flow of blood only in one direction, i.e. from the atria to the ventricles and from ventricles to the pulmonary artery or aorta.

• A. If assertion is true but the reason is false.
• B. If both assertion and reason are false.
• C. If both assertion and reason are true but the reason is not the correct explanation of the assertion.
• D. If both assertion and reason are true and the reason is the correct explanation of the assertion.

Answer 1

The correct option is D If both assertion and reason are true and the reason is the correct explanation of the assertion.

$\text{Assertion-Reason relation}$

Valves are the flap-like components of the heart which prevent the backflow of blood in the chambers of heart. There are two types of valves in heart- semilunar valves and atrio-ventricular valves.

Semilunar valves are the valves that guard the opening of the right and the left ventricles into the pulmonary artery and the aorta respectively while atrio-ventricular valves guard opening between atrium and ventricle of either side.

Hence, the given assertion- “The valves of the heart (i.e., semilunar and atrio-ventricular valves) prevent any backward flow” is true.

The flow of blood in heart is unidirectional. Semilunar valves allow flow of blood from ventricles to the pulmonary artery or aorta and atrio-ventricular valves allow flow of blood from atria to ventricles.

Hence, the given reason- “The valves in the heart allows the flow of blood only in one direction, i.e. from the atria to the ventricles and from ventricles to the pulmonary artery or aorta” is true and is the correct explanation of the given assertion.


$\text{Final answre}$
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.