Biology
Assertion (A): The walls of the atria are thinner as compared to those of the ventricles.
Reason (R): The atria are the 'receiving chambers' as they receive blood and ventricles are the 'distributing chambers' as they pump blood into lungs and the thickest blood vessel - Aorta.
- Both A and R are true.
- Both A and R are false.
- A is true and R is false.
- A is false and R is true.
Answer
Both A and R are true.
Explanation — The atria have thinner walls as they only need to pump blood a short distance into the ventricles. Ventricles are bigger in size and their walls are thicker, elastic and muscular so as to efficiently pump blood to different parts of the body with much greater force.
Related Questions
Assertion (A): Blood is the fluid medium of the human circulatory system, responsible for transporting nutrients and excretory wastes, but it does not carry oxygen or carbon dioxide gases.
Reason (R): Oxygen and carbon dioxide gases are transported through the lymph vessels from one part of the body to the other since they are in gaseous states.
- Both A and R are true.
- Both A and R are false.
- A is true and R is false.
- A is false and R is true.
Assertion (A): None of the arteries carry deoxygenated blood in the human body.
Reason (R): Pulmonary artery carries deoxygenated blood from the right ventricle of the heart to the lungs.
- Both A and R are true.
- Both A and R are false.
- A is true and R is false.
- A is false and R is true.
Assertion (A): Capillaries are the finest blood vessels in the body, interconnecting arteries and veins.
Reason (R): The interconnection between arteries and veins is very significant because the exchange of water, nutrients, waste materials and respiratory gases occurs from arteries to veins and vice-versa through the capillaries only.
- Both A and R are true.
- Both A and R are false.
- A is true and R is false.
- A is false and R is true.
Match the items in Column A with those in Column B.
Column A Column B (a) Sino atrial node (i) Deoxygenated blood (b) Pulmonary veins (ii) Between right atrium and ventricle (c) Pulmonary artery (iii) Pacemaker (d) Tricuspid valve (iv) Between left atrium and ventricle (e) Biscuspid valve (v) Oxygenated blood