Which statement regarding the mammalian heart is correct? A) In the adult heart, blood in the right chambers of the heart cannot enter the left chambers without passing through the lungs. B) Blood arrives at the heart via the ventricles. C) Oxygen-loaded blood moves only through the right side of the heart. D) When the right atrium contracts, it forces blood into the left atrium. E) Blood is pumped from the heart via the atria.

In the adult heart, blood in the right chambers of the heart cannot enter the left chambers without passing through the lungs. (Ans. A)

Explanation:

In heart, heart muscle cells is responsible for the circulating the blood throughout the body. The heart contains four chambers, two upper called as atrium and two lower called as ventricle, 1 atrium and 1 ventricle present on both right and left sides of the heart.

Blood which is returning from other parts of the body and is no longer oxygen rich, enters from the top right chamber of the heart. Than this blood is pumped into the right vertical and through the pulmonary artery into the lungs for absorb more oxygen. This oxygen rich blood is then pumped into the top left chamber present in the heart, and then into the lower left chamber before being pumped out into the body from the aorta.

So, the answer is A.