Question

Blood returning to the mammalian heart in a pulmonary vein drains first into the

(A) right ventricle.
(B) right atrium.
(C) left ventricle.
(D) vena cava.
(E) left atrium.

Answer 1

Blood returning from the lungs via a pulmonary vein enters the heart through the left atrium.

Step-by-step explanation:

Blood returning to the mammalian heart in a pulmonary vein first drains into the left atrium (E). The right atrium receives blood from the systemic circuit that is low in oxygen, which then moves to the right ventricle and is pumped to the lungs via the pulmonary artery. The oxygenated blood from the lungs then returns through the pulmonary veins and enters the left atrium. The pulmonary circulation involves the movement of blood from the right atrium, to the right ventricle, to the lungs, and back to the heart's left atrium.

Answer 2

(E) left atrium.

Step-by-step explanation:

Pulmonary veins are veins that carry oxygenated blood from the lungs to the heart (left atrium). These veins are part of the pulmonary circuit:

Venae cavae are a vessels (vena cava interior and superior) that carry deoxygenated blood from the body to the right atrium. From the right atrium through the tricuspid valve the blood goes into the right ventricle. Then, from the right ventricle through the pulmonary valve the blood goes into the main pulmonary artery which carries deoxygenated blood to the lungs (to recieve oxygen). Oxygenated blood from the lungs travels to the heart: two pulmonary veins from each lung to the left atrium.