Question

which step occurs first in the vascular system?
o a. blood leaves the left side of the heart via the aorta.
o b. blood leaves the right side of the heart via the pulmonary artery.
o c. blood either leaves the aorta and goes to the upper body and head, or travels to the lower body.
o d. blood loses carbon dioxide, picks up oxygen in the lungs, and then returns to the hearts left side via the pulmonary vein.

Explanation:

The vascular system's cycle starts with de - oxygenated blood leaving the right side of the heart. The pulmonary artery is the vessel through which this blood exits. Option a is incorrect as blood leaves the left side of the heart (oxygenated) later in the systemic circulation. Option b is wrong because the aorta is not the vessel for blood leaving the right side of the heart. Option d describes a later step (gas exchange in the lungs).

Answer:

C. Blood leaves the right side of the heart via the pulmonary artery.