Blood flow through capillaries is controlled by
A) one-way valves.
B) precapillary sphincters only.
C) smooth muscle in the walls of arterioles only.
D) precapillary sphincters and smooth muscle in the walls of arterioles.

Question

Quizplus · Accepted Answer

Blood flow through capillaries is controlled by two mechanisms: the precapillary sphincters and the smooth muscle in the walls of arterioles. The precapillary sphincters are located at the entrance of each capillary and can either constrict or relax to regulate blood flow. The smooth muscle in the walls of arterioles can also constrict or relax to regulate blood pressure and flow. Therefore, the correct choice is D – precapillary sphincters and smooth muscle in the walls of arterioles.

Blood Flow Through Capillaries Is Controlled by