Question

multiple choice question
what controls the relaxation and contraction of the precapillary sphincters?

the pressure of the colloid osmotic component of capillary exchange
the availability of oxygen and nutrients to the tissues surrounding the capillary network
the innervation of the surrounding skeletal muscles
the force of contraction of the ventricles

Explanation:

Precapillary sphincters regulate blood flow into capillary beds. They relax or contract based on the metabolic needs of the surrounding tissues, which are signaled by the availability of oxygen and nutrients. Low oxygen and nutrient levels in the tissue cause the sphincters to relax, allowing more blood flow, while high levels cause them to contract, reducing blood flow.

Answer:

The availability of oxygen and nutrients to the tissues surrounding the capillary network