The beginning of a true capillary is surrounded by a precapillary sphincter. The opening and closing of precapillary sphincters is controlled by .

Local Chemical condition

Explanation:

Precapillary sphincter is a small smooth muscles that regulates the flow of blood into the capillaries.

Blood flows to the surrounding branches of the capillary due to the fact that surrounding capillaries require oxygen when the sphincters are open and the blood flows directly from the arteriole( which is a small artery) to the venule( which is a small vein) when the sphincters are closed

scientists have discovered that hiv does not cause aids by the virus's direct effect on the host's immune cells, but rather through the cells' lethal influence on one another. researchers from the gladstone institutes have revealed that hiv does not cause aids by the virus's

the corpus luteum secretes estrogens and progesterone. the latter hormone causes changes in the uterus that make it more suitable for implantation of the fertilized ovum and the nourishment of the embryo. if the egg is not fertilized, the corpus luteum becomes inactive after 10–14 days, and menstruation occurs.

i hope this : )