Blood vessels alter blood flow by vasoconstriction and vasodilation. Chemicals that mediate vasoconstriction include serotonin and norepinephrine among others. Vasoconstriction works by contraction...
It always flows the same way. It leaves the heart through the Aorta. This is the largest artery in the body. The blood then branches off into progressively smaller arteries until it gets to the...
The blood vessels are made up of an internal layer of muscle fibers, which are capable of contraction and relaxation. The contraction of the muscles reduces the lumen size of the vessel, making the...