Oxygen starved tissues can release chemical signals into the blood that can change the diameter of nearby blood vessels delivering oxygen and nutrients to the tissues. In doing so, the blood vessels will respond through vasodilation (widening of the vessel). Which muscle type is responsible for this vasodilation?

Smooth muscles line the hollow internal structures such as blood vessels, airways, etc. These muscle cells lack striations and therefore, are called smooth muscle cells. The contraction of smooth muscle is involuntary and is under the regulation of the autonomic division of the nervous system and hormones.

For example, cells release vasoactive substances under the conditions of oxygen and nutrients deficiencies which in turn causes relaxation of smooth muscle cells of the blood vessels and widens them. The dilated blood vessels carry more oxygen and nutrients due to increased blood circulation in them.