A vein. Arteries have additional muscular layers to withstand the higher pressures of blood leaving the heart, veins lack this layer due to low-pressure environments.
Smooth muscle
vein
Tunica interna
Vasospasm-- Narrowing of a blood vessel caused by a spasm of the smooth muscle of the vessel wall.
Tunica Externa
An abdominoscrotal muscle is another name for the cremaster muscle, a thin muscle attached to the testicles.
There more thin filaments than thick filaments in smooth muscle. The ratio is of the thin to thick filaments in the smooth muscle is approximately 15:1.
an increase in vessel diamete
vasoconstriction
An artery is a vessel with a thick medial layer, consisting of smooth muscle to allow for constriction or dilation in order to control blood flow through the vessel.
thick and thin bands (lines) of filaments.
The Arteries