Which Blood Vessels Have Thin Walls And Contain Valves. Veins are blood vessels, and an essential part of the circulatory system that mainly functions by transporting deoxygenated blood back to the heart after arteries transports blood out. Blood vessels are the channels or conduits through which blood is distributed to body tissues.
The tunica externa, the tunica media, and the tunica intima.
Av valves of the heart open and close because of: Veins are large blood vessels which carry blood back to the heart. The vessels make up two closed systems of tubes that begin and end at the heart. The blood vessel wall consists of a single layer of endothelial cells that provides an interface between the blood and the smooth muscle forming the medial layer.