The largest artery in the human body is the aorta which is attached to the left ventricle of the heart muscle.
As oxygenated blood flows through the aorta it begins to move into a network of smaller arteries called arterioles and capillaries.
Veins are composed of three main layers:
- The tunica adventitia: The outermost layer of a vein is the tunica adventitia, or adventitia for short. This layer is the thickest layer of a vein’s lining and is made of loose connective tissues and an external elastic membrane. The adventitia fuses with surrounding tissue in the body.
- The tunica media: The tunica media, or media, is the middle layer of a vein’s wall. This layer is built of collagen, elastic fibers, and smooth muscle fibers.
- The tunica intima: The tunica intima, or intima, is the innermost layer of a vein’s lining. This is the thinnest layer of the vein’s wall and is composed of an internal elastic membrane and connective tissue.