Three layers of arteries

The outermost layer is known as the

tunica externaformerly known as "tunica adventitia" and is composed of

connective tissue. Inside this layer is the

tunica media, or

media, which is made up of

smooth musclecells and elastic tissue. The innermost layer, which is in direct contact with the flow of blood is the

tunica intima, commonly called the

intima. This layer is made up of mainly

endothelial cells. The hollow internal cavity in which the blood flows is called the

lumen.