Blood Vessels

◦ 5 main types of blood vessels

◦ Arteries

◦ Arterioles

◦ Capillaries

◦ Venules

◦ Veins

Blood Vessels – Structure and Functions

◦ The wall of blood vessels consists of 3 layers, called tunics

◦ Tunica externa (tunica adventitia)

◦ The outer coat - consists of collagenous and elastic fibres

◦ Tunica media

◦ The middle coat - consists mainly of smooth muscle with elastic fibres and some collagen fibres

◦ Tunica interna (tunica intima)

◦ The inner lining - consists of a layer of endothelium & provides a smooth surface over which the blood can flow without clotting

Tortora & Nielsen, 2017

7 Tunica Interna (Tunica Intima)

◦ Tunic =garment or coat;

◦ Interna or Intima =innermost

◦ consists of Endothelium

◦ Functions

◦ acts as a selectively permeable barrier

◦ materials entering or leaving the bloodstream

◦ secretes chemicals

◦ stimulate dilation or constriction of the vessel

◦ repels blood cells and platelets

◦ flow freely without sticking to the vessel wall