BLOOD VESSEL NOTES

VASCULAR SYSTEM Take blood to tissues and back Arteries –carries blood away from heart Arterioles – “small arteries” found between arteries and capillaries

Capillaries – smallest of blood vessels and sites of gas exchange between blood and tissue cells connects arterioles and venules

Venules – “small veins” Connects capillaries and veins Veins –return blood toward heart

BLOOD VESSEL ANATOMY Tunica (layer) intima Endothelium (inner lining of blood vessels) Tunica media Middle, smooth muscle layer; controls (sympathetic nervous system) diameter of blood vessel

Tunic externa Outermost, fibrous connective tissue

DIFFERENCES BETWEEN BLOOD VESSEL TYPES Arteries Thickest layer; carry high pressure blood Blood pumped by force of heart

Veins Lumens (space inside of blood vessels) of veins are larger Use “milking” action of muscles to help move blood

Capillaries Only one cell thick Gas exchange between blood and tissue

Capillary beds (interweaving network of capillaries) consist of two types of vessels Vascular shunt – directly connects an arteriole to a venule True capillaries – gas exchange by diffusion (high to low concentration)