Heart: valves, vessels and nodal tissue Blood vessels: structure and function

Heart Valves

Coronary Blood vessels

Nodal Tissue

Blood vessels: Structure and Function Arteries Arterioles Capillary Venules Veins

Blood vessels : Arteries Arteries: thick, elastic walls Lumen: holds blood 3 layers: outer connective tissue middle layer of smooth muscle & elastic fibers (stretch) inner endothelium allows stretching/response to large change in pressure

Arterioles carry blood away from heart/ between arteries and capillaries vasodilation and vasoconstriction allows vessels to change diameter, affecting blood pressure and heat loss 3 layers: middle layer mostly smooth muscle surrounded by elastic fibers. Vasodilation= elastic fibers relax=increase in diameter=decrease in blood pressure Vasoconstriction= elastic fibers contract= decrease in diameter= increase in blood pressure

Capillaries exchange of nutrients and wastes, oxygen and carbon dioxide via diffusion connect arterioles to venules one cell thick facilitates diffusion highly branched capillary beds increase surface area sphincters at beginning of some beds regulates blood flow affecting blood pressure and tissue use of nutrients & oxygen

Venules conduct low pressure blood from capillaries to veins thin walls… middle layer not well developed don’t need to be thick-walled or elastic since blood in them is under very low pressure

Veins Carry low-pressure blood towards heart Act as blood reservoirs. Iif blood pressure is too low, can constrict and force more blood through system, increasing b.p. 3 layers. thin elastic layer due to low b.p. one way valves prevent backflow of blood