Blood Vessels Chapter 22

Introduction –Blood vessels Carry blood away from the heart - arteries Transport blood to tissues - capillaries Return blood to the heart – veins

Walls of Blood Vessels –3 layers Inner layer is endothelium = tunica intima Middle layer = tunica media Outer layer = tunica externa –Vasa vasorum are the vessels that supply the larger blood vessels

Walls of Blood Vessels

Arteries –Elastic arteries are the large arteries –Muscular arteries are the smaller arteries –Arterioles are very small, <0.5mm in diameter Capable of vasoconstriction and vasodilation

Systemic Arterial System

Major Arteries of the Trunk

Arteries of the Chest and Upper Extremity

Capillaries –The most important of the vessels All blood-tissue exchange occurs here –Tissue is entirely tunica intima –Three types Continuous – intact epithelial lining –Eg. Muscle & nervous tissue Fenestrated – have openings in their walls –Eg. Intestines & kidneys Sinusoids – lumen is larger; blood flow is slow –Eg. Liver, spleen, & bone marrow –Capillary beds with precapillary sphincters

Capillaries

Capillary Bed

Veins –Venules are very small, contain only tunica intima and tunica externa –Medium-sized veins –Large veins –Veins contain the same 3 layers as arteries Tunica media is much thinner than in arteries Tuna externa is the thickest layer –Some veins contain valves Prevent blood from flowing backwards

Systemic Venous System

Venous System of the Trunk and Upper Limb

Veins with Valves

Disorders –Varicose veins –Hypertension –Atherosclerosis

Atherosclerosis