Blood Vessels Arteries, Veins and Capillaries (Arterioles and Venules)

Arteries Carry blood away from the heart High pressure Carry oxygenated blood (except for the pulmonary artery) Thick muscular walls – 3 layers Thin tough outer layer Thick muscular middle layer Thin inner layer of cells Small lumen Do have a pulse No valves

Veins Carry blood toward the heart Low pressure Carry deoxygenated blood (except for the pulmonary artery) Thinner more flexible walls – 3 layers Thick tough outer layer Muscular middle layer Thin inner layer of cells Large lumen Does not have a pulse Valves present

Capillaries Penetrate all tissues Connect veins and arteries Very narrow – only one cell wide One cell thick walls – allows transport of oxygen and nutrient into body cells and wastes out of cells

Red Blood Cell The main function of red blood cells is to distribute oxygen to body tissues and to carry waste carbon dioxide back to the lungs. Biconcave: disc like cells Don’t contain a nucleus