BLOOD VESSEL NOTES VASCULAR SYSTEM Take blood to
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)
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