Circulatory System.docx - Circulatory System Circulatory...

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Circulatory System Circulatory System- responsible for internal transport of substances to and from cells MAIN COMPONENTS Blood - composed of water, solutes, other elements in fluid CT Blood vessels - tubules of dif sizes that transport blood Heart - pump that provides pressure needed to keep blood flowing Can be open or closed o Closed - where heart and blood vessels are continually connected Most animals have this o Capillary beds - Smallest tubules blood flow rate is slow here Lymph vascular sys - supplementary sys o Cleans up excess fluids and proteins, r eturns them to circulatory sys ARTERIAL AND VENOUS SYS Walls of blood vessels (not capillaries)- have 3 layers o Tunica intima- innermost Has endothelium o Tunica media - smooth muscle cells + elastic fibers Diameter can be decreased or increased in vasoconstriction and vasodilation
o Tunica adventitia (externa)- outer layer made of loosely woven collagen fiber o Lumen - open space holding blood surrounded by layers Types of Vessels Elastic artery - includes aorta, major branches o Tunica media - has more elastin o Largest vessels in artery sys o Function : stretch when blood forced out, recoil in low pressure Receive blood from heart Deliver blood to more numerous muscular arteries Maintain blood pressure b/w heart contractions Muscular artery - includes arteries branching off elastic arteries o Tunica media - has more smooth muscle cells , fewer elastic fibers than elastic arteries o Function : regulate blood flow thru vasoconstriction/dilation Deliver blood to more numerous and smaller arterioles Regulate blood flow to organs Arterioles - mini arteries that branch out into capillaries o Tunica media - thin, mainly smooth muscle cells o Function : main vessels involved in vasoconstriction/dilation Control blood flow to capillaries Regulate peripheral resistance Capillaries o Walls - single layer of epithelial tissue forming tunic intima only So they can deliver oxygen and other nutrients in blood to cellular destinations thru diffusion o Bridge b/w arteriole and venous sys o Don’t operate own- form interweaving capillary beds Exchange nutrients w interstitial fluid Help regulate blood pressure Involved w thermoregulation Venules - thin tunica media + tunica intima o Wide lumen o Valves prevent backflow of blood o Function: carry blood back to heart Drain blood into fewer and larger veins Blood reservoir Veins o Functions Drain blood into fewer and larger veins and eventually back to heart Blood reservoir Artery vs vein o Vein s are not as strong as arteries
o Veins- to heart, arteries- away from heart o veins have valves BLOOD Function : helps maintain healthy internal enviro by carrying raw materials to cells and removing waste Helps stabilize internal pH , hosts lots of infection fighters Humans have about 5ish quarts of bloods Components Red/white blood cells , platelets, plasma Plasma - constitutes over half of the blood volume o Mostly water , serves as a solvent o Contains plasma

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