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three principle categories of blood vessels |
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arteries, veins & capillaries |
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arteries |
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efferent vessels- carry blood away from heart |
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veins |
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afferent vessels- carry blood back to heart |
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capillaries |
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microscopic, thin walled vessels that connect the smallest arteries to teh smallest veins |
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walls of arteries are composed of 3 layers of |
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tunics |
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tunica interna |
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lines inside of the vessel- exposed to blood- consists of simple squamos epith called endothelium |
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tunica media |
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mid layer- thickest-smooth muscle, collagen,elastic tiss- strengthen the vess and prevent bp from rupturing them & to provide vasomotion |
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vasomotion |
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changes in diameter of a blood vessel |
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tunica externa |
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outer most layer- loose connect tiss often merges w. neigh vess anchors the vess and provides pass4small nerves, lymph vess& smaller blood vess |
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vasa vasorum |
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small vessels that supply blood to at least the outer half of the wall of a larger vessel |
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resistance vessles |
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a.k.a arteries. bc relatively strong resilient tiss struct that resists high bp- constructed to w/stand surges |
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conducting ( elastic or large) arteries |
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BIGGEST-expand during ventricular systole to receive blood& recoil during diastole.sub to highest bp& have elastic tiss |
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Distributing (muscular or medium) arteries |
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smaller branches that distrib blood to specif organs- interestate highway- 40 layers of smooth musc |
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resistance ( small) arteries |
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too variable in # and location to be given individual names- 25 layers of smooth musc & relatively little elastic tiss |
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arterioles |
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smallest of the resistance arteries 40-200Mm w/ only one to 3 layers of smooth muscle |
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metarterioles |
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short vessels that link arterioles and capillaries. have individual muscle cells spaced a short distance apart each forming a precap sphinct |
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precapillary sphincter |
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encircles entrace to 1 capillary. constrict. shuts off blood flow through their respect cap&diverts blood to tiss or organs elsew |
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cartoid sinuses |
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baroreceptors(press sensors) respond to changes in bp- wall of intern carotid artery- monitor bp |
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carotid bodies |
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oval recept-3x5mm-sensory fivers of vagus&gloss nerves-monitor blood CO2 O2 and PH |
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aortic bodies |
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one to three chemorecptors located in oartic arch near arteries in head & arms- monitor blood comp |
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blood capillaries |
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composed of only an endothelium & bment memb-walls .2-.4 mm |
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where are capillaries scarce? |
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tendons & ligaments & absent from epithelia, cornea, and lens, and most cartilage |
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3 types of capillaries |
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continuous, fenestrated, sinusoids |
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continuous capillaries |
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occur in most tissues- enothelial cells-tight juncts-uninterrupted tube- exhibit pericytes |
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fenestrated capillaries |
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filtration pores-allow for rapid passage of molecs butretain blood cells & platelets in bstream-kidnesys,endoglands,small I, choroid plex |
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sinusoids |
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irregular, highly porous blood spaces in such tissues as liver, spleen& b. marrow-twisted-conform to shape of surround tiss-gaps |
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pericytes |
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lie external to endothelium- contractile proteins- diff into endothelial & smooth mesc cells & thus contrib to vess growth & repair |
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capillary beds |
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capillaries organized into these networks- 10 to 100 caps/metarteriole. they continue > thoroughfare channel |
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thoroughfare channel |
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leads directly to a venule |
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capacitance vessles |
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a.k.a veins- thin walled & flaccid-exp easily to accom an inc vol of blood- greater capactiy for blood contain. than arter. steady flow of blood |
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smaller veins are calledexih |
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tributaries |
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postcapillary venules |
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smallest veins-exch fluid with the tissues- very porous |
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muscular venules |
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receive blood from postcap venules- up to 1mm in diam- have tunica media of 1 or 2 layers of smooth musc & a thin tunica ext |
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medium veins |
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up to 10mm-most veins w. individ names-exhibit infoldings of tunica interna to meet in midd of lumen forming venous valves |
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varicose veins |
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failure of venous valves- ppl who stand long time-obesity and preg can promote- press on large veins & obstruct drainage to legs. |
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varicose veins of anal canal |
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hemorrhoids |
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venous sinuses |
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veins w. esp thin walls, large lumens, and no smooth musc- ex. coronary sinus of heart- NOT capable of vasomotion |
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large veins |
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greater than 10mm- venae cavae, pulmon veins, internal jug, renal veins |
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