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Flashcards in Cardiovascular System Deck (30):

Cvs role in homeostasis

Transport and deliver blood. Carry nutrients to tissue. Carry waste away.


How many miles of blood vessels



5 types of blood vessels

Arteries arterioles capillaries venues veins


Three layers of a blood vessel

Intima-epithelial lining media- smooth muscle externa- connective outer covering


Tunica intima

Direct contact with blood, continuous with endocardial lining, secretes chemicals influencing contractile state of vessel, facilitates efficient blood flow by reducing friction


Parts of tunica intima

Deep to endothelium is the basement membrane which is for strength and resilience made of collagen fibers and outermost layer is internal elastic lamina which is thin elasticity with windows for diffusion


Tunica Media

Muscular and connective layer.greatest variation between vessels. Regulates diameter of lumen. This in turn regulates blood flow through constriction and dialation which affects blood pressure. Also produces elastic fibere which allow vessel to stretch and recoil.


external elastic lamina

network of elastic part of tunica media. separates tunica media from tunic a externa


tunica externa

outer covering of blood vessel which consist of collagen and elastic fibers. Contains nerves tiny blood vessels to supply tissues of the vessel (vasa vasorum- vessel to vessel) also anchors vessel to surrounding tissue


elastic arteries

largest arteries which include garden hose size aorta and pulmonary trunk to finger size branches of aorta. well defined internal and external elastic lamina. function to propel blood onward while ventricles relax, by elastic recoil which moves blood along. Also known as conducting arteries


muscular arteries

medium sized arteries. tunica media contains more smooth muscle and less elastic fibers. greater ability to vasoconstrict/dialate. well defined internal elastic lamina but thin external elastic lamina.


muscular arteries size

range from pencil sized (femoral and axillary) to as little as .5 mm. vessel wall comprises 25% of total vessel diameter. also known as distributing arteries. tunica externa is often thicker than tunica media and contains fibroblasts collagen fibers and elastic fibers longitudinally which prevents shortening or retraction of vessel when cut


muscular artery function

cannot recoil to help propel blood like elastic arteries. contract and maintain a state of partial contraction (vascular tone). important in maintaining vessel pressure and efficient blood flow.



small arteries which regulate flow into capillaries 15-300 micrometers and wall thickness is 1/2 of total vessel diameter. thin tunica interna, thin fenestrated elastic lamina which disappears at terminal end. tunica media is 1-2 layers of smooth muscle with circular orientation. tunica externa contains sympathetic nerves which alter diameter of arterioles also known as resistance vessels which affect BP



TAPERS toward capillary junction. distal most muscle cell which regulate resistance to blood flow



smallest blood vessels. diameter of 5-10 microns. lack tunica media and externa. composed of single layer of endothelial cells and a basement membrane rbc have diameter of 8 microns so they have to fold to squeeze through. lots of SA which makes contact wit all cells. called exchange vessels capillary network varies with metabolic activity


precapillary sphincters

when relaxed blood flows, when contracted BF stops. flow is intermittent due to alternating contraction and relaxation of smooth muscle of metarteriole. vasomotion partly from chemicals released by endothelial cells


thoroughfare channel

direct route from arteriole to venule by passing capillaries.
diatal end of vessel has no smooth muscle


continuous capillaries

continuous tubes interrupted only by intercellular clefts


fenestrated capillaries

contain fenestration (70-100 nm) found in kidneys, villi of small intestines, and choroid plexuses



wider and winding than other caps. large fenestrations. incomplete or absent basement membrane. large intracellular clefts which allow proteins and new RBC to pass through



thin walls that do not maintain shape


post cap venules

drain cap blood and begin to return to heart (10-50 micron) very porous significant site of nutrients and waste wbc emigration


muscular venules

1-2 layer of smooth muscle prevent exchange of nutrients and waste. thin walls allow for expansion and serve as reservoir



not much structural change like artery. thin walls. (.5mm -3cm) same layers as arteries but thickness differs. interna and media is thinner but externa is thicker. no internal or elastic lamina


vein characteristics cont.

adaptable to volume but not designed to withstand high pressure. lumen is flattened in cross section BP IS LOWER THAN ARTERIES. contain valves from tunica interna. project into lumen and point toward heart which prevents backflow


vascular sinus

wein with thin endothelial wall no smooth muscle. dense connective tissue replaces tunica media and externa for support.


anastomotic veins

connected like a latter


blood distribution

veins and venules 64%. arteries and arterioles 13%. capillaries 7%. pulmonary blood vessels 9%. heart 7%.


blood reservoirs

liver, spleen, veins, and venules can hold diverted blood if needed from venoconstriction