Cardiovascular System Flashcards
How many miles of blood vessels
60,000
Cvs role in homeostasis
Transport and deliver blood. Carry nutrients to tissue. Carry waste away.
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.
arterioles
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
METARTERIOLE
TAPERS toward capillary junction. distal most muscle cell which regulate resistance to blood flow
capillaries
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
sinusoids
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
venules
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
veins
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
