A&P.CardioV.ch21
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| ventricle to elastic arteries to muscular arteries to arterioles then to capillaries | path of blood FROM the heart
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| from capillaries-blood flows into venous system | venules; then small veins or medium or large veins
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| blood vessels - internal lining | endothelium - simple squamous epithelial cells - continuous with the dnocardium of the heart
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| capillaries (3) | continuous capillaries; fenestrated or sinusoidal
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| continuous | continuous capillaries - NO GAPs between endothelial cells; less permeable to large molecules - occur in muscle, nervous tissue & many other
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| fenestrated capillaries | fenestrae "windows" - have no cytoplasm - the plasma membran is thin-a porous diaphragm (thiner than normal plasma membrane) - some capillaries have no diaphrabm - highly permeable such as in intestinal villi, ciliary process of the ey, choroid plexuses o
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| sinusoidal capillaries | larger in diameter than; basement membrans is less prominent or no basement membrane-they have fenestrae which are larger than fenestrated capillaries and have GAPS -occur in ENDOCRINE glands, where large molecules cross their walls
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| sinusoids | large-diameter siusoidal capillareis - little or no basement membrane; structured for large molecules and even cells can move across their walls- found in liver and the bone marrow
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| venous sinuses | similar in structure to sinusoids; but are even larger; found in the spleen - they have large gaps between the endothelial cells in their walls
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| can red blood cells pass through capillaries? | no
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| Layers or tunics of blood vessel wall (3) | intima, media and adventitia
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| Large arteries have a lot of _______ and little ______________ | large arteries have a lot ofelastic tissue and little smooth muscle
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| as arteries become smaller | they have LESS elastic tissue and more smooth muscle
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| Walls of veins are | THINNER and LESS ELASTIC, with not a lot of smooth muscle
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| Veins closest to the heart are | WIDER and walls become THICKER
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| types of arteries (3) | 1.) elastic; 2) muscular 3) arterioles
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| capillaries | most of the exchange that occurs between the blood and interstitial spaces occurs across the walls of capillaries
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| capillaries | 1) their walls are thinnest; 2.) blood flows through them slowly and most of the exchange that occurs between the blood and interstitial spaces occurs across the walls of capillaries
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| what type of artery is most numerous? | capillaries
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| types of capillaries (3) | continuous; fenestrated and sinusoidal
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| continuous capillaries | NO
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| fenestrated capillaries | means "window" or "pore"-allow for easy passage of material - found in intestinal villi, glomeruli of the kidney
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| sinusoids are common in the (2) | liver and the bone marrow. Macrophages are closely associated with the endothelial cells of the liver sinusoids
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| venous sineuses | similar to sinusoidal capillaries; but even larger in diameter-occur in the spleen. LARGE GAPS between the endothelial cells that make up their walls.
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| substances cross capillary walls by | DIFFUSION - through the endothelial cells, through fenestrae, or between endothelial cells
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| what diffuses through plasma membrane? | oxygen & carbon dioxide (which are lipid-soluble) and samlll water-soluble molecules diffuse through the plasma membren.
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| what diffuses through fenestrae? | larger water-soluble substances (need examples)
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| capillary network (general | Arterioles (have muscles) provide blood to capillaries (move by diffusion)
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| path of capillaries | from arterioles to the metarteriole through thoroughfare channel past pprecapillary sphincter through the arterial capillaries through the venous capillaries through to the venule, which then becomes a vein
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| precapillary sphincter | small areas of smooth muscles - regulate flow through capillaries
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| capillary networks in the skin | have many more thoroughfare channels (than in cardiac or skeletal muscle) because they function in thermoregulation. Heat loss from blood flow occurs
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| in muscle, the main job of capillaries is | nutrient and waste product exchange
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| tunics (3) | tunica intima; tunica media; tunica adventitia (also called tunica externa)
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| tunica intima | Innermost layer - in contact with blood - made of simple squamous cells with no gaps (very smooth to allow blood flow), lamina propria; thin connective tissue in basement membrane
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| what is lamina propria? | thin layer of connective tissue in tunica intima
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| lamina | sheets - remember "sheets" lamallae in bone tissue
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| elastic arteries | contain elastic tissue - rebound after systolic & diastolic in heart-more elastic tissue than muscle -
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| tunica intima | endothelium cells, a delicate basement membrane, and a thin layer of connective tissue called the lamina propria
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| tunica media | smooth muscle cells arranged circularly around the blood vessel - these control blood flow
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| tunica media has two ways to control floow of blood | vasodilation or vasoconstriction
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| vasodilation | dilate L. dilato "to spread out" think of the eye opening
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| vasoconstriction | to make blood vessel smaller in diameter; slows flow of blood
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| external elastic membrane | separate the tunica media from the tunica adventitia - it is at the outer border of the muscle walls
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| tunica adventita | Connective tissue - remember that blood vessels are continuous with the connective tissue with the heart
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| how are blood vessels differentiated? | the predominant layer-blood vessels gradually become larger
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| elastic (conducting) artery | Largest arteries in body; pressure is high; fluctuates between systolic and diastolic values. more elastic tissue than muscle (duh!)
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| in elastic arteries, the _________ is relatively thick | the tunica intima is relatively thick-the elastic fibers of the internal & external elastic membranes merge and are not recognizable as distinct layers
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| muscular arteries also called medium arteries | unlike the elastic arteries nearest the heart, the tunica media contains muscle to control flow of blood
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| muscular arteries are also called | distributing arteries because they use vasodilation or vasoconstriction to regulate flow of blood
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| smaller muscular arteries | have 3-4 layers of smooth muscle in their tunica media - essentially the same structure as "medium" muscular arteries
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| arterioles | smallest arteries with 3 differentiated tunics - 1-2 layers of smooth muscle cells in tunica media; capable of vasoconstriction & vasodilation
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| venules and small veins | venules do NOT have 3 layers - drain capillary network - have some nutrient exchange but was vessesl increase they become small veins
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| do venules have endothelial cells? | yes, all blood vessels are lined with endothelial cells
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| endothelium | layer of flat cells that line the blood vessels, lymphatic vessels and the heart
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| small veins | smooth muscle cells form a continuous later; the tunica adventita is composed of collagenous connective tissue
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| what is difference between venules and small veins? | venules do NOT have complete smooth muscle layer (they have basement cells & endothelial cells) but NOT muscle layer
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| Medium & large veins | Predominant layer is tunica adventitia - which is composed of collagenous connective tissue
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| do medium & large veins have smooth muscle? | yes, they have all three tunics, but the tunica media is thin & composed of a thin layer of smooth muscle cells
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| valves | VEINS have VALVES - valves are folds in the tunica intima which overlap & prevent backflow of blood- many valves are present in medium veins, and there are more valves at lower extremeties than in upper extremities
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| vasa vasorum | for arteries and veins larger than 2mm in diameters, the blood flowing through them can't reach outer layers; therefore small blood vessels penatrate the exterior of the vessel to form a capillary network
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| vasa vasorum | supplies nutrients to all the tunics (not getting it from blood in circulation)
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| valves | in veins over 2 mm in diameter - remember 2 "v's" 2mm's
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| arteriovenous anastomoses - allow blood to flow from arteriols to small veins without passing through capillaries | present in hands, feet and nail beds- function in temperature regulation
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| pathologic arteriovenous anastomoses | can result from injury or tumors-cause direct flow of blood from arteries to veins & can lead to heart failure because too much blood is returned to the heart
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| portal veins | begin in a primary capillary network, travel, then end in a secondary capillary network - NO PUMPING mechanism -
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| how many systems of portal veins? | in humans, there are two - the hepatic portal veins (carry blood from the capillaries in the gastroinetstinal tract to sinusoids in liver and in brain
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| sinusoids are | dilated capillaries within liver
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| nerve supply to blood vessels | most blood vessels have unmyelinated sympathetic nerve fibers; these form "plexi" an organization of nerve fibers in tunica adventitia - there are frequent gap junctions, which mean that stimulation of a few smooth muscle cless results in constriction of
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| parasympathetic nerve | in blood vessels results in vasodilation - these are found in penis & clitoris
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| sympathetic nerve stimulation | in most blood vessels results in vasoconstriction
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| myelinated nerve fibers in blood cells | some blood vessels have myelinated sensory neurons - which function as baroreceptors - think barometer - they monitor blood pressure rise & fall
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| aging of arteries - arteriosclerosis | general term for degenerative changes in arteries making them LESS ELASTIC
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| sclerosis | g sklerosis "hardness"
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| atherosclerosis | deposition of material in walls of arteries to form plaques; first it is fatlike substance containing cholesteraol; then can become dense connective tissue and calcium deposits
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| arteriosclerosis | the tunica intima thickens and the tunica media becomes less elastic due to chemical change in elastic fibers-extends into artery wall & slow the flow of blood
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| arteriosclerosis caused by | 1.) aging or wearing; 2. may or may not be pathologic process 3. may result from inflammation from autoimmune disease
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| dynamics of blood flow | like water flowing through pipes, there is an interrelationship between pressure, flow, resistance and the control mechanisms that regulate blood pressure and blood flow
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| types of blood flow: | laminar and turbulent
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| laminar flow | remember "laminae" sheets - blood flow behaves as if it were composed of a large number of concentric layers, ie. like lava pouring through a tube
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| laminar flow-where is flow fastest? | innermost layers - they slip over out layers (like lava) -
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| where is flow slowest? | layer nearest wall of the tube because it moaves against the stationary wall
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| turbulent blood flow | when blood flow is interrupted, it produces a sound on the stethoscope
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| when does turbulent blood flow occur? | 1. when blood flow interrupted; 2. rate of flow exceeds critical velocity; 3. when fluid passes a constriction, sharp turn or rough surface
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| what does turbulent blood flow mean? | turbulent blood flow occurs primarily in heart & to a lesser extent where artereies branch BUT sounds caused by turbulent blood flow in arteries are not normal & usually indicate blood vessel is constricted
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| what can occur when turbulent blood flow in abnormally constricted arteries? | the possibility of a thromboses will develop in are of turbulent flow
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| blood pressure | measure of force exerted by blood against blood vessel wall
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| methods of measuring | directly (using cannula) or indirectly using auscultatory method
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| cannula or tube measure of blood pressure | insert cannula into blood vessl and connect to a manometer or electronic pressure transducer - this will detect rapid changes to pressur
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| auscultatory | l "to listen to"
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| sphygmomanometer | instrument for measuring arterial blood pressure indirectly, consisting of an inflatable cuff, inflating bulb, and a gauge showing the blood pressure sphygom "pulse" plus mano "thin or scanty" plus "metro" measure
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| korotkoff sounds | turbulent blood flow & its vibrations create sounds which can be heard & measured
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| systolic pressure - korotkoff sounds | when the blood pressure cuff is deflated, the first sound represents the systolic pressure
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| diastolic pressure - korotkoff sounds | when cuff continues to deflate, korotkoff sounds change tone--when they disappear, this means that laminar flow is reestablished - this is the diastolic pressure - this is the diastolic pressure
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| blood flow | rate of blood flow in a vessel can be written as an equation: flow equals pressure in point 1 minus pressure in point 2 divided by rate -
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| poiseuille's law | states that a small change in the radius of a blood vessel dramatically changes resistant in flow -this is very important when arteries are clogged
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| viscosity of blood - does it affect flow? | measure of resistance of a liquid to flow - blood is about 3x more viscous than distilled water, meaning that 3x as much pressure is required to force whoel blood to flow through a given tube at the same rate as water
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| hematocrit | this influences the viscosity of blood - normal blood with viscosity of 45% flows OK, but blood with a very high hematocrit of 65% has a viscosity 7 or 8 times that of water
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| do plasma proteins affect viscosity? | no, they only have minor effect
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| poiseuille's law | pi times (p1 -p2) times RADIUS to the 4th POWER divided by 8 times VISCOSITY time length (of the blood vessel)
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| what causes hemotocrit to rise? | dehydration or uncontrolled production of erythrocytes
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| critical closing pressure | if blood vessel pressure falls too low, the vessel will collapse & blood flow stops - under conditions of shock, blood pressure can decrease below critical closing pressure
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| Laplace's law | states that the force that stretches the vascular wall is proportional to the diameter of the vessel times the blood pressure or F(force) = D (vessel diamter) x P(pressure)
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| when arterial wall has a bulge | the wall is weakened & it bulges out- making the diameter greater; therefore, the force applied to the weakened part is greater than at other point along the blood vessel-greater force causes the bulge to get bigger - then it can rupture
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| aneurysms | bulge in the wall of weakened blood vessel - these can rupture
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| vascular compliance | 1. tendency for blood vessel volume to increase as blood pressure increases 2. the more easily the bessel wall stretches, the greater its compliance
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| what are more compliant? | veins are more compliant-venous system has 24x greater increase in volume; therefore, venous system acts as blood reservoir
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| physiology of systemic circulation | describes the anatomy of the ciculatory system, blood flow & regulatory mechanisms
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| how much of total blood volume is in vessels? | about 84% is in systemic blood vessels-of that total, 64% is in veins (where most blood is "stored"); 15% in arteries and 5% in capillaries
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| which blood vessel has fastest velocity | the arteries
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| which blood vessel has largest cross-sectional area? | capillaries -but remember that the velocity of blood flow is low in the capillaries
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| how is cross-sectional area determined? | measure - aorta has a cross-sectional area of 5 sq. centimeters; however, there is only one aorta. the cross-sectional areas of the thousands of capillaries is much greater
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| pulse pressure | the difference between the systolic and diastolic pressures
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| blood pressure falls | as blood moves from aorta to capillaries
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| pulse pressure formula | pulse pressure = systolic pressure MINUS diastolic pressure; normal pressure is 120/80; therefore 120-80=40 - normal pulse pressure is 40
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| where is resistance to blood flow the greatest? | in arterioles - and also in capillaries - which are narrow & only one RBC can flow through at a time
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| resistance to blood flow is low | in the veins, because of the relatively large diameter
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| pulse pressure is influenced by | 1. stroke volume of the heart and 2. vascular compliance [remember stroke volume equals volume of blood pumped during each heartbeat, which is equal to end-diastolic volume minus end-systolic volume
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| what happens to pulse pressure in older people? | arteries in older people become less elastic {less compliant } or arteriosclerotic - the resulting decrease in compliance cause the pressure in the aorta to rise more rapidly and to a greater degree in systole and to fall more rapidly to its diastolic val
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| for a given stroke volume, what happens when vascular compliance decreases? | systolic pressure and pulse pressure are higher as vascular compliance decreases
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| what happens with pulse pressure when a young, fit runner runs three miles? | stroke volume increases, and, as a consequence, puls pressure also increase. After running, the pulse pressure gradually returns to its resting value as the stroke volume of the heart decreases.
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| what is a palpable pulse? |
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