Chapter 18
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| arteries | carry blood away from heart, they branch into vessels of progressively smaller diameter that supply most tissues in body with blood
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| pulmonary circuit | transports blood between heart and lungs
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| systemic circuit | transports blood between heart and rest of body
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| capillaries | exchange system of musculature; small-diameter vessels that form branching networks called capillary beds; gases, nutrients, wastes,other molecules are exchanged between tissue cells and blood through capillary walls which are only one cell layer thick
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| veins | drain blood into capillary beds and return it to hear; follow opposite pattern of arteries; small veins merge with other veins to become progressively large vessels as they progress towards the heart
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| tunica intima | single layer of subendothelial connective tissue and a layer of elastic fibers (internal elastic lamina), giving ability to stretch with increased pressure and recoil back; provides smooth surface for minimal friction or turbulance
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| tunica media | composed of two layers: smooth muscle cells and elastic fibers called external elastic lamina; smooth muscle cells control diameter of blood vessel and amount of blood that flows to organs
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| tunica externa | composed of dense irregular collagenous connective tissue that supports blood vessel and prevents it from overstretching
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| vasa vasorum | tiny vessels supplying tunica media and tunica externa (need their own blood supply); supply oxygen and nutrients to outer layers of larger blood vessels, whose cells are too faraway from lumen to recieve oxygen and nutrients by diffusion alone
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| 2 notable differences between an artery wall and a vein wall | 1. most arteries have thicker tunica media than veins (reflects arteries role in controlling blood pressure and blood blow)
2. internal and eternal elastic lamina are more extensive in arteries (reflects fact that arteries are under higher pressure)
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| elastic (conducting) arteries | largest diameter; include aorta, brachiocephalic, subclavian, carotid; nearest to heart and therefore highest pressure of any vessels
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| baroreceptors | pressure receptors
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| chemoreceptors | detect blood oxygen, carbon dioxide, and hydrogen ion concentrations
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| muscular arteries (distributing arteries) | intermediate in diameter; well-developed tunica media composed of smooth muscle cells; include most named arteries that supply organs
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| arterioles | smallest arteries; contain all 3 layers but layers are extremely thin, and tunica media contains only1-3 layers of smooth muscle
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| metarterioles | smallest arterioles; directly feed capillary beds in most tissues; contain precapillary sphincters that encircle metarteriole-capillary junctions
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| list 4 differences between arteries and veins that allow veins to collapse | veins typically have much thinner walls, fewer elastic fibers, less smooth muscle, and larger lumens that arteries
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| What percent of total blood in the body is located in the veins? This allows veins to function as__________. | 70%, blood resevoirs
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| Smallest veins? They drain blood from capillary beds through __________. | venules; postcapillary pvenules
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| postcapillary venules | extensions of tunica intima that prevent blood from flowing backward; numerous in veins of legs, where blood flow opposed to gravity
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| atherosclerosis | leading cause of death in developed world; characterized by formation of atheroclerotic plaques: buildup of lipids, cholesterol, calcium salts, and cellular debris within tunica intima of arteries; form in response to injury
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| cause and effect of atherosclerosis | plaques tend to form in regions where blood undergoes sudden changes in velocity and direction of flow, such as branching points or where vessels curve, clot may form in vessels next to plaque and obstruct blood flow
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| vascular anastomoses | connect via pathways called collateral vessels
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| arterial anastomoses | found in heart and brain, as well as around joints; new ones can be formed when blood flow through an artery is insufficient to meet tissue's metabolic needs called angiogenesis
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| venous anastomosis | most common type; neighboring veins are connected by small collaterals; smaller veins are often so interconnected that they form complex, weblike patterns
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| arteriovenous anastomosis | artery empties directly into a vein without passing through a capillary bed
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| hemodynamics | physiology of blood flow in the cardiovascular system, basic concepts related to blood flow
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| blood pressure | outward force that blood exerts on walls of blood vessels; measured in mm Hg; highest in large systemic arteries and lowest in large systemic veins
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| blood flow | volume of blood that flows per minute; cardiac output averages 5-6 L/min.; directly proportional to the blood pressure gradient and inversely proportional to resistance
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| peripheral resistance | any factor that hinders blood flow through vasculature; vessels near the heart contribute little to overall resistance; it is greater furthest from the heart; determined by R=1/r^4
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| radius of vessel | varies inversely with resistance; as radius increases resistance decreases
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| blood viscosity | inherent resistance that all liquids have to flow
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| blood vessel length | the longer the blood vessel, the greater the resistance; more pressure is needed to propel blood through a long vessel than a short one
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| obstruction | blood clot, fatty plaque
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| laminar | perfect flow, moves in layers, blood is central (faster in middle, slower near walls)
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| turbulent | when there is an obstruction, blood flow spins/ moves around obstruction; can cause blood clots
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| vascular compliance | onset by ability of vessels to stretch
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| 15; 95 | Blood pressure averages __mm Hg in the pulmonary circuit and __,, Hg in the systemic circuit.
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| systemic arterial pressure | describe BP from aorta to muscular arteries; highest in aorta and elastic arteries and declines slightly as it spreads throughout the muscular arteries
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| systemic capillary pressure; 35; 15 | pressure at arteriolar end of a capillary bed __ mm Hg while at venular end of capillary bed of capillary bed, pressure has decreased to about __ mm Hg
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| Mean arteriolar pressure (MAP) | average pressure in systemic arteries during an entire cardiac cycle; generally measures about 95 mm Hg
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| systolic pressure (SP) | pressure generated by ventricular contraction; averages about 120mm Hg at rest in in aorta, 110 in brachial arteries
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| Diastole pressure (DP) | pressure generated by ventricular relaxation; average 80mm Hg at rest in aorta, 70 in brachial arteries
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| Pulse Pressure (PP) | difference between systolic and diastolic pressure
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| Instruments used to measure arterial blood pressure | Sphygmomanometer on arm, stethoscope
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| formulas for MAP and PP | MAP=diastolic+1/3 (systolic-diastolic)
PP=systolic- diastolic
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| 3 ways rate of venous return is increased | 1. venous valves prevent backflow 2. smooth muscle in vein walls can contract under sympathetic nervous system simulation 3. skeletal muscle pumps squeeze blood in veins towards heart
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| 1 other way venous return is increased | respiratory pumps- inspiration, high pressure in abdominopelvic pushes blood in abdominal veins upward, and low pressure in thoracic cavity allows veins to expand. expiration- abdominal veins expand and fill with blood while thoracic veins are squeezed
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| short-term maintenance of blood pressure | due to nervous system controls and certain hormones of the endocrine system and by the adjustment of resistance and cardiac output
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| nervous system maintenance of blood pressure | control of homeostasis is the autonomic nervous system via 2 divisions: sympathetic and parasympathetic
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| sympathetic effects on blood prpessure | sympathetic axons release norepinephrine and epinephrine onto cardiac and smooth muscle cells of blood vessels to produce 2 changes (both increase BP): increase HR and contractibility (inc. CO), vasoconstriction on all, but mainly arterioles (inc. PR)
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| parasympathetic effects on blood pressure | parasympathetic axons via vagus nerves, release acetylcholine onto pacemaker cells of sinoatrial and atriventricular nodes; decreases BP by slowing heart rate and decreasing CO
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| the baroreceptor reflex | negative feedback loop that responds to increases or decreases in BP
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| baroreceptor reflex: stimulus | blood pressure increases above normal range
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| baroreceptor reflex: receptor | baroreceptors in the carotid sinus detect the increased pressure and fire action potentials in a faster rate
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| baroreceptor reflex: control center | the impulses travel to the medulla of the brainstem for integration
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| barorececptor reflex: effector/ response | parasympathetic neurons in the medulla oblongata inhibit sympathetic activity, blocking vasodilation and decreased HR, lowering CO
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| baroreceptor reflex: homeostatic range | blood pressure decreases, and feedback decreases response from the medulla
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| valsalva maneuver | raises the pressure in the thoracic cavity and reduces the return of venous blood to the heart, causing a drop in BP. Baroreceptor reflex is triggered, increasing HR
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| Peripheral Chemoreceptor Stimulation | Play roles in regulation of breathing, but they also affect blood pressure; receptors respond mostly to level of oxygen in blood; decrease O2 levels activate Sympathetic NS increasing HR and BP (vasoconstriction)
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| Central Chemoreceptor Stimulation | Respond to decreases in pH in brain; increases activity of sympathetic neurons; result in vasoconstriction and increase in blood pressure
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| Hormones that control cardiac output | epinephrine, norepinephrine, thyroid hormone
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| Hormones that control resistance: | Epi and Norepi-released from adrenal medulla cause vasoconstriction, inc. peripheral resistance, which elevates blood pressure;angiotensin-II- is a powerful vasoconstrictor;atrial natriuretic peptide (ANP)-causes a mild dec. in peripheral resistance
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| Long-Term Maintenance of Blood Pressure by the Endocrine and Urinary Systems | Control blood pressure by increasing or decreasing the amount of body water lost as urine by kidneys, which affects blood volume.
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| Urinary system controls blood volume with these responses: if BP increases | If BP inc: more water flows through kidney tubules; water is then lost from body as urine, and BV and BP dec.
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| Urinary system controls blood volume with these responses: if BP decreases | If BP dec: less water flows through kidney tubules; time to reclaim water and return it to blood; results in dec. urine prod. and inc. in BV and BP
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| hypertension | BP that is too high; systolic pressure > than 140 mm Hg and/or a diastolic pressure > than 90 mm Hg
Essential (primary)(95%)- cause is unknown but genetics plays a role
Secondary- cause can be determined
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| pre-hypertension | systolic 120-139 mm Hg, diastolic 80-99 mm Hg
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| hypotension | low blood pressure; systolic pressure lower than 90 mm Hg and/or a diastolic pressure lower than 60 mm Hg
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| tissue prefusion | blood flow to a tissue through a capillary bed
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| capillary structure | simple squamous epithelium, endothelium, tunica intima; basal lamina secreted by endothelial cells
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| pericytes | cells found around some capillaries; have contractile filaments and appear to control blood through capillaries
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| capillary exchange | movement of nutrients, gases, ions, and wastes across the wall and travel between the blood in the capillary and the tissue cells
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| intercellular gaps and fenestrations | diffusion and osmosis of water and water-soluble materials such as monosaccharides and amino acids
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| simple diffusion | lipid-soluble materials diffuse through membranes of epithelial cells; steroids, gases, fatty acids
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| transcytosis | large water-soluble compounds brought into cell by endocytosis and released by exocytosis to interstitial fluid
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| continuous capillaries | endothelial cells joined by tight junctions, least “leaky”—permit a narrow range of substances to cross the capillary walls (skin, most nervous and connective tissue, muscle tissue)
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| fenestrated capillaries | contains fenestrations in the endothelial cells; moderately leaky—allow large volumes of fluid and larger molecules to cross capillary walls (kidneys, endocrine glands, small intestine)
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| sinusoidal capillaries | discontinuous sheet of endothelium, irregular basal lamina, very large pores; leakiest—allow larger substances such as cells to cross the capillary walls (liver, lymphoid organs, bone marrow, spleen)
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| microcirculation | involves true capillaries, where materials are exchanged, and a small, central vessel
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| metarteriole- capillary beds | central vessel of proximal end
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| precapillary sphincters-capillary beds | controls amount of blood flowing into capillaries
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| thouroughfare channel- capillary beds | central vessel of distal end, movement of blood in one direction
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| Local Regulation of Tissue Perfusion | Autoregulation or self-regulation ensures that the correct amount of blood is delivered to match a tissue’s level of activity
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| autoregulatory control: myogenic mechanism | due to smooth muscle cells of arterioles; slows blood flow by increasing resistance (constricts) when arteriolar pressure rises; speeds up blood flow by decreasing resistance (dilates) when arteriolar pressure lowers
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| autoregulatory control: metabolic controls | mediated by chemical in intestinal fluid; high metabolic tissue with low )2 and high CO2 and [H+], dilate to increase blood flow; dilate to increase blood blow; tissue with low metabolic needs will constrict to decrease blood flow into capillary bed
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| heart- tissue perfusion; 5% | __% of CO; heart tissue prefusion decreases during systole; main local autoregulatory mechanism of metabolic control is concentration of oxygen; oxygen level triggers production of chemicals called vasodilators
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| brain-tissue perfusion;15% | % of CO; extremely intolerant of ischemia; sudden decrease in tissue prefusion to brain will result in loss of consciousness within seconds; autoregulation maintains constant blood flow; astrocytes produce vasodilators
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| skeletal muscle- tissue prefusion | blood flow increases during exercise; metabolic control due to increasing metabolic needs
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| skin- tissue perfusion | largest organ in the body; autoregulation due to temperature via sympathetic nervous system; vasoconstriction to conserve heat or vasodilation to release heat
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| filtration | the movement of a fluid by a force such as pressure or gravity (moves water across capillaries)
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| hydrostatic pressure | force that a fluid exerts on the wall of its container. equal to BP. Fluid flows through from an area of higher hydrostatic pressure to an area of lower hydrostatic pressure; passively filtrates; 35 mm Hg at arteriolar end, 15 mm Hg venular end
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| osmotic pressure | 25 mm Hg; created by large proteins in blood, especially protein albumin because proteins are too large to leave capillary, so osmotic pressure remains consistent throughout capillary’s length and osmotic pressure is 3mm Hg in interstitial fluid
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| colloid osmotic pressure (COP) | oncotic pressure; difference in osmotic pressure that creates as osmotic pressure gradient
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| equation to find capillary net filtration pressure (NFP) | NFP = (HPcap – HPif) - (OPcap – OPif)
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| arteriolar; 13 | At the capillary’s __________ end, the NFP is __ mm Hg. This force drives water out of the capillary by filtration because hydrostatic pressure is greater at this end
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| venular; -7 | At the capillary’s __________ end, the NFP is __ mm Hg. NFP is a negative number, which means that water flows into the capillary. Colloid osmotic pressure is greater and water is absorbed into the capillary by osmosis.
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| edema | condition characterized by an excessive amount of water in the interstitial fluid
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| 2 common causes of edema | Inc. in capillary hydrostatic pressure gradient due to hypertension, dec. in colloid osmotic pressure due to liver disease, cancer, or starvation, among other disorders
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| ascites | accumulation of fluid in abdomen
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| peripheral edema | edema found in hands and feet where hydrostatic pressure gradient is already slightly higher due to effects of gravity
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| 2 main causes of cerebrovascular accident (stroke) (4th most common cause of death in US) | blockage of one of brain’s arteries due to a clot; (2) loss of blood, or hemorrhage, due to a ruptured cerebral artery
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| risk factors of stroke | hypertension, atherosclerosis (particularly in carotid arteries), diabetes mellitus, cigarette smoking, hypercholesterolemia, and a cardiac dysrhythmia called arterial fibrillation
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