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Anatomy Chapter 20
| Question | Answer |
|---|---|
| which blood vessel carries blood away from the heart? | arteries |
| which blood vessel carry blood back to the heart? | veins |
| which blood vessel connects the smallest arteries to veins? | capillaries |
| arteries look perfectly _____ under a microscope and have a _____ lumen and ______ vessel walls | round; smaller; thicker |
| veins have _____ lumen and _____ vessels walls | larger; thinner |
| what is the tunic interna? | internal layer; lines the blood vessel and is exposed to blood |
| what is the tunica interna made of? what does it do? | made of simple squamous epithelium overlying a basement membrane and a sparse layer of loose connective tissue; acts as a selectively permeable barrier and secretes chemicals for vasomotion ex: histamine |
| the endothelium of the vessel wall and clotting? | endothelium normally repels blood cells and platelets that may adhere for clotting; when tissue is inflamed it produces cell adhesion molecules that induce leukocytes to adhere to surface (clot) |
| what are the three layers of the blood vessel? | 1. tunica interna (internal layer/touches blood) 2. tunic media (middle layer/smooth muscle) 3. tunica externa (outermost layer/anchors/passageways) |
| what is the tunica media? what does it consist of? | the middle layer of the blood vessels; made of smooth muscle, collagen, and elastic tissue for CONTRACTION; |
| what does the tunica media do? | strengthens vessels and prevents blood pressure from rupturing them and does this by vasomotion |
| vasomotion | changes in diameter of the blood vessel brought about by smooth muscle; vasoconstriction and vasodilation; EX: tunica media |
| what is the tunica externa? what does it consist of? | outermost layer; made of loose connective tissue that often merges with neighboring blood vessels, nerves, or other organs; |
| what does the tunica externa do? | anchors the vessel and provides passage for small nerves, lymph vessels; big part is vasa vasorum |
| what is another name for the tunica externa? | tunica adventitia |
| what is vasa vasorum? | small vessels that supply blood to at least the outer half of the larger vessels; gives nutrients and takes away waste for large vessels; |
| what are arteries sometimes called? and why? | resistance vessels because they have a relatively strong, resilient tissue structure that resists high blood pressure; withstand large changes in pressure |
| what are the two types of arteries? | conducting and distributing |
| conducting arteries | elastic or large arteries; biggest; between interna & media layers they have a layer called internal elastic lamina made up of elastic tissue; |
| what are some examples of conducting arteries? | aorta, common carotid, subclavian, pulmonary trunk, and common iliac arteries |
| what do conducting arteries do? | expand during systole, recoil during diastole which lessens fluctuations in blood pressure; withstand large changes in blood pressure |
| distributing arteries | muscular or medium arteries; smooth muscle layer constitutes 3/4s of wall thickness |
| what are some examples of distributing arteries? | brachial, femoral, renal and splenic arteries |
| what do distributing arteries do? | distribute blood to specific organs |
| blood flow through vessels | Conducting Arteries -> Distributing Arteries -> Arteriole -> Capillary -> Venule -> Medium Vein -> Large Vein |
| arterioles | small resistance arteries; have thicker tunica media in proportion to their lumen than large arteries and very little tunica media |
| what do arterioles do? | control the amount of blood to various organs |
| metarterioles | short vessels that link arterioles to capillaries; |
| what are precapillary sphincters? where do they occur? | they constrict to reduce or shut of blood flow through capillaries; help divert blood to other tissues; occur in metarteriole before capillary |
| what is an aneurysm? | weak point in an artery or the heart wall; forms a thin walled bulging sac that pulsates with each heartbeat ad may rupture at any time |
| what is happening to blood vessel during an aneurysm? | blood accumulates between the tunics of the artery and separates them usually because of degeneration of the tunica media |
| what are the most common sites of aneurysm? | abdominal aorta, renal arteries, and arterial circle at base of brain |
| what happens during an aneurysm/symptoms? | -pain by putting pressure on other structures - can rupture causing hemorrhage |
| what causes aneurysms? | congenital weaknesses of blood vessels results of trauma bacterial infections such as syphilis MOST COMMON: ATHEROSCLEROISS AND HYPERTENSION |
| what are arterial sense organs? | sensory structures in the walls of certain vessels that monitor BP and chemistry; transmit info to brainstem that serves to regulate HR, vasomotion, and respiration |
| 3 arterial sense organs? | carotid sinuses, carotid bodies, and aortic bodies |
| carotid sinuses | baroreceptors (pressure sensors); in walls of internal carotid artery; monitors BP signaling brainstem; ex: High BP, set up vessel dilation to decrease HR; negative feedback loop to fix problem |
| carotid bodies | chemoreceptors; oval bodies near branch of common carotids; monitor blood chemistry; mainly transmit signals about respiratory to brain stem; adjust respiratory rate to stabilize pH, O2, CO2; CO2 LEVELS EFFECT IT MORE THAN O2 |
| aortic bodies | chemoreceptors; one to three in walls of aortic arch; same function as carotid bodies signal brainstem when respiratory things change; monitors pH, CO2, O2; CO2 LEVELS EFFECT IT MORE THAN O2 |
| what are capillaries? | site where nutrients, wastes, and hormones pass between blood and tissue fluid through the walls of the vessels (exchange vessels) |
| what are capillaries nickname | business end of the cardiovascular system |
| what do capillaries move? | gases and fluids |
| what are capillaries composed of? | composed of simple squamous endothelium and basal lamina in tunica interna |
| where are capillaries absent or scarce? | tendons, ligaments, epithelia, cornea, and lens of the eye |
| what are the three types of capillaries? | 1. continuous 2. fenestrated 3. sinusoids distinguished by ease with which substances pass through their wall and by structural difference that account for their greater or lesser permeability |
| continuous capillaries | most common; endothelial cells have tight junctions forming a continuous tube with intercellular clefts; allow passage of solutes such as glucose; pericytes |
| what is the main/default capillary? | continuous capillaries |
| pericytes | wrap around the capillaries and contain the same contractile protein as muscle; contract and regulate blood flow; around continuous capillaries |
| fenestrated capillaries | endothelial cells riddled with holes called filtration pores (fenestrations); spanned by very thing glycoprotein layer; allows passageway of small molecules; organs with absorption or filtration; ex: kidneys, small intestine |
| sinusoids | discontinuous capillaries; irregular blood filled spaces with large fenestrations; allow proteins (albumin), clotting factors, and new blood cells to enter the circulation; ex: liver, bone marrow (RBCs production), and spleen |
| continuous capillary's cell | 1 cell layer thick, has a BIG RBC; tight and small clefts; so tiny only 1 big RBC passes through |
| fenestrated capillary's cell | has clefts (between the cell) and fenestrations/holes in the cell |
| capillary beds | organized capillary networks; usually supplied by a single metarteriole |
| thoroughfare channel | metarteriole that continues through capillary bed to venule; bypasses the capillaries; direct route; |
| precapillary sphincter open | capillaries are well perfused with blood and engage in exchanges with the tissue fluid; SKELETAL MUSCLE IN MOTION |
| precapillary sphincter closed | blood bypasses the capillaries; flows through thoroughfare channel to venule; SKELETAL MUSCLE AT REST |
| ______of the body's capillaries are shut at a given time | 3/4s; when the capillaries are open and well pefrused |
| how much capacity of blood do veins have compared to the rest of the blood flow? | the most about 64%; big chunk of the pie |
| veins and blood flow | thinner walls (less muscular and elastic tissue); collapse when empty; easily expand; steady blood flow; merge to form larger veins |
| veins are subjected to relatively ______ blood pressure | LOW; remains 10mmHg with little function; because they have steady blood flow and further away from the ventricles |
| what are postcapillary veins | smallest veins; tunica interna with a few fibroblasts and no muscle fibers |
| what do postcapillary veins do? | more porous than capillaries so they exchange fluid with surrounding tissues; have most leukocytes emigrate through them |
| what are muscular venules? | up to 1 mm in diameter; one or 2 layers of smooth muscle in tunica media; have a thin tunica externa |
| what are medium veins? | up to 10mm in diameter; thin tunica media and thick tunic externa; tunica interna forms venous valves; |
| how are varicose veins formed? | blood pools in the lower legs in people who stand for long periods of time stretching their veins; form in part of the failure of the venous valves that help propel blood back to heart (cusps pull apart and backflow occurs); |
| what do the venous valves do? | skeletal muscle pump propels blood back toward the heart |
| what are venous sinuses? | veins with especially thin walls, large lumens, and no smooth muscle; not capable of vasomotion; examples: dural venous sinus and coronary sinus |
| what are large veins? | larger than 10mm; smooth muscle in all 3 layers; thin tunica media; tunica externa is thickest (longitudinal branches of smooth muscle); |
| what are some examples of large veins? | venae cavae, pulmonary veins, internal jugular veins, and renal veins |
| causes of varicose veins? | hereditary, weakness, obesity, and pregnancy; |
| Simplest and Most Common Circulatory Route | Heart-> Arteries -> Arterioles -> Capillaries -> Venules -> Veins; passes through ONLY ONE network of capillaries from the time it leaves the heart until the time it returns |
| Portal System Circulatory Route | blood flows through two consecutive capillary networks before returning to the heart; examples: between hypothalamus and anterior pituitary; in kidneys; between intestines and liver (hepatic portal system) |
| what is anastomosis? | the point where two blood vessels merge; to shunt blood to a different pathway in case of a block; in arteries its to keep blood flowing to a particular organ; also used to prevent blood flow to a particular area to save body (example: when freezing) |
| Arteriovenous Anastomosis Circulatory Route | artery flows directly into vein by passing capillaries; shunt blood flow |
| venous anastomosis | most common! one vein empties directly into another; reason vein blockage is less serious than arterial blockage |
| arterial anastomosis | two arteries merge; provide collateral alternative routes of blood to supply a tissue; coronary circulation and around joints (heart and brain main ones) |
| blood flow definition | the amount of blood flowing through an organ, tissue, or blood vessel in a given time mL/min |
| perfusion | the flow per given volume or mass of tissue in a given time mL/min/g |
| at rest total flow is ______ and is equal to ____ _____ | constant; cardiac output approx. 5.25L/min |
| hemodynamics | physical principles of blood flow based on pressure and resistance; Flow is proportional to the difference in pressure/resistance |
| increase pressure difference/gradient | increase blood flow |
| increase resistance | decrease blood flow |
| blood pressure | is the force that blood exerts against a vessel wall; measured at brachial artery of arm using sphygmomanometer; |
| systolic pressure | peak arterial BP taken during ventricular contraction (ventricular systole) |
| diastolic pressure | minimum arterial BP taken during ventricular relaxation (ventricular diastole) |
| normal value BP | 120/75mmHg |
| pulse pressure | difference between systolic and diastolic pressure; example:120/70 120-70=50 |
| mean arterial pressure MAP | the mean pressure one would obtain by taking measurements at several intervals throughout the cardiac cycle; diastolic pressure + 1/3 of pulse pressure; ex: 120/60 PP:60 1/3PP: 20 60+20=80MAP |
| why do we record the mean arterial pressure by only doing 1/3 of pulse pressure and all of diastolic pressure | diastole lasts longer than systole; Quiescent Period 0.4sec; Ventricular Contraction 0.3sec; Arterial Contraction: 0.1 sec |
| hypertension | high blood pressure; chronic is resting BP>140/90; consequences: can weaken small arteries and cause aneurysm |
| hypotension | chronic low resting BP; caused by blood loss, dehydration, anemia |
| Arteries stretch and recoil help prevent excessive blood pressure | expansion and recoil maintain steady flow of blood throughout cardiac cycle, smoothes out pressure fluctuations and decreases stress on small arteries |
| why does BP rise with age? | arteries lose that stretch and recoil ability absorb less systolic force |
| BP is determined by 3 things? | 1. cardiac output 2. blood volume 3. peripheral resistance |
| cardiac output | is HR X SV |
| increase water intake | increase BP |
| INCREASE RESISTANCE | increase BP |
| peripheral resistance 3 things | 1. blood viscosity 2. vessel length 3. vessel radius |
| peripheral resistance | the opposition to flow that blood encounters in vessels away from the heart |
| blood viscosity | thickness of blood; RBC COUNT AND ALBUMIN concentration elevate thickness of blood; increase BV with polycythemia and dehydration slow flow; decrease: anemia and hypoproteinemia (not enough albumin) |
| vessel length | the farther the liquid travels through a tube the more cumulative friction it encounters; pressure and flow decline with distance (ex: veins have little pressure after long flow) |
| vessel radius why is it important | MOST POWERFUL INFLUENCE OVER FLOW |
| vessel radius | only significant way of controlling peripheral resistance; vasomotion change in vessel radius; vasoconstriction or vasodilation changes quickly and easily |
| angiogenesis | new formation of blood vessels; happens because of tumor, clot, anastomosis, exercise, or fat |
| vessel radius also effects | blood velocity |
| lamina flow | blood velocity; flows in layers faster in center; blood flows FASTER in the MIDDLE; flow is proportional to the 4th power of the radius ex: 3^4 = 81; smaller changes in radius = big changes in flow |
| peripheral resistance: aorta to capillaries | blood velocity decreases for 3 reasons: 1. greater distance, more friction, reduce speed 2. smaller radii in arterioles and capillaries = more resistance 3. farther from the heart, more vessels, more area to cover |
| peripheral resistance: capillaries to vena cava | flow increases: 1. decreased resistance 2. large amount of blood forced into smaller channels 3. never regains velocity of large arteries; less pressure, greater flow farther away from heart |
| peripheral resistance: arterioles | most significant point of control over peripheral resistance and blood flow; 1. regulate flow into capillaries 2. most numerous (more than arteries) 3. more muscular in proportion to diameter |
| arteries have _____ smooth muscle layer but arterioles have more smooth muscle compared to their _____ | thicker; diameter (majority smooth muscle) |
| vasomotion | is a quick and powerful way of altering blood pressure and flow; |
| 3 ways to control vasomotion | 1. local control 2. neural control 3. hormonal control |
| 4 ways of local control | 1. autoregulation 2. vasoactive chemicals 3. reactive hyperemia 4. angiogenesis |
| autoregulation | local control; the ability of tissues to regulate their own blood supply; metabolic theory if tissue is inadequately perfused wastes accumulate stimulating vasodilation which increases perfusion |
| organ bad for autoregulation | skin |
| vasoactive chemicals | local control; substances secreted by platelets, endothelial cells, and perivascular tissue to stimulate vasomotion; vasodilators: histamine, bradykinin, prostaglandins, prostacyclin, and nitric oxide (Viagra); vasoconstrictors: endothelins |
| reactive hyperemia | local control; if blood supply is cut off then restored, blood flow increases above normal (blocking of water hose and then removing hand) |
| angiogenesis | local control; growth of new blood vessels; regrowth of uterine lining, coronary artery obstructions, exercised muscle, and malignant tumors; controlled by growth factors |
| neural controls | vessels under remote control by the central and autonomic nervous systems; control vasomotion |
| vasomotor center | of medulla oblongata exerts sympathetic control over blood vessels throughout the body; stimulates most vessels to constrict but dilates vessels in skeletal and cardiac muscle to meet demands of exercise |
| vasomotor center 3 autonomic reflexes | 1. baroreflexes 2. chemoreflexes 3. medullary ischemic reflex |
| baroreflexes | baroreceptors; neural control; an automatic negative feedback response to change in BP; carotid sinuses detect BP increase; signals sent to brainstem glossopharyngeal nerve; inhibit sympathetic, excite vagal fibers to slow down HR, CO, reducing BP; |
| baroreflexes is good for _____-_____ regulation of BP but not in cases of chronic hypertension | short-term |
| chemoreflexes | neural control; an automatic response to changes in blood chemistry; pH, CO2, O2; chemoreceptors called aortic bodies and carotid bodies; Primary Role: adjust respiration to changes in blood chemistry Secondary Role: vasomotion; const. raise lung flow |
| medullary ischemic reflex | neural control; automatic response to a drop in perfusion of the brain; medulla oblongata monitors blood supply; insufficient amount increase HR, vasoconstriction, Raise BP to RESTORE normal PERFUSION to BRAIN |
| emotion can also affect neural control | stress, anger, arousal all can raise BP |
| hormonal control | hormones influence blood pressure; some through their vasoactive effects (vasomotion) and other by regulating water balance |
| angiotensin II | potent vasoconstrictor; raises blood pressure, promotes Na and water retention by kidneys, increases BV and BP |
| atrial natriuretic peptide | increases urinary sodium excretion; reduces blood volume and promotes vasodilation; lowers blood pressure; reduced by atria when atria is too full |
| ADH antidiuretic hormone | promotes water retention and raise BP; pathologically high concentrations; also a vasoconstrictor |
| epinephrine and norepinephrine | most blood vessels: bind to alpha adrenergic receptors -vasoconstrictors; skeletal and cardiac muscle blood vessels: bind to beta adrenergic receptors - vasodilation |
| first purpose of vasomotion | general method of raising or lowering BP throughout the whole body; increasing BP requires medullary vasomotor center or widespread circulation of a hormone |
| second purpose of vasomotion | method of rerouting blood from one region to another for perfusion of individual organs; centrally: exercise sympathetic increase skeletal O2 and decreases kidney O2; locally: metabolite accumulation effects tissue not whole body |
| localized vasoconstriction | if a specific artery constricts the pressure downstream drops, pressure upstream rises; enables routing blood to different organs as needed ex: vigorous exercise dilates arteries in lungs heart and muscles, while vasoconstriction in kidneys and GI tract |
| more blood flows to _____ muscle when performing vigorous exercise | SKELETAL |
| capillary exchange | two way movement of fluid across capillary walls; water, O2, glucose, amino acids, lipids, minerals antibodies, hormones, wastes, co2, ammonia; |
| three routes chemicals pass through capillaries | 1. through endothelial cell cytoplasm 2. intercellular clefts btwn endothelial cells 3. filtration pores of the fenestrated capillaries mechanisms involved: diffusion, transcytosis, filtration, and reabsorption |
| diffusion | is the most important for capillary exchange; glucose & O2 being more concentrated in blood diffuse out of the blood to nearby tissue; CO2 & waste diffuse out of tissues into blood (excreted by kidneys/lungs) |
| capillary diffusion can only OCCUR IF | the solute can permeate the plasma membrane of the endothelial cell or find passages large enough to pass through (fenestrations) |
| lipid soluble substances | steroid, hormones, O2, CO2, diffuse easily through plasma membranes; pass through membrane |
| water soluble substances | glucose and electrolytes must pass through filtration pores and intercellular clefts; NEED WHOLES TO GO THROUGH |
| large proteins/particles | aren't permeable and can't pass through small holes for diffusion |
| transcytosis | endothelial cells pick up material on one side of the plasma membrane by pinocytosis or receptor mediated endocytosis, transport vesicles across cell, and discharge material on other side by exocytosis; important for albumin, fatty acids, and hormones |
| Blood hydrostatic pressure/ pushing | drives fluid out of capillary; high on arterial end of capillary, low on venous end; |
| Colloid osmotic pressure COP/pushing | draws fluids into capillaries; results from plasma proteins (ALBUMIN) more in blood; |
| hydrostatic pressure | pushing pressure; physical force exerted against a surface by a liquid; BP is an example |
| capillaries reabsorb about ____% of the fluid they filter | 85%; the other 15% is absorbed by the lymphatic system and returned to blood |
| Filtration and absorption occur where? | all throughout the capillary! |
| Net Filtration Pressure | more exits then comes in; number is higher towards the arterial end; stuff is still being absorbed |
| Net Reabsorption Pressure | more enters the blood then exits; number is higher towards venule end; stuff is still filtered |
| kidney capillaries | devoted to filtration; no reabsorption |
| alveolar capillaries | devoted to absorption; completely to keep fluid out of air spaces; no filtration |
| edema | the accumulation of excess fluid in a tissue; when fluid is filtered than absorbed; |
| 3 causes of edema | 1. increased capillary filtration: kidney failure, histamine release, old age, poor venous return 2. reduce capillary absorption: liver disease, dietary protein deficiency; 3. obstructed lymphatic drainage: surgical removal of lymph nodes |
| types of edema | tissue necrosis: o2 & waste delivery impaired pulmonary: suffocation; lungs cerebral: brain; headaches, nausea, coma, seizures severe edema/circulatory shock: blood; excess fluid in tissue spaces |
| venous return and 4 things that help it | the flow of blood back to the heart; 1. pressure gradient 2. gravity 3. skeletal muscle pump 4. thoracic respiratory pump |
| thoracic respiratory pump | inhalation - thoracic cavity expands and thoracic pressure decreases, abdominal pressure increases forcing blood upward; blood flows faster with inhalation; cardiac suction: sucks blood in front of aorta |
| exercise increase venous return | heart beats faster, increasing CO and BP, skeletal muscles, lungs, and heart dilate and increase flow, increased respiratory rate, increase thoracic pump, increased skeletal muscle pump |
| venous pooling | occurs with inactivity; venous pressure is not enough to force blood upward; prolonged standing = dizziness; |
| circulatory shock | any state in which cardiac output is insufficient to meet the body's metabolic needs cardiogenic shock: inadequate pumping of heart low venous return: CO is low b/c of little blood return to heart |
| 3 main forms of shock | 1. hypovolemic shock: common; loss of blood volume; trauma, burns, dehydration 2. obstructed venous return shock: tumor or aneurysm compressed a vein 3. venous pooling shock: long periods of standing, sitting, or widespread vasodilation |
| causes of shock | neurogenic shock: loss of vasomotor tone, vasodilation emotional shock to brainstem septic shock: bacterial toxins trigger vasodilation and increased capillary permeability anaphylactic shock: allergies; severe immune reaction to antigen, histamine |
| total blood flow to the brain fluctuates less than that of any other organ | seconds of deprivation causes loss of consciousness |
| main chemical stimulus: pH | CO2+ H20 -> H2CO2 -> H+ +(HCO3)- carbon dioxide + water -> carbonic acid -> hydrogen + bicarbonate ion |
| hypercapnia | CO2 levels increase the brain, pH decreases (acidic), triggers vasodilation |
| hypocapnia | raises pH (basic), stimulates vasoconstriction |
| transient ischemic attacks TIAs | brief episode of cerebral ischemia; mini-stroke; lack of O2 |
| stroke or cerebral vascular accident CVA | sudden death of brain tissue caused by ischemia |
| brachiocephalic | divides into right common carotid supplying right side of head; right subclavian supplying right shoulder and upper limb |
| left common carotid | supplying left side of head |
| left subclavian | supplying shoulder and upper limb |
| lungs are divided into | superior, middle, and inferior lobar arteries and left and right pulmonary arteries |
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