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A&P2 Exam 2

Chapter 18

arteries carry blood away from heart, they branch into vessels of progressively smaller diameter that supply most tissues in body with blood
pulmonary circuit transports blood between heart and lungs
systemic circuit transports blood between heart and rest of body
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
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
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
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
tunica externa composed of dense irregular collagenous connective tissue that supports blood vessel and prevents it from overstretching
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
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)
elastic (conducting) arteries largest diameter; include aorta, brachiocephalic, subclavian, carotid; nearest to heart and therefore highest pressure of any vessels
baroreceptors pressure receptors
chemoreceptors detect blood oxygen, carbon dioxide, and hydrogen ion concentrations
muscular arteries (distributing arteries) intermediate in diameter; well-developed tunica media composed of smooth muscle cells; include most named arteries that supply organs
arterioles smallest arteries; contain all 3 layers but layers are extremely thin, and tunica media contains only1-3 layers of smooth muscle
metarterioles smallest arterioles; directly feed capillary beds in most tissues; contain precapillary sphincters that encircle metarteriole-capillary junctions
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
What percent of total blood in the body is located in the veins? This allows veins to function as__________. 70%, blood resevoirs
Smallest veins? They drain blood from capillary beds through __________. venules; postcapillary pvenules
postcapillary venules extensions of tunica intima that prevent blood from flowing backward; numerous in veins of legs, where blood flow opposed to gravity
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
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
vascular anastomoses connect via pathways called collateral vessels
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
venous anastomosis most common type; neighboring veins are connected by small collaterals; smaller veins are often so interconnected that they form complex, weblike patterns
arteriovenous anastomosis artery empties directly into a vein without passing through a capillary bed
hemodynamics physiology of blood flow in the cardiovascular system, basic concepts related to blood flow
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
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
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
radius of vessel varies inversely with resistance; as radius increases resistance decreases
blood viscosity inherent resistance that all liquids have to flow
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
obstruction blood clot, fatty plaque
laminar perfect flow, moves in layers, blood is central (faster in middle, slower near walls)
turbulent when there is an obstruction, blood flow spins/ moves around obstruction; can cause blood clots
vascular compliance onset by ability of vessels to stretch
15; 95 Blood pressure averages __mm Hg in the pulmonary circuit and __,, Hg in the systemic circuit.
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
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
Mean arteriolar pressure (MAP) average pressure in systemic arteries during an entire cardiac cycle; generally measures about 95 mm Hg
systolic pressure (SP) pressure generated by ventricular contraction; averages about 120mm Hg at rest in in aorta, 110 in brachial arteries
Diastole pressure (DP) pressure generated by ventricular relaxation; average 80mm Hg at rest in aorta, 70 in brachial arteries
Pulse Pressure (PP) difference between systolic and diastolic pressure
Instruments used to measure arterial blood pressure Sphygmomanometer on arm, stethoscope
formulas for MAP and PP MAP=diastolic+1/3 (systolic-diastolic) PP=systolic- diastolic
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
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
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
nervous system maintenance of blood pressure control of homeostasis is the autonomic nervous system via 2 divisions: sympathetic and parasympathetic
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)
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
the baroreceptor reflex negative feedback loop that responds to increases or decreases in BP
baroreceptor reflex: stimulus blood pressure increases above normal range
baroreceptor reflex: receptor baroreceptors in the carotid sinus detect the increased pressure and fire action potentials in a faster rate
baroreceptor reflex: control center the impulses travel to the medulla of the brainstem for integration
barorececptor reflex: effector/ response parasympathetic neurons in the medulla oblongata inhibit sympathetic activity, blocking vasodilation and decreased HR, lowering CO
baroreceptor reflex: homeostatic range blood pressure decreases, and feedback decreases response from the medulla
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
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)
Central Chemoreceptor Stimulation Respond to decreases in pH in brain; increases activity of sympathetic neurons; result in vasoconstriction and increase in blood pressure
Hormones that control cardiac output epinephrine, norepinephrine, thyroid hormone
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
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.
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.
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
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
pre-hypertension systolic 120-139 mm Hg, diastolic 80-99 mm Hg
hypotension low blood pressure; systolic pressure lower than 90 mm Hg and/or a diastolic pressure lower than 60 mm Hg
tissue prefusion blood flow to a tissue through a capillary bed
capillary structure simple squamous epithelium, endothelium, tunica intima; basal lamina secreted by endothelial cells
pericytes cells found around some capillaries; have contractile filaments and appear to control blood through capillaries
capillary exchange movement of nutrients, gases, ions, and wastes across the wall and travel between the blood in the capillary and the tissue cells
intercellular gaps and fenestrations diffusion and osmosis of water and water-soluble materials such as monosaccharides and amino acids
simple diffusion lipid-soluble materials diffuse through membranes of epithelial cells; steroids, gases, fatty acids
transcytosis large water-soluble compounds brought into cell by endocytosis and released by exocytosis to interstitial fluid
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)
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)
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)
microcirculation involves true capillaries, where materials are exchanged, and a small, central vessel
metarteriole- capillary beds central vessel of proximal end
precapillary sphincters-capillary beds controls amount of blood flowing into capillaries
thouroughfare channel- capillary beds central vessel of distal end, movement of blood in one direction
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
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
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
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
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
skeletal muscle- tissue prefusion blood flow increases during exercise; metabolic control due to increasing metabolic needs
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
filtration the movement of a fluid by a force such as pressure or gravity (moves water across capillaries)
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
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
colloid osmotic pressure (COP) oncotic pressure; difference in osmotic pressure that creates as osmotic pressure gradient
equation to find capillary net filtration pressure (NFP) NFP = (HPcap – HPif) - (OPcap – OPif)
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
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.
edema condition characterized by an excessive amount of water in the interstitial fluid
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
ascites accumulation of fluid in abdomen
peripheral edema edema found in hands and feet where hydrostatic pressure gradient is already slightly higher due to effects of gravity
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
risk factors of stroke hypertension, atherosclerosis (particularly in carotid arteries), diabetes mellitus, cigarette smoking, hypercholesterolemia, and a cardiac dysrhythmia called arterial fibrillation
Created by: 903508329791262