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blood vessels


blood vessels 64 % of blood volume is in the venous blood -acts as a reservoir system -blood in liver, spleen, & skin can be shaunted to other areas -emergency, raises skeletal muscle activity
inner layer endothelium/ tunica interna/ or inyama
arteries are ---------- than veins thicker
veins inner layer folds inward to form valves
arteries cannot contract instead they fold into pleats when artery contracts
endothelial cells act as sensors
the endothelium regulates vascular smooth muscle tone, host-defense reactions, angiogenesis, and tissue fluid hemostasis
middle layer tunica media
tunica media smooth muscle layer & elastic connective tissue -thicker in arteries than veins -innervated by sympathetic fibers of autonomic nervous system -vasoconstriction -vasodilation
vasoconstriction sympathetic stimulation(ANS) autoregulation- vessel wall damaged
vasodilation decreased sympathetic stimulation/ parasympathetic release of nitric acid presence of lactic acid
outer layer tunica externa/ or adventita
tunica externa mostly elastin and collagen fibers too thick for diffusion or osmosis vasa vasorum
vaso vasorum blood vessels in this layer of the large arteries & veins (28 layers of smooth muscle) provides blood flow to smooth muscle cells
artery lumen small
vein lumen large
arteries carry oxygenated blood from the left heart to the body except pulmonary artery -high pressure system -arterial system starts at aorta as it leaves LV
elastic/conducting arteries largest diameter arteries more connective tissue, less smooth muscle -helps propel blood forward while ventricles are relaxing
walls stretch to accommodate blood as ventricles contract after LV/RV contraction, elastin fibers in wall recoil walls also dampen the pressure peaks and valleys caused by heartbeat
recoil forces blood on toward smaller arteries
elastic/conducting arteries aorta brachiocephalic subclavians common carotid vertebrals pulmonary common iliac
brachiocephalic subclavian carotid
vertebrals off the subclavian
from the left ventricle to the aortic valve to the aorta recoil
muscular/ distribution arteries distribute blood to tissue of the body medium diameter arteries more smooth muscle, less connective tissue capable of greater vasoconstriction and vasodilation greater impact on blood flow
brachial and radial arteries femoral and tibial arteries external carotid arteries examples of muscular/ distribution arteries
aneurysm local arterial pressure exceeds the capacity of the elastic components of the tunics
arterioles several hundred million resistance vessels endothelium and only a couple layers of smooth muscle have greater influence on BP
resistance vessels when BP increases which increases resistance to blood flow
regulates blood flow into capillary system autoregulation arterioles
arterioles vasoconstriction decreases blood flow into capillaries
arterioles vasodilation increases blood flow to capillaries
ability of tissue to automatically regulate blood flow by adjusting vasoconstriction and vasodilation for metabolic demands autoregulation
precapillary sphincters rings of smooth muscle where capillaries branch from arterioles
capillaries microscopic connect arterioles and venules close contact with most of cells of the body diameter about the size of RBC
10 billion capillaries in body 25,000 miles exchange gases, nutrients, and waste occurs here
high need muscle, liver, brain, nerves, kidneys
lower need tendons, ligaments,fascia
no capillaries cornea , lens of eye, cartilage, all covering and lining epithelial tissue cells
single cell thick endothelial layer surrounded by basement membrane vary degrees of permeability depending on how tightly cells are joined ( cell junction)
continuous endothelium is a complete lining contain very tight junctions which limit permeability allows water, small solutes and lipid soluble substance through found everywhere except epithelia and cartilage many in muscles, lungs, CNS, thymus gland
fenestrated 10x more permeable than continuous capillaries "leaky" intracellular junction endothelium is fenestrated-contains "pores" rapid exchange of large amount of fluid and solutes can move through the pores found in endocrine glands, renal glomeruli, inte
discontinuous/ sinusoid -specialized fenestrated capillaries -wide gaps between endothelial capillaries -allows large molecules like proteins and RBCs to pass through -found in liver, spleen, bone marrow, anterior pituitary gland, adrenal glands
capillary bed group of interconnected capillaries
collaterals multiple arteries that feed a single capillary bed if 1 artery is blocked, the capillary bed will still receive blood flow
AV malformation the capillary bed is missing high pressure arterial blood flows directly into the low pressure venous system extremely fragile, prone to bleeding, can be very painful exchange of nutrients & waste in this area a bruit may also be heard on auscultation
capillary pore red arrow= pore, L= lumen, blue arrow, P= perivascular space
capillary exchange small diameter-blood flow is slower than in larger vessels slow speed allows for capillary exchange substances move via diffusion, osmosis, and filtration
substances that move via diffusion, filtration, and osmosis o2, co2, and anesthetic gases diffuse though quickly
filtration involves capillary blood pressure/ hydrostatic pressure blood colloid osmotic pressure
capillary blood pressure/ hydrostatic pressure pressure of blood against the walls of the capillary generated by LV contraction, pressure "pushes" fluid out through pores and into insterstitial fluid- filtration pressure is higher at arteriolar end than venule end
blood colloid osmotic pressure an opposing pressure that "pulls" fluid back into the capillary "pressure" is due mainly to plasma proteins proteins molecules are too large to pass through the pores, they stay in the capillaries osmotic pressure created by proteins in the plasma :pul
osmosis movement of a solvent/ water from an area of lower solute concentration to an area of greater concentration 1
osmotic/water potential if pure water is on both sides of a semipermeable membrane, there will be no movement-no osmotic potential
when you add solutes to the water , an osmotic potential is created decreased osmotic potential= water is less likely to move to another area increased osmotic potential= water is more likely to move to another area
edema abnormal accumulation of fluid in the insertital fluid space increased capillary blood pressure/ hydostatic pressure decreased plasma protein/albumin increased permeability of capillaries and proteins leak out-water follows
inflammatory mediators histamins, bradykinin
lymph system drains excess interstitial fluid transport dietary lipids carries out immune responses
LYMPH interstitial fluid that has moved into a lymph vessel: similar to plasma
lymph vessels starts as lymph cappilRIES; become larger empty into 2 main vessels- right lympathic duct and thoracic duct
right lymphatic duct and thoratic duct drain into subclavian veins
lymph nodes masses of lymph tissue; act as a filter contain macrophages and lymphocytes
spleen contains macrophage and B a lymphocytes
thymus gland located in mediastinum; makes thymosin (stimulates t lymphocyte maturation) contains large numbers of lymphocytes
lymphatic nodules tonsils, Peyers patches (small intestines), also found in mucous membrane lining respiratory, urinary, GI and reproductive tracts
start as blind-ended vessels & found throughout the body wherever capillaries are found except parts of the spleen, red bone marrow, and tissue with no capillaries(cornea, lens of eye) lymph capillaries
endothelial cells of lymph capillaries not attached end to end they overlap one another when pressure outside the vessel exceeds the pressure inside. cells separate slightly-like swing doors and moves into the capillary
venules and vein carry deoxygenated blood from body towards heart capitance vessels- 64% of total blood volume is in venous system low pressure system endothelium form valves to prevent back flow
venules formed by union of several capillaries
veins formed by union of several venules
varicose veins insufficient/weak valves
venous return volume of blood flowing back to heart
ventricular systole skeletal pump respirartory pump 3 ways how venous return
skeletal pump compression of veins during skeletal muscle contraction milking blood moves from 1 valve to another
ventricular systole blood pressure helps push blood through venous system
respiratory pump inhalation and exhalation
inhalation intrathoracic pressure decreases as the diaphragm moves down & intraabdominal pressure increases abdominal veins are compressed, blood is squeezed toward the heart
exhalation diaphragm moves up which increases intrathoracic pressure intraabdominal pressure decreases valves prevent backflow of blood into abdominal veins
autoregulation/endothelium changes pressure locally
neural mechanisms autonomic nervous system (sympathetic and parasympathetic)
endocrine mechanisms hormones
local vasodilators chemical released at tissue level relax smooth muscles of precapillary sphincters speed up blood flow into those tissues
examples increases co2 or decreases o2 at the local tissue level lactid (not enough oxygen) nitric oxide (no) released by endothelial cells elevated K+ or H+ concentration in interstitial fluid chemical associated with inflammation(histamine) elevated local
lack of autoregulation lose ability to release NO raynaulds's disease, Prinzmetal angina (vasopastic angina)
factors affecting tissue perfusion cardiac output peripheral resistance blood pressure
active cells require more oxygen and nutrients and produce more waste= increased circulation
prostaglandins activated plateletsand wbc's
thromboxane a2 activated platelets and wbc's
endothelins endothelial cells
local vasoconstrictors chemicals released by damaged tissue cells & platelets during formation contract smooth muscles of precapillary sphincters decrease blood flow through local tissue
cardiovascular center located in the medulla oblongata regulates HR, force of contraction, SV, and BP comprised of cardiac center (HR) and vasomotor center (BP) receives info from areas of the brain and sensory receptors
cardiac centers contains cardioacceleratory nerves (increases CO via sympathetic stimulation) cardioinhibitory nerves (decreases Co via parasympathetic stimulation)
vasomotor center contains many neurons responsible for vasoconstriction (adrenergics, neurons, release norepinephrine)
small # of neurons that cause vasodilation of arterioles in brain and skeletal muscles cholinergic neurons, release acetylcholine (ach) ach stimulates the release of NO by endothelial cells in area NO causes vasodilation some neurons release NO as their neurotransmitter
vasomotor tone sympathetic nervous stimulation keeps arterioles in a state of partial vasoconstriction they can dialate 11/2 x their diameter resistance in a maximally constricted arteriole is 80x greater than fully dialted arteriole
sensory receptors proprioceptors baroreceptors chemoreceptors
proprioceptors message of joint and muscle movement during physical activity increases HR
baroreceptors reflexes sensory dendrites that trigger a vascular reflex send continuous messages about BP and CV center(medulla) to adjust CO and peripheral resistance monitor degree of stretch in arteries
carotid sinuses bases of internal carotid arteries responds 60-180 mmHg
aortic sinuses wall of ascending aorta wall of right atrium
baroreceptors when BP increases they are stimulated send impulse to CV center at a faster rate CV center increases parasympathetic stimulation & decreases sympathetic stimulation ach released at SA node & force of contraction decreased HR vasomotor centers inhibit
when BP fall below normal decrease stretch- baroreceptors send nerve impulses to slow rate-CV center , parasympathetic stimulation decreases & sympathetic stimulation, BP, CO and vascular resistance , HR and force of contraction increases (vasomotor center stimulated vasoconstri
atrial baroreceptors dendrites in wall of RA, blood should pump into the aorta at the same rate as it is returning to the RA. If BP rises in RA -blood is returning faster than it is leaving. sends impulses to CV centers to increase CO until balance returns
valsalva maneuver happens when u forcefully exhale while keeping ur mouth and nostrils closed increases intrathoracic pressure aortic & carotid baroreceptors are stimulated triggering reflexive action reflexes causes increased HR & vasoconstriction increases BP glottis
regulation chemoreceptor reflexes monitor blood & cerebrospinal fluid levels located in 2 carotid bodies of common carotid arteries
hypoxia, acidosis, & hypercapnia stimulates chemoreceptors
sympathetic stimulation of arterioles & venules = vasoconstriction = increased BP and CO
renin-angiotensin aldosterone (RAA) system decrease BP, BF through kidney, is secreted by juxtaglomerular cells in kidney renin converts angiotensiogen (liver) n 2 angiotensin I
angiotensin I is converted into angiotensin II by ACE in the lungs
angiotensin II is most potent & causes increased BP, CO, positive inotropic effect on the heart. secretion of aldosterone and ADH, stimulates hypothalamus to initiate thirst
aldosterone increases reabsorption of sodium & water in kidney
adh increases reabsorption of water
epinephrine and norepinephrine released by adrenal medulla in sympathetic stimulation increase HR & force of contraction which increases CO causes vasoconstriction of arterioles & veins in skin and abdominalpelvic organs increases BP
erythropoietin stimulates vasoconstriction, increases rbc production, increases the volume & viscosity of blood
antidiuretic (adh) produced by hypothelmus, secreted by posterior pituitary released in dehydration & decreased blood volume stimulates vasoconstriction stimulated reabsorption of water n kidney increase BP increase Blood volume
atrial natriuretic peptide (ANP) released by cell in RA of heart in response to excessive stretching stimulates excretion of sodium & water in urine stimulates vasodilation, blocks release of ADH, aldosterone, epinephrine, & norepi reduces BP & blood volume
blood pressure pressure exerted by blood o the walls of the blood vessel, created by LV contraction=systole starts around 100 mmHg at aorta to 35 mmHg in capillaries
capillary hydrostatic pressure 35-18 mmHg
venous pressure 18-1 mmHg
circulatory pressure 100mmHg
total peripheral resistance (TPR) resistance of the entire cardiovascular system
pressure gradient in arterial system 100mmHg(aorta) to 35 mmHg (caps) =65 mmHg
circulation= circulatory pressure> TPR
vascular resistance blood viscosity turbulence creates TPR/SVR
Vascular resistance force that opposes blood flow in blood vessels created by friction between blood & blood vessel walls most significant component determined by vessel length and vessel diameter
blood viscosity thin fluids flow well at low pressures, resistance to flow created by interactions among molecule &suspended materials in a liquid thicker fluids need higher pressure to push them whole blood is 5x thicker than water due to plasma proteins & blood cells
changes in anemia and polycythemia blood viscosity
viscosity increases in dehydration n polycythemia & decreases in anemia, overhydration
turbulence normally occurs as blood flow between atria and ventricles, in large arteries when CO & arterial flow rates are high, bifurcation areas. creates swirls of blood in the blood vessel seldom occurs in small vessels unless walls are damaged
maintains blood flow through capillary beds arterial blood pressure
pulse pressure difference between systolic and diastolic pressure
mean arterial pressure single number to represent blood pressure average is 70-110 mmHg 60mmHg =ischemia MAP
blood pressures aorta/large arteries 100-120 mmHg arterioles 60-70 mmHg capillaries 25mmHG (aterial side) 11mmHg (venous side) venules 15mmHg veins 5-6 mmHg venae cava 0 mmHg
the difference between systolic and diastolic pressure recoil
aortic compliance helps the aorta absorb some of the force of the blood surge as it expands during systole decreases pulse pressure as aorta gets less compliant -pulse pressure increases
Created by: t4achange
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