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Ch 20-Cardio: BV

The Cardiovascular System: Blood Vessels

QuestionAnswer
blood vessels form a closed delivery system that begins & ends @ the heart
3 major types of blood vessels are arteries, capillaries & veins
arterioles smallest branches in the arteries that feed into the capillary beds of body organs & tissues. regulate blood flow into capillary beds by vasoconstriction or vasodilation.
venules where blood draining from the capillaries flows
artieries & veins act as ____ for blood conduits
arteries carry blood ______ the heart away from
arteries carry blood that is _________in oxygen high
veins cary blood _______ the heart toward
veins carry blood that is _________in oxygen low
exchanges between blood & tissue cells occur through gossamer-thin capillary walls
wall of all blood vessels are composed of 3 distinct layers (tunics)
vessel lumen a central blood-containing space that is surrounded by tunics
innermost tunic is the tunica interna/ tunica intima; in intimate contact with the blood in the lumen; contains the endothelium
endothelium simple squamous epithelium lines the lumen of all vessels, continuation of the endocardial lining of the heart, forms a slick surface that minimizes friction as blood moves through the vessel lumen
subendothelial layer present in vessels larger than 1mm in diameter; loose connective tissue (basement membrane) supports the endothelium
tunica media middle tunic, circularly arranged smoth muscle cells & sheets of elastin; critical in regulating circulatory dynamics (bulkiest layer in arteries, cheif resp. for maintaining bp & continuous blood circ)
vasomotor nerve fibers regulates the activity of the smooth muscle; present in the sympathetic division of the autonomic nervous sytem & a whole battery of chemicals
vasoconstriction reduction in lumen diameter due to smooth muscle contraction
vasodilation widening of the lumen due to smooth muscle relaxation
tunica externa tunica adventitia (outermost layer of blood vessel wall) composed of loosely woven collagen fibers, filled w/ nerve fibers & lymphatic vesels; in lg veins (its a network of elastin fibers)
why do tunica externa have collagen fibers? portects & reinforces the blood vessel & it anchors it to surrounding structures
vasa vasorum "vessels of the vessels" (present in larger vessels; its a system of tiny blood vessels); nurishes the more external tissues of the blood vessel wall
arteries vessels that transport blood away from the heart
systemic arteries carry oxygenated blood
systemic veins carry oxygen-poor blood
3 groups of arteries elastic, muscular & arterioles
elastic artieries (conducting arteries) thick-walled arteires near the heart--the aorta & it's maajor branches, have a large lumen contain substantial amounts of smooth muscle
why are elastic arteries known as conducting arteries? b.c their large lumen allows them to serve as low-resistance pathways that conduct blood for the heart to medim0sized arteries
where are elastic arteries seen most in? tunica media
how is their reaction in vasoconstriction they are relativly inactive, even though the contain substantial amounts of smooth muscle
arteriosclerosis (narrowing of arteries) when blood vessels become hard & unyielding, causes blod to flow more intermittently
muscular arteries (distributing arteries); deliver blood to specific body organs & account for most of the named arteries studied (have thickest media of all vessels); more active in vasoconstriction & less distensible
what is present on the face of the tunica media in muscular arteries elastic lamina
arterioles smallest of the arteries; have chiefly smooth muscle with few scattered elastic fibers
the smaller arterioles lead into the capillary beds
fibrous or atherosclerotic plaques production of fibrous lesions w/ a core of dead & dying foam cells
capillaries smallest blood vessels
what are in their walls? thin tunica interna
pericytes smooth muscle-like cells that stabilize the capillary wall
what are poorly vascularized by capillaries? tendons & ligaments
what lack capillaries andy how do they receive nutrients cartilage & epithelia lack apillaries, receive nutrients from blood vessels in nearby connective tissues & the avascular cornea & lens of the eye receive nutrients from the aqueous humor
capillaries role is to exchange materials (gases, nutrients, hormones between blood & interstitial fluid
name they types of capillaries continuous, fenestrated, & sinusoidal
continuous capillaries abundant in skin & muscles;
intercellular clefts incomplete, gaps of unjoined membrane caused by adjacent cells of continuous capillaries; thay are large enough to allow limited passage of fluids & small solutes
fenestrated capillaries similar to continuous except their endothelial cells are riddled with oval pores, or fenestrations (fenestra=window)
what covers fenestrations delicate membrane, or diaphram
where are fenestrated capillaries found where active capillary absorption or filtrate formation occurs (ex. in sm. intes. receive digested food nutrients & those in eno organs allow hormones rapid entry into the blood (FC- w/ perpetually open ores occur in the kidneys where rapid filtration of
sinusoids sinusoidal capillaries;leaky capillaries found only in certain organs (liver, bone marrow, lymphoid tissues & some endocrine organs); large irreularly shaped lumens are usually fenestrated
in the liver endothelium of the sinusoids is ____ discontinuous
Kupffer cells large macrophages that form part of the lining in the endothelium part of the liver of the sinusoids
capillary bed interweaving network formed by capillaries
microcirculation flow of blood from an arteriole to a venule (capillary bed)
a capillary bed consists of 2 types of vessels (1) vascular shunt (metarteriole-thoroughfare channel) (2) true capillaries, he actual excchange vessels
what is a vascular shunt? a short vessel that directly connects the arteriole & venule @ opposite ends of the bed
the ___ feeding the bed leads into a _____ which is directly continuous w/ the _____ terminal arteriole; metarterile; thoroughfare channel
what is a metarteriole a vessel structurally intermediate between an arteriole & a capillary
what is a thoroughfare channel intermediate between a capillary & a venule
the thoroughfare channel, in turn, joins the ___ that drains the bed postcapillary venule
true capillaries branch off the metarteriole (proximal end of the shunt) & return to the thoroughfare channel (distal end), but can sometimes spring from terminal arteriole & empty directly into the venule
precapillary sphincter cuff of smooth muscle fibers; surrounds the root of each true capillary @ the metarteriole & acts as a valve to regulate the flow of blood into the capillary
blood flowing through a terminal arteriole may take what routes either through the true capillaries or through the shunt
venules formed when capillaries unite
postcapillary venules smallest venules, consist entirely of endothelium around which a few pericytes congregate
veins form when venules join
capacitance (blood reservoirs) refers to veins b.c. up to 65% of the body's total blood supply is found there
venous valves formed from folds of the tunica interna, the resemble the semilunar valves of the heart in both structure & function
varicose veins veins that have become tortuous & dilated b.c of incompetent vlaves
hemorrhoids resulting variocosites in the anal veins
venous sinuses (coronary sinus of the heart & dural sinuses of the brain are highly specialized, flattened veins w extremely thin walls composed only of endothelim)
vascular anastomes where vascular channels unite
arterial anastomses when arteries supplying the same territory often merge bc most organs receive blodd from more than one arterial branch
collateral channels the alternate pathways provided by arterial anastomoses
arteriovenous anastomoses the metarteriloe--thoroughfare channel shunts of capillary beds that connect arterioles & venules
blood flow actual volum of blood flowing through a vessel, an organ, or the entire circulation in a given period (ml/min)
BP force per unit area exerted on teh wall of a blood vessel by its contained blood
resistance opposition to flow & is a measure of the amount of friction blood encounters as it passes through the vessels (peripheral resistance(PR))
blood viscosity internal resistance to flow & is related to the thickness or "stickiness" of a fluid
Total blood vessel length relationship between total blood cessel length & resistance; longer total vessel length, greater resistance encountered
blood vessel diameter fluid close to the walls of a tube or channel is slowed by friction as it passes along the wll, whereas fluid in the center of the channel flows more freely & faster
systolic pressure when the L ventricle contracts & expels blood into the aorta, it imparts kinetic energy to the blood, which in turn stretches the elastic aorta as aortic pressure reaches its peak (*pressure peak)
diastolic pressure aortic pressure drops to its lowest level (approx. 70 80 mm Hg)
pulse pressure differenece between systolic & diastolic pressures (throbbing pulsation in an artery during systole)
MAP mean arterial pressure; propels the blood to the tissues throughout the cardiac cycle
respiratory pump sucks blood upward toward the heart, as we inhale, abdominal pressure increases; caused by pressure changes occurring in ventral body cavity during breathing
muscular pump skeletal muscle activity; it milks bolood toward the heart, & once blood passes each successive valve, it cannot flow back; this is bc the skeletal muscles surounding the deep veins contract & relax
vasomotor center neural center that oversees changes in the diameter of blood vessels; a cluster of sympathetic neurons in the medulla
cardiovascular center integrates bp control by altering cardiac output & blood vessel diameter
vasomotor fibers sympathetic efferents (motor fibers) where the vasomotor center transmits impulses at a fairly steady rate along; the exit fm the T1 through L2 levels of the spinal cord & run to innervated the smooth muscle of blood vessels, most import arterioles
vasomotor tone a state of moderate constriction
carotid sinus reflex protects the blood supply to the brain
aortic reflex concerned with maintaining adequate bp in the systemic circuit as a whole
changing levels of oxygen & carbon dioxide help regulate bp via the ____ chemoreceptor reflexes
adrenal medulla hormones are norepinephrine (NE) & epinephrine; released during periods of stress
what does NE & E do? enhances the sypathetic fight-or-flight response (increase BP)
more specifically what does NE do? has a vasoconstrictive action
what does epinephrine do increases cardiac output & promotes generalized vasoconstriction (except in skeletal & cardiac muscle, where it generally causes vasodilation)
what effects does nicotine have mimics the effects of catecholamines, causes intense vasoconstriction not only by direct stimulating ganglionic sympathetic neurons but also by prompting release of lg amounts of E & NE
ANP atrial natriuretic peptide; a peptide hormone produced by the atria of the heart that causes blood volume & BP to decline; antagonizes aldosterone & prods the kidneys to excrete more sodium & h2o fm the body, causing blood volume to drop; also causes gen
ADH (antidiuretic hormone) produced by hypothalamus & stimulates the kidneys to conserve water, when BP falls to dangerously low levels (sever hemorhage) muchmore ADH is released & helps to restore arterial pressure by causing intense vasoconstriction
angiotensin II generated in response to renin released by the kidneys when renal perfusion is inadequate; causes intense vascoconstriction, promoting rapid rise in systemic bp; also stimulates rlease of aldosterone & ADH which act in long-term regulation of bp by enhanc
endothelium source of several chemicals that affect vascular smooth muscle (as well as blood clotting) ex. peptide endothelin is one of most potent vasocon., released in response to low blood flow, it appears to bring about long-lasting effects by enhancing calcium e
PDGF also relased by endothelia cells (prostaglandin-derived growth factor), another vasocons chem.
NO nitric oxide; called endotheliumdervied relaxing factor; is released in direct response to a high blood flow & signaling molecules such as acetylcholine & bradykinin (& the vasodilator nitroglycerine) & its released is a 2ndary or consequent response to t
NO acts via a cyclic GMP 2nd messenger system, promotes both reflex (systemic) & highly localized vasodilaion
NO is quickly destroyed
histamne, prostacyclin, kinins, & certain chemicals are released during inflammatory response & certain allergic responses are potent vasodilatores; promote fluid loss fm bloodstream by increasing cappillary permeability
alcohol causes bp to drop by inhibiting ADH release, by depressing the vasomotor center, & by promoting vasodilation, esp. in skin (accounts for flushed app. of someone who has drunk a gen am of alc
renin-angiotensin mechanism involves indirect renal mech.
when arterial bp declines, special cells inthe kidneys release the enzyme____ renin into the blood
renin triggers a series of enzymatic reactions that produce ____ angiotensin II (potent vasoconstrictor, promoting an increase in bp, increases rate of blood delivery to the kidneys & renal perfusion
aldosterone hormone that enhances renal reabsorption of sodum, & prods the post pit release DH (promotes more water reabsorption (stimulated by the adrenal cortex)
pressure points points that are compressed to stop blood flow into distal tissues during hemorrhage (ex seriously lacerate your hand, you can slow or stop the bleeding by compressing the radial or brachial artery)
hypotension low blood pressure (systolic bp below 100 mm Hg
orhostatic hypotension temporary low bp & dizziness when they rise sudenly fm reclining or sitting position
chronic hypotension hints poor nutrition, bc poorly nourished are often anemic & have inadequate levels of blood proteins
hyper tension high bp (common in obese people bc the total length of their blod vessels is relatively greater than that in thinner individuals
about 90% of hypertensie people have___ or ___ ___ in which no underlying cause has been identified primary, or essential, hypertension
secondary hypertension accounts for 10% of cases, due to indentifiable disorders such as excessive renin secretion by the kidneys, arteriosclerosis, & endocrine disorders such as hyperthyroidism & Cusching's disease
tissue perfusion blood flow through body tissues involved (1) delivery ofoxygen & nutrients to & removal of wastes f tissue cells (2) exchange in the lungs (3) absorption of nutrients fm diges trach & (4) urine formation by the kidneys
autoregulation automatic adjustment of blood flow to each tissue in proportion to its requirements at any point in time
myogenic responses (blank)
reactive hyperemia dramatic increae in blood flow into a tissue thatoccurs after the blood supply to an area has been temp blocked
active/exercised hyperemia phenomenon whenmuscles become active, blood flow increases (hyperemia) in direct proportion to their greater metabolic activity
vasomotion reflects the on/off opening & closing of precapillary sphincters in response to local autoregulatory controls
diffusion when O, CO & nutrients & metabolic wastes pass between the blood & interstitial fluid via ___
capillary hydrostatic pressure (HPc) tends to force fluids through the capillary walls
interstitial fluid hydrostatic pressure (HPif) opposes the bp which forces fluid out of the capillaries acting outside the capillaries (back pressure) pushing fluid in
capillary colloid osmotic pressure (OPc) (oncotic pressure); developed by the abundant plasma proteins in capillary blood (primarily albuminmolecues) approx 26 m Hg
net filtrationpressure (NFP) determine whether there is a net gain or net loss of fluid fm the blood; considers all of the forces acting at the capillary bed
circulatory shock any condition in which blood vessels are inadequately filled & blood coannot circulate normally
hypovolemic shock results from large-scale loss of blood, as might follow acute hemorrhage, sever vomiting or diarrhea or extensive burns
cardiogenic shock pump failure, occurs when the heart is so inefficient that it canot sustain adequate circulation
vascular system used when referring to the body's complex network of bloos vessels
blood islands the endothelial lining of blood vessels is formed by mesodermal cells, which collect in little masses
Blood is carried in a closed system of vessels that begins and ends at the heart
The three major types of vessels are arteries, capillaries, and veins
Arteries carry blood away from the heart
veins carry blood toward the heart
Capillaries contact tissue cells
Capillaries directly serve cellular needs
The three tunics that arteries and veins are composed of tunica interna (intima), tunica media, and tunica externa
central blood-containing space surrounded by tunics Lumen
the tunica intima reduces friction between the blood and the blood vessels
the tunica media controls vasoconstriction and vasodilation
the tunica externa ________, _______ & ______the blood vessel to surrounding structures protects, reinforces and anchors
Elastic or conducting arteries contain what? & what does this allow? large amounts of elastin, which allows these vessels to withstand and smooth out the pressure fluctuation due to the pumping action of the heart.
Muscular or distributing arteries deliver blood to specific body organs
What type of arteries have the most tunica media of all the vessels? Muscular or distributing arteries.
These vessels are active in vasoconstriction Muscular or distributing arteries
Arterioles the smallest arteries
Arterioles regulate blood flow into capillary beds vasoconstriction or vasodilation.
Capillaries the smallest blood vessels
Capillaries allow for exchange of substances between the blood and interstitial fluid
There are three structural types of capillaries continuous, fenestrated, and sinusoids
Continuous capillaries allow passage of fluids and small solutes
Most common type of capillaries Continuous capilaries
Fenestrated capillaries are more permeable to fluid and solutes than continuous capillaries
Fenestrated capillaries are found wherever active capillary absorption or filtrate formation occurs (e.g., small intestines, endocrine glands, and kidneys)
Sinusoidal capillaries are leaky capillaries with large lumens;
Sinusoidal capillaries allow large molecules (proteins and blood cells) to pass between the blood and surrounding tissues
Where are Sinusoidal capillaries found? in the liver, bone marrow, lymphoid tissue, and in some endocrine organs
How does Blood flow within Sinusoidal capillaries? sluggishly, allowing for modification in various ways
Capillary Beds are Microcirculatory networks
Capillary Beds consist of 1.Vascular shunts 2.True capillaries
True capillaries function as the exchange vessels
Vascular shunts metarteriole-thoroughfare channel connecting an arteriole directly with a postcapillary venule
precapillary sphincter A cuff of smooth muscle that surround each capillary at the matearteriole and acts as to regulate blood flow into the capillary
Venules and Veins are found in what system? Venous System
Where are Venules formed? where capillaries converge
Venules allow fluid and white blood cells to move easily between the blood and tissues
When venules converge what are formed? Veins are formed
Veins are formed when venules converge
Veins are relatively thin walled with large lumens
Veins contain about ¬¬¬¬¬____% of the blood supply 65%
Veins have much _________blood pressure and _______walls than arteries lower, thinner
To return blood to the heart, veins have special adaptations What are they and describe each 1.Large-diameter lumens, which offer little resistance to flow 2.Valves (resembling semilunar heart valves), which prevent backflow of blood
Vascular Anastomoses Merging blood vessels, more common in veins than arteries
Arterial anastomoses provide alternate pathways (collateral channels) for blood to reach a given body region
If one branch is blocked (regarding Arterial anastomoses) the collateral channel can supply the area with adequate blood supply
Blood Flow Actual volume of blood flowing through a vessel, an organ, or the entire circulation in a given period:
Blood Flow is measured in ml per min.
Blood Flow is relatively constant when at rest
Blood Pressure (BP) Force per unit area exerted on the wall of a blood vessel by its contained blood
Blood Pressure (BP) is Expressed in millimeters of mercury (mm Hg)
What is the "opposition to flow"? Resistance
Resistance Measure of the friction between blood and the vessel walls
Resistance comes from 3 sources blood viscosity, total blood vessel length, blood vessel diameter
If Blood Pressure increases, blood flow _________ increases
if BP decreases blood flow_______
If resistance increases, blood flow¬¬¬¬¬________ decreases
Peripheral resistance is the most important factor influencing local blood flow
vasoconstriction (or vasodilation) can dramatically alter local blood flow, while the BP remains unchanged
Systemic Blood Pressure The pumping action of the heart generates blood flow (through the vessels along a pressure gradient, always moving from higher- to lower-pressure areas)
Systemic Blood Pressure results when flow is opposed by resistance
Three things about Systemic pressure Is highest in the aorta, Declines throughout the length of the pathway, Is 0 mm Hg in the right atrium
Arterial BP reflects two factors of the arteries close to the heart 1.Their elasticity (compliance or distensibility) 2.The amount of blood forced into them at any given time
Arterial Blood Pressure occurs in elastic arteries near the heart
Arterial BP is pulsatile (BP rises and falls)
systolic pressure When the left ventricle contracts, blood is forced into the aorta producing a peak in pressure (120 mm Hg)
Diastolic pressure pressure that occurs when the blood can not flow back into the heart and the aorta recoils (the diameter is smaller) (70-80 mm Hg)
Pulse pressure the difference between systolic and diastolic pressure
Mean arterial pressure (MAP) pressure that propels the blood to the tissues
Is Capillary BP low or high? low
Low capillary pressure is desirable because high BP would rupture the fragile, thin-walled capillaries
low capillary BP is sufficient to exchange between the blood and tissues
Venous BP steady and changes little during the cardiac cycle
The pressure gradient in the venous system is only about 20 mm Hg
A cut vein has ¬¬¬¬¬______blood flow; a lacerated artery flows even; in spurts
Blood pressure varies directly with changes in (2 things) blood volume and cardiac output
blood volume and cardiac output are determined mainly by (3 things) venous return, neural and hormonal controls
What two ways are Short-Term Mechanisms controlled? Neural Controls and chemical controls
Neural controls of peripheral resistance do two things 1. Alter blood distribution to respond to specific demands 2. Maintain MAP by altering blood vessel diameter
The vasomotor center a cluster of sympathetic nerons in the medulla that controls changes in the diameter of the blood vessels
Baroreceptors detect stretch  impulses to the vasomotor center, inhibits its activity and promotes vasodilation of arterioles and veins (Baroreceptor Reflexes)
Chemoreceptors detect a rise in CO2 content of the blood and stimulate the cardioacceleratory and vasomotor centers  increased cardiac output and vasoconstriction
The cortex and hypothalamus modify arterial pressure? via the medullary centers
Blood pressure is regulated by chemoreceptor reflexes sensitive to oxygen and carbon dioxide
Chemoreceptors sensitive to oxygen and carbon dioxide are found in the carotid and aortic bodies
Reflexes that regulate blood pressure are integrated in the medulla
Higher brain centers (cortex and hypothalamus) can modify BP via relays to medullary centers
Chemicals that Increase Blood Pressure Adrenal medulla hormones, Antidiuretic hormone (ADH), Angiotensin II, Endothelium-derived factors
Adrenal medulla hormones norepinephrine and epinephrine increase blood pressure
Antidiuretic hormone (ADH) causes intense vasoconstriction in cases of extremely low BP
Angiotensin II kidney release of renin generates angiotensin II, which causes intense vasoconstriction
Endothelium-derived factors promote vasoconstriction and are released in response to low blood flow
Chemicals that Decrease Blood Pressure Atrial natriuretic peptide (ANP), Nitric oxide (NO), Inflammatory chemicals, Alcohol
Atrial natriuretic peptide (ANP) causes blood volume and pressure to decline
Nitric oxide (NO) has brief but potent vasodilator effects
Inflammatory chemicals histamine, prostacyclin, and kinins are potent vasodilators
Alcohol causes BP to drop by inhibiting ADH
2 Long-Term Mechanisms (Renal Regulation) Direct Mechanism and Indirect renal mechanism
Long-term mechanisms control BP by altering blood volume
Increased BP (Direct Mechanism) stimulates the kidneys to eliminate water, thus reducing blood volume  dec in BP
Decreased BP (Direct Mechanism) stimulates the kidneys to increase blood volume and BP
Indirect renal mechanism involves the renin-angiotensin mechanism, a dec in BP  systemic vasoconstriction
Efficiency of the circulation can be assessed by taking pulse and blood pressure measurements
Vital signs pulse and blood pressure, along with respiratory rate and body temperature
Pulse pressure wave caused by the expansion and recoil of elastic arteries
Where is Radial pulse taken? on the radial artery at the wrist
How often is radial impulse used? routinely
Pulse varies with (3 things) health, body position, and activity
Systemic arterial BP is measured by what method? the auscultatory method
3 steps of the auscultatory method 1.A sphygmomanometer is placed on the arm superior to the elbow, 2. Pressure is increased in the cuff until it is greater than systolic pressure in the brachial artery, 3. Pressure is released slowly and the examiner listens with a stethoscope
Systolic pressure The first sound heard and is recorded
Diastolic pressure The pressure when sound disappears is recorded
The 2 Alterations in Blood Pressure Hypotension and Hypertension
Hypotension low BP in which systolic pressure is below 100 mm Hg
Hypertension condition of sustained elevated arterial pressure of 140/90 or higher
2 types of elevation in In Hypertension are Transient elevations and Chronic (persistent) elevation
In Hypertension, Transient elevations are normal
In Hypertension, Transient elevations can be caused by what 3 things fever, physical exertion, and emotional upset
Chronic (persistent) elevation is a major cause of (4 things) heart failure, vascular disease, renal failure, and stroke
3 types of Hypotension Orthostatic, Chronic, and Acute
Orthostatic hypotension temporary low BP and dizziness when suddenly rising from a sitting or reclining position
Chronic hypotension hint of poor nutrition and warning sign for Addison’s disease
Acute hypotension important sign of circulatory shock
What type of hypotension causes a threat to patients undergoing surgery and those in intensive care units? Acute hypotension
2 types of Hypertension Primary (essential) and Secondary
Hypertension may be ________ or _________ transient, persistent
Risk factors in primary hypertension include diet, obesity, age, race, heredity, stress, and smoking
Secondary hypertension is due to identifiable disorders, including excessive renin secretion, arteriosclerosis, and endocrine disorders
Blood flow (has another name) tissue perfusion
Blood flow, or tissue perfusion, is involved in (4 things) Delivery of oxygen and nutrients to, and removal of wastes from, tissue cells, Gas exchange in the lungs, Absorption of nutrients from the digestive tract, Urine formation by the kidneys
Blood flow is precisely the right amount to provide proper tissue function
2 things about Blood velocity 1.Changes as it travels through the systemic circulation, 2. Is inversely proportional to the cross-sectional area
Slow capillary flow (regarding blood velocity) allows adequate time for exchange between blood and tissues
Created by: Brina on 2003-07-16



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