The Cardiovascular System 4 Flashcards
what are the three layers of a blood vessel
tunica intima, tunica media, and tunica externa
what is the tunica intima
innermost layer of blood vessel
endothelium made of simple squamous epithelium
also has a layer of areolar connective tissue
what is the tunica media
middle layer of circular smooth muscle and elastic fibers
performs vasoconstriction and vasodilation
what is the tunica externa
outermost layer of blood vessel
made of areolar connective tissue with elastic and collagen fibers
anchors vessel to other structures
what are vasa vasorum
smaller arteries coming off of a blood vessels
required to supply very large vessels
what are the three types of arteries
elastic (conducting)
muscular (distributing)
arterioles
what are elastic (conducting arteries)
largest type of artery
arteries that exit from heart chambers
made of little smooth muscle fibers but lots of elastic fibers stretch and recoil to propel blood
what are muscular (distributing arteries)
medium arteries that have more smooth muscle
vasodilation and vasoconstriction
mostly named arteries
what are arterioles
smallest arteries
smallest ones have thin endothelium and single smooth muscle layer
regulates systemic blood pressure and flow
what is atherosclerosis
thickening of tunica intima due to the buildup up atheroma; narrowing of lumen
caused by: trauma, high blood pressure, hypercholesterolemia (too much blood cholesterol)
define rouleau
erythrocytes move in a single file line in capillaries
what are the three types of capillaries
continuous
fenestrated
sinusoid
explain the components of a capillary bed
arteriole on one end and postcapillary venule the other
metarteriole: branch off of arteriole; proximal portion has smooth muscle
thoroughfare channel: branch off venule
true capillaries: branches off metarteriole and thoroughfare channel; where gas exchange happens
define perfusion
amount of blood entering capillaries per unit time per gram of tissue
where is most of the blood found in vessels
veins
they act as blood reservoirs (70%)
what is an arterial or venous anastomosis
two or more arteries or veins converge to supply same region
what is an arteriovenous anastomosis
shunt that transports blood from artery directly to vein
found in areas like fingers
what is a portal system
two capillary beds separated by a portal vein
what is a cross-sectional area
area of cross section of one vessel
what is total cross-sectional area
sum of diameters of all vessels of a certain type
why is it good that blood flow is slow in capillaries
so there is time for exchange between blood and tissue fluid
how does diffusion in capillaries work
substances leave or enter blood depending on concentration gradient
oxygen, hormones, and nutrients move from blood into interstitial fluid
wastes diffuse from tissues to blood
small particles will go through endothelial cells
large particles will go through gaps in sinusoids
how does vesicular transport in capillaries work
substances are taken in by pinocytosis and transported across cell
substances are secreted by exocytosis
used for substances that are too big to move through membranes
how does bulk flow in capillaries work
fluids flow down pressure gradient
includes filtration and reabsorption
how does filtration in a capillary work
occurs at arterial end
fluid moves down its pressure gradient: out of blood and into interstitial fluid
blood hydrostatic pressure is greater than net osmotic pressure (net pressure out)
how does reabsorption in a capillary work
occurs at venous end
fluid moves down its pressure gradient: from interstitial fluid back into blood
net osmotic pressure is greater than blood hydrostatic pressure (net pressure in)
define hydrostatic pressure
forced exerted by a fluid
two types: blood and interstital pressures
define blood hydrostatic pressure
force exerted per unit area by blood on vessel wall
high at arterial end which promotes filtration
define interstitial fluid hydrostatic pressure
force of interstitial fluid on outside of blood vessel
around 0 usually
define colloid osmotic pressure
pull on water due to presence of proteins (colloid)
two types: blood and interstitial fluid colloid pressures
define blood colloid osmotic pressure (oncotic pressure)
draws fluid into blood due to blood proteins
higher than hydrostatic pressure which promotes reabsorption at venule end
define interstitial fluid colloid osmotic pressure
draws fluid into interstitial fluid
relatively small becuase only small amount of proteins in interstitial fluid
define net filtration pressure and give equation
difference between net hydrostatic pressure and colloid osmotic pressure
NFP = (HPb - Hpif) - (COPb - COPif)
higher at arterial end (filtration)
lower at venous end (reabsorption)
what is the role of the lymphatic system in capillary exchange
lymphatic system picks up excess fluid not reabsorbed at venous end and returns it to venous circulation
15%
what is local blood flow and what are the four things it is dependent on
some capillaries are filled, some are not
degree of tissue vascularity
myogenic response
local regulatory factors altering blood flow
total blood flow
define degree of vascularization
extent of vessels in a tissue
tissues that are more metabollically active have more vessels to get them more nutrients and vise versa
ex. brain tissue has more vasculature than tendons
define angiogenesis
formation of new vessels to increase perfusion
ex. in adipose tissue during weight gain
define regression
returning to previous state of blood vessels
ex. when adipose tissue is lost
what is the myogenic response
smooth muscle of a vessel and its ability keep local blood flow constant by dilating and constricting as need be
if blood pressure rises, vessels will stretch (vasoconstriction to return it to its normal size)
if blood pressure decreases, vessels will stretch less (relaxation to return to normal size)
what is autoregulation
how the tissue controls local blood flow based on need
if tissue activity increases, stimuli signal inadequate perfusion and act has vasodilators
which local substances act as vasodilators to increase blood flow
increased CO2, hydrogen, potassium, lactate
decrease in oxygen and nutrient levels
bradykinin
nitric oxide
what are vasodilators
a type of vasoactive chemical that dilates arterioles and relax precapillary sphincters to increase flow to capillary beds
what is the local, short term regulation for inflammed tissue
tissue, leukocytes, and platelets release vasoactive chemicals like histamine, bradykinin, and nitric oxide which cause arterioles to dilate
define total blood flow and give equation
amount of blood transported through vasculature per unit of time
equal to cardiac output
F = changeP / R
changeP = systemic blood pressure gradient
define blood pressure
force of blood against vessel wall
define pulse pressure
pressure in arteries added by heart contraction
difference between systolic and diastolic blood pressure
ex. 120/80 = 40 PP
define mean arterial pressure and give equation
average arterial blood pressure across entire cardiac cycle
MAP = diastolic pressure + 1/3rd PP
provides index of perfusion
higher in arteries, lower in veins
what are the three things that affect resistance (peripheral resistance)
blood viscosity (n), vessel length (L), and vessel lumen diameter (r^4)
what is the resistance equation
R = 8 x n x L / pie x r^4
define peripheral resistance
resistance of blood in blood vessels
define viscosity
resistance of fluid to its flow
goes up due to more particles in blood
goes down due to anemia
what are the three areas of the cardiovascular control center in the medulla
cardioinhibitory center, cardioacceleratory center, and vasomotor center
what are companion vessels
vessels that lie next to each other and supply the same region
ex. an atery and vein supplying the same area will run together but will flow in opposite directions typically
what are some unique functions of ateries
thick tunica media, smaller lumen
more elastic and collagen fibers that make them springy and resilient
what are some unique features of veins
have a thicker tunica externa, wider lumen
less elastic and collagen fibers so they’re flat in the absence of blood
what are some unique features of capillaries
only have a tunica intima (endothelelial and basement membrane layer)
thin to allow for rapid gas exchange
define vasomotor tone
smooth muscle is arterioles is usually somewhat constricted
explain an angioplasty
used to treat atherosclerosis
catheter put artery, balloon is inflated, stent is placed
what is an aneurysm
part of an arterial wall thins and balloons out
can rupture
risk increases with age
most common around brain
what is a precapillary sphincter
rings of smooth muscle at base of true capillaries coming off metarteriole
relaxation: allows blood to flow through for gas exchange
constriction: sends blood through metarteriole to thoroughfare channel
define vasomotion
cycle of contracting and relaxing precapillary sphincters
define net hydrostatic pressure
difference between hydrostatic pressure of blood and interstitial fluid
define net colloid osmotic pressure
difference between blood and interstital fluid osmotic pressures
define tumor angiogenesis
tumors trigger new growth of blood vessels to feed their cells
what are vasoconstrictors
a type of vasoactive chemical that constricts arterioles and cause contration of precapillary sphincters to decrease flow into capillary beds
what is the local, short term regulation for damaged tissue
leukotrines and thromboxanes are released which vasoconstrict vessels to prevent blood loss through damaged vessel
define cerebral edema
excess interstitial fluid in the brain
occurs if mean arterial pressure is greater than 160 mmHg
high pressure increases filtration (more fluid is leave the blood for the tissues; leads to excess fluid)
what are some features of capillary blood pressure
no systolic and diastolic - flow and pressure are smooth
arterial end: 40 mmHg
venous end: 20 mmHg
what are the three things venous return depends on
pressure gradient (small)
skeletal muscle pump
respiratory pump
explain the skeletal muscle pump in terms of venous return
muscle contracts, vein is squeezed
blood is pushed towards the heart
valves in veins prevent backflow
explain respiratory pump in terms of venous return
brings blood back towards the heart
inspiration: diaphragm contrats, abdominal pressure increases and drives blood towards thoracic cavity
expiration: diaphragm relaxes, abdominal pressure decreases, blood is driven towards heart
explain vericose veins
dilated and tortuous, nonfunctional veins
blood pools here
usually in lower legs
called hemorrhoids if they’re in the anorectal region
explain circulatory shock
insufficient blood flow to prefuse tissues
causes: impaired heart, low venous return
define resistance
the friction blood encounters
what are the three things that blood pressure is dependent on
cardiac output
resistance to blood flow
blood volume
(all directly related)
how does the vasomotor center affect blood pressure
sympathetic: increase in blood pressure
increased peripheral resistance: blood vessels constrict
larger circulating blood volume: blood moves from venous reservoirs
redistribution of blood flow: more blood to heart and skeletal muscle
opposite for parasympathetic
explain how baroreceptors affect regulation of blood pressure
located in aortic arch and carotid sinus
arch: communicates to cv center through vagus nerve
carotid sinus: communicates to cv center through glossopharyngeal nerve (more sensitive to changes than arch)
blood pressure decrease: baroreceptors fires less, signals sympathetic pathways in cv center to increase cardiac output and blood pressure
blood pressure increase: baroreceptor fires more (more stretch), more signals along parasympathetic pathways , less cardiac output and blood pressure
give an example of how chemoreceptors affect blood pressure
if too much CO2 is detected, they will signal to the cv center, cv center will increase blood pressure to get the blood to the lungs to breath it off
how does the hypothalamus regulate blood pressure
increases cardiac output and resistance
how does the limbic system affect blood pressure
alters blood pressure in response to emotions or memories
explain the renin-angiotensin-aldosterone system (RAAS)
low blood pressure detected:
angiotensinogen made by the liver is released into blood
renin made by kidneys released into blood
renin converts angiotensinogen into angiotensin 1
angiotensin-converting enzyme (ACE) converts angiotensin 1 to angiotensin 2
angiotensin 2 raises blood pressure
how does angiotensin 2 raise blood pressure
vasoconstricts
stimulates thirst center
decreases urine formation
stimulates release of aldosterone and antidiuretic hormone
how does aldosterone work to maintain blood volume and pressure
released from adrenal cortex due to angiotensin 2
increases absorption of ions and water in kidney to decrease urine output
how does antidiuretic hormone help to elevate blood pressure
released from posterior pituitary because of signals from hypothalamus
increases water reabsorption in kidney
stimulates thirst center
vasoconstriction
how does atrial natriuretic peptide (ANP) decrease blood pressure
released from atria when they are stretching
stimulates vasodilation
increases urine output
what is hypertension
elevated blood pressure
greater than 140/90
can damage vessels
what is hypotension
low blood pressure
less than 90/60
define orthostatic hypotension
drop in blood pressure upon standing suddenly
