blood vessels chp 21 Flashcards
how many layers do both arteries and veins have
3 layers
1. tunica intima (tunica interna)
- tunica media
- tunica externa (tunica adventitia)
tunica intima (tunica interna)
innermost layer with endothelial cell lining with underlying CT layer
tunica media
middle layer made of concentric sheets of smooth muscle, encircling blood vessels
tunica externa (tunica adventitia)
outermost layer
CT sheath with collagen and elastic fibers
arteries structure
round with a thick wall
- tunica intima has internal elastic membrane so they can expand (veins dont)
- tunica media is much thicker in arteries with elastic fibers
-tunica externa is similar in arterties and veins
vein structur
flattened / collapsed with thin wall
- tunica media is much thinner and has collagen
-tunica externa is similar in arterties and veins
what are the 3 types of capillaries and what does a regular capillary consist of
consists of a basement membrane (basal laminate) and 1 cell layer thick endothelium
- continuous capillaries
- fenestrated capillaries
- sinusoid capillaries
continuous capillaries
endothelium form complete lining
-least permeable / restricted and regulated
- most common
- skin/muscle
fenestrated capillaries
allows for rapid exchange of water and solutes
- pores/windows in endothelial lining
- in active areas of absorption / filtration
- in the kidney and small intestine
sinusoid capillaries
most permeable
- free exchange of water and large solutes
- in special locations such as liver, bone marrow, and spleen
where do capillaries function in
in interconnected networks (beds) inbetween arteries and veins
collateral arteries allow for
capillary beds to receive blood from more than 1 artery
a single arteriole gives rise to dozens of capillaries by way of
met arterioles
thoroughfare channels are where ____ flows into capillaries with a ____
blood flows into capillaries with a precapillary sphincter
capillary hydrostatic pressure (CHP)
blood pressure within capillary beds
- drives force for filtration
-pushes water and molecules out of bloodstream and into interstitial fluid
filtration allows for ___ solutes to cross endothelium and ___ ones do not
small solutes ; larger ones do not
what determines net filtration pressure (NFP)
CHP - BCOP
(capillary hydrostatic pressure - blood colloid osomotic pressure)
high BCOP and low CHP leads to
reabsorption
- fluid movesinto capillary
low BCOP and high CHP
filtration
- fluid is forced out of capillary
NFP = 0 means
no net movement of fluid
CHP = BCOP
blood pressure
force that blood exerts against a vessel wall
systolic pressure
peak arterial pressure during ventricular contraction
diastolic pressure
minimum arterial pressure during ventricular relaxation (between beats)
pulse pressure
difference between systolic and diastolic pressure
what is the pulse pressure for 110/60
50
systolic/diastolic
Mean arterial pressure (MAP)
mean pressure of readings taken at intervals of cardiac cycle
- varies w. gravity
expansion and recoil of conducting arteries help maintain ….
steady flow of blood
hypertension
high BP
hypotension
low BP
in the systemic circulation, systolic and diastolic pressures are ___ and have less range ____ from left ventricle
lower + have less ranger further away from left ventricle
what are the 3 physiological factors that determine blood pressure
- cardiac output
- blood volume
- resistance to flow (peripheral resistance)
cardiac output
amount of blood ejected in 1 min
blood volume is regulated by the
kidneys
more volume = ___ pressure
more pressure
resistance to flow is determined by
blood viscosity , vessel length, vessel diameter
- vessel diameter is the biggest factor and length
in a small diameter vessel, blood is slowed so resistance is ___
high
blood flow is directly proportional to BP between how many points
2
blood flow is inversely proportional to
peripheral resistance
if resistance increases blood flow ___
decreases
does pressure or resistance have a greater affect on flow?
resistance
when P increases flow, ___
speeds up/ increases
longer blood vessel means greater surface area with bloodd so resistance is
greater
name of high pressure system which is 13% of total blood volume
systemic arterial system
systemic venous system
very low pressure system
- needs valves to prevent backflow
- skeletal muscle contraction and thoracic pump help overcome force of gravity
- makes up 64% of total blood volume
is there is a change in 1/3 factors that determine BP what happens
compensated by changing other variables
short term regulation of BP
nervous system + hormones adjust BP by changing peripheral resistance and CO
long term regulation of BP
blood volume is altered in the kidneys
what are the 2 mechanism of BP control
- local autoregulation (blood flow in local areas)
- central regulation (neural and endocrine) widespread
what happens if autoregulation doesnt work?
neural and endocrine mechanisms take over
explain the endocrine response at kidneys to low BP and volume, what are the prime hormones involved
kidneys act directly + indirectly to regulate arterial pressure and control BP long term
directly - w/o hormones
indirectly- renin-angiotensin-aldosterone
( constrict blood v, stimulate thrist, hold on to water via adh, hold on to Na+ via aldestrone)
renal mechanisms mediate ___ term regulation of BP by altering what?
mediate long term regulation of BP by altering blood volume
decreased blood volume = ___ BP
decreases
what hormones are released via kidney (renal) when BP is low
renin
EPO
ACE
short term regulation of BP hormonally via
changes in peripheral resistance
short term hormones to regulate BP
adrenal medulla hormones (E + NE) = vasoconstriction
angiotensin II = vasoconstriction
ANP (atrial natriuretic peptides)= vasoconstriction
ADH(vasopressin)= vasoconstriction only in severed cases of low BP
vasoconstriction
narrow/ constricting blood vessels
