vessels Flashcards
types of arteries
elastic
muscular
elastic arteries
walls have elastic CT
continue to push pressure, dont drop bp
get blood directly from heart
largest diameter of arteries, lowest resistance
muscular arteries
made of smooth muscle
smaller diameter than elastic
vessel types blood goes through in order (from heart)
elastic arteries muscular arteries arterioles capillaries venues veins
site of gaseous/nutrient exchange
capillaries
layers of capillaries
tunica interna only
layers of blood vessels
tunica interna
tunica media
tunica externa
tunica interna
superficial layer of vessel; lines lumen
made of simple squamous epithelium- v connected, v smooth (low friction)
tunica media
middle layer; made of smooth muscle (contractile)
how is tunica media different in arteries?
it is thicker and has elastic fibers
tunica externa
outer layer; has lots of collagen
anchors vessels in place
vasa vasorum
blood vessels in tunic external of v thick blood vessels (so far from lumen they cant get good enough supply!)
why does body want to constrict certain blood vessels sometimes?
make blood go a certain way or change bp in that area
capillaries
microscopic blood vessels with a diameter so small blood vessels have to go through single-file
3 types
pericytes
extra cells located along capillary that attach and stabilize capillary wall
(because cap wall is only t. interna)
3 types of capillaries
continuous
fenestrated
sinusoid
continuous capillaries
endothelial cells tightly joined; only fluids can pass through
fluids can also be exchanged by cells in wall (pinocytic vesicles)
most common type of capillary- found almost everywhere
continuous
where are fenestrated capillaries found
wherever there is absorption/filtration
endocrine organ, intestines, kidney
fenestrated capillary
cells of walls have “fenestrations” (pores) that are more permeable for increased exchange
doesnt allow big things through, though
where are sinusoidal capillaries found?
spleen, liver, bone marrow
sinusoidal capillaries
cell walls contain much larger pores called sinusoids
proteins and cells can pass through
components of capillary bed
terminal arteriole metarteriole thoroughfare channel post capillary venule vascular shunt true capillaries precapillary sphincter
terminal arteriole
delivers blood to capillary bed
metarteriole
arteriole side of vascular shunt
thoroughfare channel
venue side of vascular shunt
post capillary venule
receives blood from capillary bed
vascular shunt
“shortcut” how blood gets through capillary bed
true capillaries
rest of capillary bed (other than shunt)
there can be 10s or 100s of true capillaries
precapillary sphincter
regulatory structure that can open/close in each true capillary
T/F long distance running increases # of capillary beds
true
how can capillary beds function as microcirculation controller?
if tissue around cap bed needs more O2 or nutrients, we send more blood to those tissues by opening true capillaries and closing true capillaries in other areas
characteristics of arteries
thick walls small lumen thicker tunica media lower blood volume higher blood pressure no valves
characteristics of veins
thin walls larger lumen thinner tunica media higher blood volume lower blood pressure venous valves
venous valves
assist blood to get back to heart under low pressure
varicose veins
happen when blood pools if you stand in place too long too often
__% of blood is in veins at any given moment
65
3 vein modifications to help blood get back to heart under low pressure
- muscular pump
- respiratory pump
- valves
muscular pump of veins
aids in low pressure blood getting back to heart using skeletal muscle
muscle contraction pushes against blood vessel –> pushes blood forward
respiratory pump of veins
when chest expands when we breather, pressure difference increases so blood seeps into chest cavity
veins closest to heart in thoracic cavity have ___ bp
lowest
collateral channels
part of anastomoses
can be anywhere that needs increased blood supply
blood flow
volume of blood that flows through any part of body at any given time
constant through whole body but changes where to
blood flow is directly proportional to ____
differences in bp
higher difference in bp, more blood flows
blood flow is inversely proportional to ____
peripheral resistance
peripheral resistance
opposition to flow due to friction (more friction if smaller diameter)
of blood pressure and blood resistance, which is the major regulatory mechanism?
resistance
factors that affect peripheral resistance
blood viscosity
vessel length
vessel diameter
main factor that affects peripheral resistance
vessel diameter
blood viscosity
more elements in blood –> higher blood viscosity
cannot be changed in an instant
vessel length
longer blood vessels –> more resistance -> slower flow
cannot be changed in an instant
vessel diameter
increased diameter –> decreased resistance –> increased flow
can change quickly by sending nervous impulses to cause vasoconstriction or vasodilation
pulse pressure ___ as you go further from heart
narrows
pulse pressure is gone by ____
arterioles
blood pressure ____ as we move further from initial heartbeat
decreases
steepest drop in blood pressure occurs where?
arterioles
mean arterial pressure (MAP)
pressure that propels blood to tissues (more blood goes to areas with lower MAP)
MAP= diast. pressure + (pulse pressure/3)
most mechanisms that affect blood pressure control regulate changes in __-term
short
only long term blood pressure regulator
renal regulation
how to counteract brief bp fluctuations
alter blood distributions to respond to needs
alter vessel diameter
vasomotor center
altering blood distributions to respond to needs
how we change flow of blood through capillary bed
increase amount by opening true cap.; decrease by closing and flowing blood through vascular shunt
increase blood somewhere = increase bp
altering vessel diameter
dilation –> decreased bp; constriction –> increased bp
send nervous impulse to tunica media; vasomotor center sends sympathetic nerve fibers to cause vasoconstriction
when altering vessel diameter, how does body maintain same systemic bp?
localized change in bp is accounted for by opposite change somewhere else in body
vasomotor center
constant neural impulses coming from vasomotor center cause blood vessels to be partially constricted most of the time
allows for greater dilation when we need
reflex arcs
neural reflex arc
chemical reflex arc
neural reflex arc is based on
pressure difference
chemical reflex arc is based on
concentration difference
neural reflex arc
(if pressure incr)
- baroreceptors detect change in pressure as blood flows out of heart; sends signal to vasomotor center
- vasomotor center inhibited
- peripheral resistance decreases
- pressure drops
side effects of neural reflex arc
venous return drops cardiac output drops HR drops contractile force drops MAP drops
results of side effects of neural reflex arc
- low MAP initiates vasoconstriction and increased CO
- BP increases
chemical reflex arc
- chemoreceptors detect drop in O2 level or pH or increase in CO2
- cardioaccelatory center stimulated
- vasomotor center stimulated
- bp increases
detecting levels of certain chemicals can cause _________; release of certain chemicals can cause _________
auto regulatory event; change in bp
how do epinephrine and norepinephrine affect control of bp
vasoconstriction or vasodilation in response to certain stressors
can be neural or from adrenal medulla
how does ANP affect control of bp
if bp increases, pressure inside atria increases –> atria releases ANP
ANP causes increase urinary output –> changes blood volume, decreases bp
how does ADH affect control of bp
decreased bp causes hypothalamus to stimulate posterior pituitary to make ADH
ADH causes increased resorption in kidneys –> decreased urinary output –> increased bp
how does Angiotensin II affect control of bp
angiotensin II produced by renin from kidneys
causes vasoconstriction and change in resorption in kidneys
low bp causes renin to make angiotensin II which increases bp
how does endothelial-derived factors affect control of bp
blood vessels produce EDFs
EDFs are chemicals that change vessel diameter
some constrict some dilate
how does inflammatory chemicals affect control of bp
increases diameter of vessels (vasodilator)
Causes decreased bp and increased permeability of vessels
ex: histamine
how does alcohol affect control of bp
alc shuts off ADH production –> decreases blood volume and bp
inhibits vasomotor center –> vasodilation
causes direct dilation of vessesl
how does nicotine affect control of bp
increases bp
same effects as epi and norepi
renal regulation of blood pressure
alters blood volume, which changes bp
changing blood volume causes kidneys to eliminate H2O
increased bp means ____ loss of fluid from kidneys
increased
direct renal mechanism
increase in bp or blood vol speeds filtration rate in kidneys
indirect renal mechanism
decrease in bp causes kidneys to release renin
renin stimulates angiotensin ii production –> stimulates aldosterone production
aldosterone causes resorption of Na
bp increases
