Lesson 9 - Circulatory System: Blood Vessels and Circulation Flashcards
arteries carry blood…
away from the heart
arterioles
small branches of arteries
capillaries
connect the smallest arteries to the smallest veins to create a circuit
veins carry blood
back to the heart
venules
small branches that drain blood from capillaries, converge to form veins
tunica interna (tunica intima)
innermost layer of blood vessels, exposed to blood
what is the tunica intima made from? (2)
sse
endothelium - simple squamous epithelium
the tunica interna has a _____ _____ barrier
selectively permeable
the tunica interna secretes chemicals that do what? (2)
stimulate dilation or constriction of blood vessels
the tunica _____ normally repels blood cells and platelets to prevent clotting
interna/intima
when tissue around vessels is inflamed, _____ cells produce cell-adhesion molecules
endothelial cells
cell adhesion causes _____ to congregate in tissue where their action is needed
leukocytes
what separates the tunica interna from the tunica media?
internal elastic lamina
tunica media
middle layer of vessels
what is the tunica media made of? (3)
collagen, elastic tissue, and concentric sheets of smooth muscle
what separates the tunica media from the tunica externa?
external elastic lamina
what does the collagen, elastic tissue, and concentric sheets of smooth muscle do for blood vessels?
strengthens vessels and prevents blood pressure from rupturing them
tunica externa (tunica adventitia)
outermost layer of vessels
what is the tunica externa made of? (3)
loose connective tissue (collagen and elastic fibers); often nerges with that of neighboring blood vessels, nerves, or other organs
what does the tunica externa provide to the vessels? (2)
anchors vessels and provides a passage for small nerves and lymphatic vessels
vasa vasorum
“vessels of vessels”
- small vessels that supply blood to outer half of the wall in the larger arteries/veins
arteries and veins run…
side by side
arteries have…(2)… than veins
- thicker walls
- higher blood pressure
a collapsed artery has…(2)… lumen
a small, round
- pleated/rippled
veins have a…(2)…lumen
large, flat, deflated
veins are more _____ and can stretch more
distensible/expandable
_____ lining contracts while _____ lining does not
vein, artery
veins have _____ to prevent backflow
valves
arteries are more _____ than veins
elastic - stretches at higher pressure
what does the elasticity of arteries allow?
to absorb pressure waves that come with each heartbeat
arteries change _____ which is controlled by the _____ division of the ANS
diameter, sympathetic
do arteries have dual innervation of the sympathetic and parasympathetic nervous system?
no! only sympathetic
arteries have autonomic tone, meaning…
it has background levels of stimulation from the sympathetic system
vasoconstriction
the contraction of arterial smooth muscle by the ANS that constricts the lumen
vasodilation
the relaxation of arterial smooth muscle that enlarges the lumen
vasoconstriction/dilation affect (3)
a.p.c.
- afterload on the heart
- peripheral blood pressure
- capillary blood flow
vasoconstriction _____ afterload
increases
arteries are divided into three classes by size
c.d.r.
- conducting (elastic/large)
- distributing (muscular/medium)
- resistance (small)
conducting (elastic/large) arteries
largest arteries
examples of conducting arteries (5)
aorta, common carotid, subclavian, pulmonary trunk, and common iliac arteries
conducting arteries have this at the border between the tunica interna and media
internal elastic lamina
conducting arteries have this between the tunica media and externa
external elastic lamina
conducting arteries _____ during systole, and _____ during diastole
expand, recoil
elasticity of arteries does what to pulse force?
evens it out
expansion of conducting arteries does what for smaller downstream arteries?
takes pressure off of them
what does the recoil of conducting arteries do for circulation?
it helps maintain pressure during the relaxation phase, keeping blood moving
distributing (medium/muscular) arteries
where do they distibute blood?
distribute blood to specific organs
examples of distributing arteries (4)
b.f.r.s.
brachial, femoral, renal, and splenic arteries
in distributing arteries, what takes up three fourths of the wall thickness?
smooth muscle layers
on distributing arteries, what layers are notably thick? (2)
internal and external elastic laminae
resistance arteries have a thicker tunica _____ and very little tunica _____
media, externa
arterioles
smallest of the resistance arteries
arterioles have thin/incomplete tunica _____, and little to no tunica _____
media, externa
what controls the amount of blood going to various organs?
arterioles
with what stimulation does artery diameter change? (2)
sympathetic or endocrine stimulation
constricted arteries do what to blood flow?
opposes it, creates resistance
where does most peripheral resistance occur?
arterioles/resistance vessels
metarterioles (thoroughfare channels)
short vessels that link arterioles directly to venules in some places, providing a shortcut for blood t bypass capillary beds
aneurysm
weak point in artery or heart wall that forms a thin-walled, bulging sac that pulsates with each heartbeat (may rupture at any time)
dissecting aneurysm
blood accumulates between tunics of artery and separates them
what usually causes a dissecting aneurysm
degeneration of the tunica media
most common sites for aneurysms (3)
aa.ra.ac.
abdominal aorta, renal arteries, and arterial circle at the base of the brain
how do aneurysms cause pain?
putting pressure on other structures
what are the most common causes of aneurysms? (2)
a.h.
atherosclerosis and hypertension
aneurysms are the result of… (3)
cw.t.bi.
congenital weakness of blood vessels, trauma, or bacterial infections
sensory structures in some major vessel walls do what?
monitor blood pressure and chemistry and transmit that info to regulate heartbeat, blood vessel diameter, and respiration
carotid sinuses
baroreceptors in the walls of the internal carotid arteries
what do carotid sinuses do?
they monitor blood pressure
how do carotid sinuses transmit signals to the brain?
through the glossopharyngeal nerve
what structure helps create the baroreflex?
carotid sinuses
carotid bodies
chemoreceptors/oval bodies near the branches of the common carotids
what do carotid bodies monitor?
blood chemistry
how do carotid bodies transmit info to the brain?
through the glossopharyngeal nerve to the brainstem respiratory centers
what do carotid bodies do to help stabilize blood chemistry?
they adjust respiratory rate to stabilize pH, CO2, and O2
aortic bodies
one to three chemoreceptors in the walls of the aortic arch
what nerve innervates the aortic bodies?
vagus
aortic bodies are just like what in structure and function?
carotid bodies
capillaries are _____ vessels, meaning they…
exchange; they are where gasses, nutrients, wastes, and hormones pass between the blood and tissue fluid
microcirculation/microvasculature consists of…(3)
capillaries, arterioles, and venules
nearly every cell in the body is close to a _____
capillary
where are capillaries not found? (5)
- tendons
- ligaments
- epithelium
- cornea
- lens
what are capillaries composed of? (2)
e.b.
endothelium and basal lamina
three capillary types distinguished by permeability
- continuous
- fenestrated
- sinusoids
where are continuous capillaries found?
in most tissues
continuous capillaries
endothelial cells held together by tight junctions forming a continuous tube with cells separated by gaps
intercellular clefts
small gaps between the endothelial cells of continuous capillaries
what kind of solutes can pass through intercellular clefts?
small solutes like glucose
what types of solutes cannot pass through intercellular clefts? (3)
most plasma proteins, and other large molecules like blood cells and platelets
basal lamina
thin protein-carbohydrate layer that surrounds the outer endothelium
capillaries lack what portions of vessels? (2)
tunica media and externa
pericytes
wrap around the capillaries and contain the same contractile protein as muscle to regulate blood flow
pericytes can differentiate into _____ cells, and can do what?
endothelial cells; help with vessel growth and repair
where are fenestrated located?
found in organs that require rapid absorption or filtration
examples of places you’d find fenestrated capillaries (3)
- kidneys
- small intestine
- choroid plexus of the brain where cerebrospinal fluid is produced
fenestrated capillaries
their endothelial cells contain filtration pores, or fenestrations
what do fenestrated capillaries allow to pass?
only small molecules, no large things like proteins
fenestrated capillaries are spanned by what?
a very think glycoprotein membrane much thinner than the cell’s plasma membrane
sinusoidal capillaries/sinusoids
endothelial cells are separated by WIDE gaps with no basal lamina, often have large fenestrations
where can you find sinusoids/sinusoidal capillaries? (4)
in irregular blood-filled spaces of the liver, bone marrow, spleen, or endocrine organs
what do sinusoids allow to pass? (3)
large proteins like albumin, clotting factors, and new blood cells to enter circulation
what are sinusoids monitored by? what do they do?
phagocytic cells to engulf damaged RBCs, pathogens, and cellular debris
what are capillary beds supplied by?
usually a single arteriole or metarteriole
where do capillaries drain?
venules or distal ends of metarterioles
at any given time, _____% of the body’s capillaries are shut down
75
most control over capillaries involves what?
constriction of upstream arterioles
precapillary sphincters
control flow in capillary beds supplied with metarterioles
when precapillary sphincters are relaxed…
capillaries are well perfused with blood
when precapillary sphincters contract…
they constrict the entry to the capillary and blood bypassee them
vasomotion
contraction and relaxation cycle of precapillary sphincters
what does vasomotion do to blood in capillaries?
causes the blood flow in capillary beds to be a constantly changing route
vasomotion is controlled locally by what?
changing concentrations of chemicals and dissolved gases in interstitial fluid - AUTOREGULATION
veins are the _____ vessels of the cardiovascular system
capacitance
which vessels are thin-walled, flaccid, collapse when empty, and expand easily?
veins
which vessels have a greater capacity for blood containment?
veins
which vessels have a steady blood flow?
veins
where is most blood located at any given moment?
veins
which vessels are subjected to relatively low blood pressure?
veins
types of veins (4)
p.m.m.l.
- postcapillary veins
- muscular veins
- medium veins
- large veins
postcapillary veins
smallest veins that emerge from the ends of capillaries
what vessels are even more porous than capillaries?
postcapillary venules
postcapillary venules consist of what structural portions of a vessel? (3)
- tunica interna
- few fibroblasts around it
- no muscle
muscular veins
receive blood from postcapillary venules
muscular veins consist of what structural portions of a vessel? (2)
- one or two layers of smooth muscle in the tunica media
- thin tunica externa
medium veins consist of what structural portions of a vessel? (3)
- thin tunica media
- thick tunica externa
- tunica interna forms venous valves
what propels venous blood back to the heart?
the skeletal muscle pump
failure of venous valves can cause…
varicose veins
large veins consist of what structural portions of a vessel?
- smooth muscle in all three tunics
- thinish tunica media, moderate smooth muscle
- tunica externa is thickest layer w/ longitudinal bundles of smooth muscle
examples of large veins (4)
venae cavae, pulmonary veins, internal jugular veins, renal veins
what happens to blood in the lower legs of people who stand for long periods of time?
blood pools stretching the veins, causing the cusps of valves to pull apart further weakening the vessels
varicose veins
veins with irregular dilations due to weakening, where blood backflows and further distends the vessels
what are hemorrhoids?
varicose veins of the anal canal
what things cause increase risk of varicose veins? (3)
- hereditary weakness
- obesity
- pregnancy
simplex and most common route for blood (6)
heart -> arteries -> arterioles -> capillaries -> venules -> veins
anastomosis
convergence between two vessels other than capillaries
arteriovenous anastomosis (shunt)
artery flows directly into veins, bypassing capillaries
venous anastomosis
one vein empties into another
arterial anastomosis
two arteries merge, providing collateral routes of blood supply
what is the most common type of anastomosis?
venous
explain the difference between a metarteriole and an arteriovenous anastomosis
metarterioles are artery/vein junctions that occur when capillaries are ‘closed’, while an arteriovenous anastomosis is a artery/vein shunt that is constantly in use (not connected to capillaries)
capacitance
blood vessels ability to stretch
high capacitance
expands easily at low pressure
low capacitance
expands only at high pressure
_____ stretch more than _____, and are called capacitance vessels
veins, arteries
flow
amount of blood flowing through and organ, tissue, or blood vessel at any given moment
at rest, total flow is… (2)
quite constant and equal to cardiac output
hemodynamics
the physical principles of blood flow based on pressure and resistance
flow equation
deltaP/R
- deltaP = difference in pressure between one area and another
- R= resistance against blood flow
the greater the pressure difference between two points, the _____ the flow; the greater the resistance, the _____ the flow
greater, less
pulse pressure
difference between systolic and diastolic pressure
why is pulse pressure important?
important measure of the driving force on circulation and of stress exerted on small arteries by pressure surges generated by the heart
mean arterial pressure (MAP) equation
diastolic pressure + (1/3)pulse pressure
syncope
fainting/passing out
since pressure varies across the cardiac cycle, blood flow in arteries is _____
pulsatile
blood spurts intermittently from an open _____
artery
bleeding from _____ tends to be slow and steady
veins
BP tends to rise with _____
age
ateriosclerosis
stiffening of arteries due to deterioration of elastic tissue of artery walls
atherosclerosis
build up of lipid deposits that become plaques
hypertension
chronic resting blood pressure higher than 130/80
what can hypertension cause in the body? (3)
weaken arteries, cause aneurysms, and promote atherosclerosis
hypotension
chronic low resting blood pressure - no specific numerical criterion
what is hypotension caused by?
b.a.d.
blood loss, dehydration, anemia
blood pressure is determined by three variables
c.b.r.
- cardiac output
- blood volume
- resistance to flow
blood volume is regulated mainly by the _____
kidneys
peripheral resistance
opposition to flow that blood encounter in vessels away from the heart
resistance hinges on three variables
- blood viscosity
- vessel length
- vessel radius
blood viscosity stems mainly from… (2)
a.r.
plasma proteins (albumin) and RBCs
these reduce viscosity of blood and speed up flow (2)
- anemia
- hypoproteinemia (low albumin)
these increase viscosity and flow declines (2)
p.d.
- polycythemia
- dehydration
the farther liquid travels through a tube, …
the more cumulative friction it encounters
_____ and _____ decline with distance
pressure, flow
what has the greatest control over blood flow?
vessel radius
_____ changes in the radius results in _____ changes in blood flow
small, large
blood exhibits laminar flow, meaning…
it flows in layers, and a dilating vessels allows more blood to flow without more of it making contact with the vessel wall, speeding up flow
vasomotion is controlled by…
the vasomotor center in the medulla
blood velocity decreases from aorta to capillaries for three reasons
- friction has reduced the speed over distance traveled
- the smaller radii of arterioles/capillaries provide more friction
- number of vessels and their total cross-sectional area becomes greater
from capillaries to vena cava, velocity increased again to due…(2)
- veins are larger, they create less resistance than capillaries
- large amounts of blood from the capillaries are forced into smaller channels (veins)
does blood regain the same velocity it had in large arterioles? why or why not?(3)
NO
- veins are further from pumping heart
- veins are more compliant (stretchy)
what are the most significant point of control over peripheral resistance and flow?
arterioles
why are arterioles so integral to peripheral resistance and flow? (3)
- on proximal side of capillary beds, best positioned to regulate flow
- outnumber any other type of artery, providing the most numerous control points
- more muscular in proportion to diameter
what vessels produce half the total peripheral resistance?
arterioles
resistance vessels
arterioles
