ch 19- The Cardiovascular System: Blood Vessels 2-4 Flashcards
blood vessel walls the 3 layers
tunica intima, media, externa
tunica intima
innermost layer of blood vessel, endothelium and simple squamous cells, provides slick surface to make blood flow easier by reducing friction and resistance
capillaries have
only endothelium and basement membrane
tunica media
middle layer of vessel wall, contains smooth muscle, thicker in arteries than veins, maintains BP and circulation. veins have thinner tunica media
vasoconstriction
smooth muslce contracts, lumen smaller
vasodilation
muscle relaxes, lumem larger
lumen
general term for any empty space, smith travels through it
tunica externa
outermost vessel wall, has collagen fibers, protects vessel, anchors blood vessels to structures, withstands stretch and prevents breaks
vasa vasorum
larger vessels have this, blood vessel on a blood vessel. larger arteries have walls that are too thick and needs smaller ones for nutrients to enter
arteries
branches several times to make smaller vessels. carry blood away from heart
systemic- oxygenated blood is carried
pulmonary arteries- oxygen poor blood
elastic arteries/conducting arteries
pulmonary trunk and aorta branch with brachiocephalic, left carotid, left subclavian. conducts blood away with large lumen, making resistance less and blood conduction easier.
elastic arteries have
a lot of elastin, walls can expand and recoil as heart pumps blood in, allowing for blood to flow smooth and relaxes heart
muscular arteries
distributing arteries, branches off elastic arteries, good for vasoconstriction and dilation. thicker tunica media, less elastic quality but good for that
arterioles
resistance arteries, smallest ones, flow into capillary beds directly. vasoconstriction and vasodilation controls how much blood goes into capillary bed. less blood is less blood in capillaries.
capillaries
exchange vessels, directly contact tissue allowing for gas exchange and waste removal, squeeze thru single file bc they are so small. joined by tight junctions, but have intracellular clefts that help permeability
intracellular clefts
small open spaces where fluids and smack solutes pass, these are not in brain capillaries bc they need to minimize movement of stuff.
wall of capillary is simple squamous epithelia, how is that beneficial
increases the rate of exchange
continuous capillaries
most common, least permeable, uninterrupted wall no extra holes or pores. water and ions pass, in skin and skeletal tissue
fenestrated capillaries
walls have pores, more permeable, found where absorption and filtration are frequent. small intestine and kidneys. increases rate of exchange, larger things can pass through buy selective. no RBC or proteins
sinusoid capillaries
least common, most permeable. large inrtracellular clefts and large lumen. giant pores holes and wider. WBC and RBC can pass through. ex liver bone marrow spleen
microcirculation
flow of blood through capillary bed. artery to capillary bed to venule.
terminal arteriole rich
branches to form network of capillaries. arteriole pressure controls blood flow. capillary bed empties into post capillary venule. rich red to o2 poor blue
venules r
oxygen poor and nutrient poor, waste rich blood.
veins
from capillary beds smaller veins combine to form larger beds. carry blood to heart
systemic- carry oxygen poor blood
pulmonary- oxygenated blood
venule veins
lead from capillary bed to larger veins
porous and easy passage to and from bloodstream. more permeable.
veins
thinner tunics, larger lumen. less tissues in walls, larger lumen allows for more blood to be stored in blood reservoirs temporarily.
why does low pressure in veins create an issue
can impair blood flow, blood could stop but balance is possible!
physiology of circulation
blood flow, blood pressure, resistance
blood flow
volume of blood flowing through a vessel, organ, or entire circulation in a period. flows high to low. if an organ doesn’t need blood, vessels serving that organ constrict, then once blood needed, would dilate.
hydrostatic pressure difference
must exist for blood flow to occur. drives blood flow force, arteries have higher pressure because more smooth muscle and tissue is there. example- equalizing that pressure of heart would stop blood flow in heart
blood pressure
force exterted on blood vessel wall by blood it contains. like water balloon. blood pushes against it, highest pressure in aorta bc its closest to the heart and propels the furthest distance.
how blood pressure changes as blood goes from artery to capillary to vein
pressure decreases along the way
arterial blood pressure
indicator better than veins, doctors r concerned with this
resistance
opposition of blood flow thru a vessel bc of friction between vessel wall and blood flowing. peripheral resistance is the highest in systemic circulation.
3 reisstance sources
blood viscosity- more viscous nis more pressure bc of resistance in vessel
vessel legnth- longer means more wall of vessel so more resistance exists
vessel diameter- smaller diameter means greater resistance smaller tube blood in more contact so more resistance
which factor of resistance can be changed
vessel diameter
how do changes in blood pressure and resistance affect blood flow
hydrostatic pressure increases, blood flow increases
resistance increases, blood flow decreases . more blood rubs vessel wall.
systemic blood pressure
pumping action of heart generates blood flow, blood pressure results when blood flow is opposed by resistance of blood vessels.
arterial blood pressure
blood pressure in aorta is pulsatile, rises and falls in fashion. affected by distensibility of vessel walls and by blood volume
distensibility of blood vessel walls, degree of stretch of blood vessels
less elasticity means higher pressure
volume of blood pumped into arteries
higher blood volume means more blood pressure
systolic and diastolic
pressure of contraction, pressure when heart relaxes. when it relaxes, still need pressure to move blood.
normal BP
90-120 over 70-80
pulse pressure
systolic minus diastolic, normal is 40 Hg. represents force the heart generates with each contraction. higher pressure means heart is working harder to pump blood.
capillary blood pressure
low blood pressure typically, important bc need low pressure bc walls bust open if not. steepest drop in pressure is in arterioles bc once it gets to capillary it wants that low pressure
venous blood pressure
bp generally low, but low pressure in veins would prevent efficient blood return.
how to solve venous BP that is low
skeletal muscle- contracts muscles to squeeze veins and push blood forward
large diameter lumen- larger diameter is lower pressure blood flow easy
sympathetic vasoconstriction- vessel wall constricts to push blood toward heart
venous valves- appendages like arms and legs have many of these, they prevent blood from flow backwards.
regulating blood pressure
maintenance of BP involves regulating cardiac output CO, peripheral resistance (R), and blood volume. increase CO, R blood volume increases blood pressure. CO up body changes resistance so BP decreases and stays normal level.
CO factors affected- SV and HR
