Blood Vessels and Circulation Flashcards
5 classes of blood vessels
arteries
arterioles
capilleries
venules
veins
arteries
carry blood away from heart
high pressure
thicker tunica media than tunica externa
small lumen
arterioles
are smallest branches of arteries
little or no tunica
have thin or incomplete tunica media
regulate the distribution of flow of blood to capillary beds
capillaries
small blood vessels
location of exchange between blood and interstitial fluid
venules
collect blood from capillaries
veins
return blood to heart
lower pressure (works against gravity)
thinner: tunica externa thicker than tunica media
larger lumen
has valves
largest blood vessels
pulmonary trunk
aorta
smallest blood vessels
capillaries
tunica externa
outermost layer
elastin and collagen strengthens,
anchor contains nerves and tiny blood vessels
tunica media
middle layer
circular smooth
vaso-constriction/dilation
tunica intima
innermost layer
endothelium
minimize friction
lumen
interior opening of the vessel
capillary network
capillary bed or capillary plexus connect 1 arteriole and 1 venule
capillary sphincter
guards entrance to each capillary
opens and closes, causing capillary blood to flow in pulses
vasomotion
bloodflow in capillary beds constantly change routes
medium sized veins
thin tunica media and frew smooth muscle cells
tunica externa with longitudinal bundles of elastic fibers
large veins
have all 3 tunica layers
thick tunica externa
thin tunica media
vein valves
folds of tunica intima prevent blood from flowing backward
compression pushes blood toward heart
capillary bed:
at arterial end
fluid moves out of capillarie
into interstitial fluid
capillary bed:
at venous end
fluid moves into capillary
out of interstitial fliud
excess fluid in capillary bed goes in _________________
the lymphatic vessel
systolic pressure
peak arterial pressure during ventricular systole
diastolic pressure
minimum arterial pressure during diastole
pulse pressure
difference between systolic pressure and diastolic pressure
vasodilation
the relaxation of arterial smooth muscle enlarging the lumen
vasoconstriction
the contraction of arterial smooth muscle by ANS
smaller vessels contribute to ________
the most resistance
blood viscosity
determined by the ratio of RBC’s to plasma volume
venous retrurn
amount of blood arriving at right atrium each minute
low venous resistance
assisted by muscular compression of preipheral veins
the respiratory pump
compression of skeletal muscle pushes blood ___________ the heart
toward
if blood pressure is too low
vessels collapse and blood flow stops
tissue dies
if blood pressure is too high
vessels will stiffen
capillary bed may rupture
3 regulatory mechanisms
autoregulation
neural regulation of blood pressure
hormonal regulation of blood pressure
autoregulation
causes immediate homeostatic adjustment
physical changes
vaso dilation/constriction
neural regulation of blood pressure
ANS regulates blood pressure through baroreceptors reflexes and chemoreceptor reflexes
hormonal regulation of blood pressure
long term regulation of blood flow
3 effects of light exercise
extensive vasodilation
venous return increases
cardiac output rises
5 effects of heavy exrecise
activates sumpathetic nervous system
cardiac output increases to maximum
restricts blood flow
redirects blood flow to skeletal muscles, lungs and heart
blood supply to brain is unaffected
lactic acid and low levels of O2
dilate coronary vessels
increase coronary blood flow
epinephrine
dilates coronary vessels
increases heart rate
strengthens contractions
