Blood vessels Flashcards
list the features and properties of arteries
-smooth muscle - contractile power and regulates diameter of lumen.
-adventitia - structural support, tethers vessels in place.
- elastin- expand and recoil
- endothelium- filtering interface between blood and body
list the features of arterioles
smooth muscle cells
lumen
endothelium
pre-capillary sphinchter- controls blood flow to specific capillary beds
what is active hyperaemia?
the increase in blood flow according to the metabolic needs of the tissue
eg. a increase in metabolic activity leads to arteriolar dilation which increases blood flow
what is flow autoregulation?
maintenance of blood flow rather than changing it.
eg. when the driving pressure drops the vessels dilate to restore normal value and when it increases the vessels constrict.
what happens to the vessels when arterial pressure increases ?
blood vessels constrict
when MAP decreases vessels dilate
with increasing sympathetic stimulation do vessels dilate or constrict?
vasoconstrict as norepinephrine is released
which receptors does circulating epinephrine bind to to cause vasodilation?
beta receptors causes vasodilation of skeletal muscle arteries
list the vessels in order
artery-arteriole-capillary-venule -vein
what is fick’s law of diffusion?
flow of gas= area/thickness x D x (P2-P1)
if hydrostatic pressure increases does this force fluid in or out of capillaries?
out of capillaries
if colloid osmotic pressure of proteins within capillaries decreases do this pull fluid into or out of the capillary?
into the capillary
what must occur for filtration to occur from the capillaries to the interstitial fluid?
hydrostatic pressure > osmotic pressure
what must occur for absorption of fluid from the interstitial fluid into the capillaries?
colloid osmotic pressure > hydrostatic pressure
how are veins different to arteries?
larger volume capacity
lie closer to the skin surface
larger diameter
have valves
less elastic tissue
less smooth muscle
more distensible (swell)
thinner walls
whats the difference in pressure between the veins and arteries?
veins have a pressure of 10mmHg whereas arteries have a pressure of 100 mmHg
are veins affected by hydrostatic pressure?
yes HP opposes blood flowing towards the heart
what is the frank-starling mechanism?
SV increases with increasing venous return
how is pressure in veins?
low and non-pulsatile
how can compliance of a vein be changed?
neural - sympathetic stimulation releases norepinephrine to veins of smooth muscle causing vasoconstriction reducing vol of blood to those organs
hormonal- diameter of veins affected by circulating epinephrine
how does the skeletal muscle pump send blood towards the heart?
compression of veins by muscle contraction empties veins of blood towards the heart
what happens to the diaphragm during inspiration?
diaphragm contracts moving downwards, increasing the volume of the thoracic cavity and decreasing the volume of the abdominal cavity
what happens to blood flow to the heart during inspiration?
flow increases due to the fall in intrathoracic pressure (chest expansion) and the rise in intraabdominal pressure (abdominal compression)
what happens to blood flow to heart during expiration?
flow is impeded due to rise in intrathoracic pressure (diaphragm relaxes)
what does the respiratory pump create in order to promote blood return to the heart?
a pressure difference between the abdomen and the thoracic cavity
