1060- Structure and function of blood vessels Flashcards
What are the three outermost layers of blood vessels called ?
Tunica adventitia, tunica media and tunica intima
tunica intima
endothelial cells line the inner surface and the basal lamina
tunica intima in larger vessels
a subendothelial layer of loose connective tissue and an internal elastic lamina beneath the subendothelial layer.
tunica media
concentric layers of helically arranged smooth muscle cells with variable amounts of elastin and proteoglycans
tunica adventitia
longitudinally oriented collagen and elastin fibres
systole
expansion of the elastic arteries which limits the increase in pressure.
diastole
elastic recoil keeps the atrial pressure therefore maintaining the flow and preventing muscle collapse.
vasa vasorum
a network of small blood vessels which supply the walls of larger blood vessels
describe 2 structures of arterioles and two important functions
1-5 layers of smooth muscle cells . has a very thin adventitia . they constrict or relax to maintain mean arterial blood flow and to alter blood flow through capillaries down stream.
formula for the control of cardiac output
heart rate x stroke volume
MABP definition
the average pressure in systemic circulation
Darcy’s Law
pressure = flow x resistance
MABP formula
cardiac output x total peripheral resistance
why is regulating MABP a bit of a balancing act
must be maintained within normal limits so not to high otherwise there is the risk of tissue damage , or not too low as it risks the vessels collapsing. However due to metabolic demand regional changes in blood flow are demanded.
how does altering arteriolar radius alters TPR and hence MABP
because decreasing the vessel radius can cause relatively large increases in the vessel resistance .
name 3 vasoconstrictor stimulators
noradrenaline, angiotensin II and endothelin
name 3 vasodialator stimuli
adrenaline , acetylcholine and histamine
what kind of receptors do noradrenaline primarily act on ?
alpha- adrenergic receptors.
How does the medulla respond to increased MABP
decreases sympathetic and increases parasympathetic , which results in lower peripheral resistance and cardiac output. , which lowers MABP back to normal
How does the medulla respond to the reduced MABP ?
by increasing sympathetic and decreasing parasympathetic to raise TRP and CO therefore raising the MABP back to normal
What are capillaries surrounded by?
Pericytes
Why is blood flow velocity important?
Slowing of blood flow maximizes time available for exchange of substances between blood and interstitial fluid
What types of capillary are there ?
Continuous ,discontinuous and fenestrated
Continuous capillary structure and where is it found (5) ?
Tight junctions and continuous basal lamina
Found in brain, muscle, thymus, bone and lung
Discontinuous
capillary structure and where is it found ?
Large gaps between endothelial cells and discontinuous basal lamina
Found in tissues where there is a need for a close association of blood and surrounding cells (e.g. liver and spleen)
Fenestrated capillary structure and where is it found (3) ?
have many fenestrations and a continuous basal lamina , found in intestinal villi , renal and glomerular capillary tissues
