Physiology 9 Special circulation
Looking at specialised circulation systems
Coronary circulation
right
and left coronary arteries
Blood demand resting 70-80ml\min\100gs heavy exercise 300-400
the contraction of the heart leads to flucutations in the coronary supply
The heart extracts 75% of oxygen from blood
regulation of coronary blood flow
Major stimulus is O2 depletion even a drop like 5% can cause coronary vasodilation however local metabolic control is most important
increase of blood flow to the heart is largelyrgeulated by metabolic calibration Adenosine is likely released from the myocardiocytes to induce vasodiltion
NO is also produced to trigger VD
issues
functional end arteries no cross overs (arterioaterial anastemoses) so of one is block there is no 2nd path
Cerebral circulation
brain has no capacity for anaerobic metabolism
the internal carotid arteries mainly supply rhe anterior cerebral circulation
vertebral arteries supply the hindbrain under normal circumstances there is little mixing of the blood
if one is occluded circle of willis takes over and provides collateral flow
changes
Myogenic mechanisms mainly change the blood flow, through smooth muscle contraction
metabolic changes also give the brain oxygen when its needed where its needed
acidity is not well tolerated so blood flow is immediately increased
the brain blood and csf must remain with a constant value
cutaneous circulation
capillary loops to bring large amounts of blood to the skin
after a long time vasoconstrictor is overcome but not in reynauds disease
Splancic circulation
all intestinal bloode goes tho the liver especially in the fed state
sympathetic nervous system is a main regualtor in the splanchnic blood flow
in haemorrhage tip of villus may not be perfused severe hypoperfusion can lead to intestinal lineing breakdown leading to endotoxins getting in and septic shock
Hepatic
discontinuous and fenestrated capillaries portal vein supply is decided by the gut
hepatic artery bring oxygenate blood
hepatic artery + portal vein = inflow these can be
Kidneys
cue nephron structure
high bp can assist filtration
macula densa cells can detect sodium serum changes
this changes glomerular filtration