- coronary circulation
Major vessels of coronary comprises
*Left coronary artery left anterior descending
*22-250 ml/min blood flow
-Factors
pressure in aorta
chemical factor
neural factor
autoregulation
* cutaneous circulation
. Supply the skin metabolically active tissue.
small energy required
there is an anastomosis between a small artery and veins that share a role in temperature regulation low resistance connection between them.
*triple response flush capillary dilation
-Flare arteriolar dilation
-Wheal edema
*Cerebral circulation
Its movement of blood through a network of cerebral artery and veins supplying brains important for the healthy functioning of the brain.
able to change blood flow by acting by diameter autoregulation.
they constricted when systemic BP is raised and delighted when it is lowered
-arterioles also constrict and dilation in response to drift in chemicals.
regional circulation
flow of blood in the region which are clinically important, concerning their Rapid Anatomical arrangements, function variations, factors regulating,.
-coronary circulation:- right and left coronary arteries supplies heart.
arise from sinus at the root of aorta
right coronary artery supplies right ventricle and posterior part left ventricle..
left coronary artery supplies anterior and Lateral portion of left ventricle .normal coronary blood flow 225 to 250 ml per minute 5 percentage of cardiac output capillary density is high in coronary arteries.
coronary arteries are end arteries.
factors
- phases of the cardiac cycle
blood vessels supply myocardium, endocardium passes through layers of heart perpendicular to the main artery. therefore blood vessels are compressed at systole
During diastole, a major part of the blood supply occurs, cardiac muscles relax and blood vessels are no longer compressed, hence blood flows through capillaries.
chemical factors:-
metabolic activity research in the accumulation of end products such as lactates and hydrogen ions. during anaerobic metabolism, there is formation of adenosine from ATP and prostaglandin in the cardiac tissue
-the substances increases blood flow due to local vasodilation .cardiac muscle extracts 70% of oxygen from the coronary arterial blood
-factors influencing vasodilation.:-
oxygen lack, CO2 excess increase in potassium ions concentration adenine accumulation intracoronary injection of Cyanide
-coronary artery occlusion increases blood flow due to the release of adenosine term as reactive hyperemia
-Autoregulation
The ability of visceral organs heart-brain kidney regulate its blood flow with a narrow range of fluctuation this operates between arterial BP of 60 to 160 mm Hg
- neural factors:- stimulation of sympathetic nerves to the heart increases heart rate, produces initial vasoconstriction. the accumulation of metabolic end-products and adenosine finally produces vasodilation by its local action.
- cerebral circulation-
- in humans to internal carotid and two vertebral arteries supply the brain normal cerebral blood flow= 750 ml per minute for 54 ml per 100 gram of the tissue
-factors.
Autoregulation. The brain maintains its blood flow despite variation in arterial blood pressure.
-Hypoxia.
-hypoxia to the Brain increases blood flow by vasodilation.
-oxygen excess
High oxygen concentration produce vasoconstriction reduces blood flow to the Brain to prevent its damage
-hypercapnia. Increased levels of CO2 concentration in blood cause vasodilation due to local effect enhancing blood flow.
-Intracranial pressure. Increases in the pressure decrease cerebral blood flow.
- Perfusion pressure.
Pressure difference between arterial and venous system of the brain.
* Cutaneous circulation
- circulation through skin.
Blood flow 400 to 450 ml per minute .plays an important role in the regulation of body temperature it acts as a reservoir of blood. blood flow to the skin is highly variable.
-Factors.
Sympathetic stimulation decreases blood flow.
-Increased body temperature cause vasodilation, decrease blood flow.
Epinephrine and norepinephrine cause vasoconstriction. decreased blood flow
Bradykinin and histamine cause vasodilation .increased blood flow
* white reaction:-
when the skin is stroked lightly the skin appears pale due to reduced blood flow.
this response is due to constriction of precapillary sphincter called white reaction.
triple response -when the skin is stroked /scratched it shows three reactions.
1)red reaction:-appearance of the red line where the stroke is made.
due to relaxation of precapillary, influenced by histamine
appearance in 10 seconds well developed in 1 minute.,
2)flare:-when stroking is firm an area of redness developed surrounding site, due to arteriolar dilation as a result of axon reflex, the area has increased temp.
3)wheal:-in the stage fluid collects around the stroked area, resulting in edema.
fluid is transudate, produced due to increased hydrostatic pressure in the dialed capillaries
-triple response is largely due to the local release of histamines.
3)wheal:-in the stage fluid collects around the stroked area, resulting in edema.
fluid is transudate, produced due to increased hydrostatic pressure in the dialed capillaries
-triple response is largely due to the local release of histamines.
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