Abstract:
Coronary circulation
The two coronary arteries that supply the myocardium arise behind the aortic valve at the root of the aorta. Venous blood returns to the heart through the coronary sinus and anterior cardiac veins which drain into the right atrium Coronary blood vessels receive sympathetic and parasympathetic innervations. The predominant effect of sympathetic stimulation in coronary arteries is vasodilation.
Coronary artery diseases:
Coronary arteries bypass grafting:
The internal mammary arteries, radial arteries or segment of patient s own saphenous vein can be used to bypass coronary artery stenosis. This usually involves major surgery under cardiopulmonary bypass.
Splanchnic circulation
Skin circulation
- The skin has an anastomosis between arteries and veins especially in fingers, toes and earlobes.
- There is variation in BF between 1 – 150 ml/ 100 gm of skin /min.
- Skin is considered as blood reservoir.
- The cutanous vessels constricted in stimulation of:
1- noradrenergic nerve.
2- circulating norepinephrine,
3- exposure to cold and painful stimuli.
Microcirculation
The major mechanisms for exchange are
diffusion and filtration. Diffusion is much more important in exchange of nutrients and waste materials between blood and tissue. O2 and glucose are in higher concentration in bloodstream than in the interstitial fluid, so they diffuse to the interstitial fluid, whereas CO2 diffuses in the opposite direction. The rate of