Cardiovascular System - POSSIBLE QUESTIONS
Discuss
about intrinsic and extrinsic mechanisms involved in control of blood flow.
The intrinsic mechanism was described here. The extrinsic mechanism is described in your lecture series here.
The
heart receives a rich blood supply because of its intense activity throughout
life. The blood supply to the heart is termed the coronary circulation. The two
main arteries, right and left coronary arteries arise from the aorta.
The
left coronary artery splits into two branches. The anterior interventricular
branch and the circumflex branch. The former supplies the myocardium of both
ventricles and the interventricular septum. The latter only supplies the left
ventricle and the left atrium.
The
right coronary artery branches into two arteries namely: the posterior
interventricular branch and the marginal branch. The former supplies the right
ventricle and the interventricular septum and the latter supplies the right
ventricle and right atrium.
Thus
each artery supplies both ventricles and the septum, and has an additional
branch supplying its own side. Because the heart contracts in a pulsatile
nature, the blood supply to the myocardium is blocked during systole, but when
the muscle relaxation blood begins to flow again.
The
blood flows through the heart and then drains into two venous branches. The
great cardiac vein drains the anterior heart and the middle cardiac vein drains
the posterior part. These then eventually drain into the cardiac sinus, which
drains into the right atrium to begin the circulation once more.
Major
Points: Left and right coronary branches come from aorta