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The coronary
arteries are the first branches of the aorta and usually, arise within
the aortic sinuses of Valsalva.
There are two arteries, right and left,
but three sinuses. This permits the normal sinuses to be distinguished
as right coronary, left coronary and non-coronary.
The right
coronary artery emerges from the sinus directly into the antero-superior
part of the right arterioventricular groove. It then encircles the
tricuspid valvar orifice, giving rise to ventricular and atrial
branches. In nine-tenths of individuals, it gives rise to the
posterior interventricular artery and in most continues beyond the
crux to supply part of the diaphragmatic surface of the left ventricle
(right coronary dominance).
The left coronary
artery emerges from its sinus into the space between the pulmonary
trunk and the left atrial appendage. After a short course, usually of
no more than one centimeter, the left coronary artery divides into
anterior interventricular (descending) and circumflex branches. The
anterior artery runs down the interventricular groove, giving
perforating branches to the septum, infundibular branches to the right
ventricle, and diagonal branches to the left ventricle.
The circumflex
artery runs round the mitral orifice, usually with a short course and
gives obtuse ventricular and atrial branches. Sometimes the
first obtuse branch arises as a third artery directly from the left
main stem.
In one-tenth of
individuals, it is the circumflex artery which gives rise to the
posterior interventricular artery (left coronary dominance).
The areas of
heart supplied by the three coronary arteries are as follows:
1. Left anterior descending branch :
supplies anterior wall of left ventricle and adjacent area
of anterior right ventricle and anterior two-thirds of the interventricular septum (accept the apical region).
2. Left circumflex branch :
supplies lateral wall of the left ventricle.
3. Right coronary artery :
supplies remainder of the
right ventricle, posterior region of left ventricle and posterior
third of the interventricular septum.
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AUTOPSY EXAMINATION OF CORONARY ARTERIES:
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