Page 48 - Clinical Anatomy

ECA1 7/18/06 6:31 PM Page 33

The mediastinum 33

Fig. 26◊The interior of the left ventricle.

throughout the atrial musculature to reach the atrioventricular node lying in
the atrial septum immediately above the opening of the coronary sinus. The
impulse is then conducted to the ventricles by way of the specialized tissue
of the atrioventricular bundle (of His). This bundle divides at the junction of
the membranous and muscular parts of the interventricular septum into its
right and left branches which run immediately beneath the endocardium to
activate all parts of the ventricular musculature.

The blood supply to the heart (Fig. 27)
The heart’s blood supply is derived from the right and left coronary arteries
whose main branches lie in the interventricular and atrioventricular
grooves.
The right coronary artery arises from the anterior aortic sinus and passes
forwards between the pulmonary trunk and the right atrium to descend in
the right part of the atrioventricular groove. At the inferior border of the
heart it continues along the atrioventricular groove to anastomose with the
left coronary at the posterior interventricular groove. It gives off a marginal
branch along the lower border of the heart and the posterior interventricular
branch which runs forward in the inferior interventricular groove and to
anastomose near the apex of the heart with the corresponding branch of the
left coronary artery.