Turn now to slide 66. This is the heart of yet another unfortunate rodent, but it has been sectioned transversely, below the level of the atrioventricular junctions. You should be able to make out most of the features identified in the previous slide, except those which are out of the plane of the section. To view some images of the heart, click here. Myocardium Look at slides 616 and 66 at low power, and observe the pattern of the muscle cells of the myocardium .
Myocardium constitutes the bulk of the heart's mass.
The shape of the myocyte is pretty irregular, with stumpy projections coming off of it where it contacts other cells. The histological appearance of myocardium is therefore completely different from that of skeletal muscle. The contacts between myocytes are such that a branching network with blood vessels in the spaces between them is the result. To see examples of typical myocytes, click here . Myocytes differ from skeletal myofibers in that cardiac myocytes are mononuclear and not syncytial.