Cardiac Histology (X): Cellular population of the heart other than myocytes.

Cellular population of the heart, other than myocytes. A. Mast cells (arrows) can be seen in the myocardial interstitium of normal hearts (H&E 400X). B. Dendritic cells are part of the monocyte-macrophage system. They are found in the normal heart in pericapillary location. They cannot be discerned in H&E stains. Detection requires immunohistochemical staining. They become very prominent in miscellaneous inflammatory conditions and they play an important role in the initiation of immune responses because of their function in antigen presentation processing (Immunohistochemical staining with LN3 antibody. 300X). C. The innervation of the heart is abundant. The epicardial surface contains abundant nerves and nerve endings. This micrograph shows a cluster of ganglion cells in the atrial epicardium (H&E 400X). D. Nerve bundles are also easily found in routine histologic sections, mostly near vascular structures. This micrograph shows a minute plexus around an epicardial coronary vessel (Movat pentachrome 25X). E and F. In the newborn, the cephalad portion of the atrial septum contains abundant adipose tissue and brown fat, along with ganglion cells and small nerves. This area, located near the great vessels, is heavily populated by neural crest derivatives. These micrographs show the various cell types populating this area of the heart. Note the well defined collagen network forming the boundaries between the two atrial walls (H&E and Movat pentachrome 20X).

Besides these additional cell types, other histological components of the heart include the cells of the endocardium and specialized atrial cells