HA2: Papillary muscle
At either end of a nucleus, there is a conical region without striations that contains granules. These are very large and numerous cardiac mitochondria (arrows, HA2). Cardiac muscle is highly vascular, so there are many capillaries (5-7 in HA2). Because of the intercalated disks and the dense vascularity, the myofibers branch (HA2L).