Only cardiac muscle has this particular appearance, which is given to it by something called intercalated discs. Cardiac muscle also consists of single muscle cells, called Cardiomyocytes; where something such as skeletal muscle cells are MULTInucleated (more than one cell nucleus).
mitochondria packed between myofibrils in cardiac muscle the crystalline appearance of the numerous mitochondria is a result of densely packed cristae or infoldings of the inner membrane this design dramatically increases the surface area of the inner mitochondrial membrane in which ATP-producing machinery is embedded colored TEM credit: Science Photo Library
No bones about it; your bones can’t do much without muscles to move them. You have three major types of muscle tissue known as skeletal, smooth, and cardiac muscle. Learn about all 11 organ systems with the Amoeba Sisters! http://www.youtube.com/watch?v=nnjmrrQ6xOs
Heart muscle cells (shown in green), regress to a more youthful state after injury, start dividing again (indicated by a red marker) to replenish lost cells and then mature a second time into cardiomyocytes.