STRIATED (CARDIAC) MUSCLE
In these views, first focus on muscle that is cut in longitudinal section and look for striations. Also, look for lines running perpendicular to the muscle fibers. These are intercalated disks and represent specialized junctions that allow for communication between the individual fibers (cells). Find an electron micrograph of an intercalated disk and identify the types of junctions and their functions.
Also note that the nuclei are larger than those in skeletal muscle and they are centrally located. In fact, the fibers may branch around a nucleus. Each cell (fiber) has only one nucleus.
What are the features that distinguish cardiac muscle from skeletal muscle?
Purkinje fibers are specialized for conduction. They have
scattered sarcomeres (contractile units) and large patches of glycogen. In the following photo, the glycogen has been dissolved in the processing of the section and shows only a
clear space. The cells are rounder than the normal cardiac muscle fibers.
Gwen V. Childs, Ph.D., FAAA
Department of Neurobiology and Developmental Sciences
University of Arkansas for Medical Sciences
4301 W. Markham, Slot 510
Little Rock, AR 72205