Cardiac Muscle – Tutorial

Please read Unit 4 – Introduction to Muscle Tissue prior to completing the activities in this chapter.

Introduction to Cardiac Muscle

Cardiac muscle cells are found only in the myocardium of the heart.  Repetitive rhythmic involuntary (autonomic) contractions of cardiac muscle cells are what cause the heart to pump blood through the cardiovascular system.  Most cardiac muscle cells are cylindrical in shape and are shorter and smaller in diameter compared to skeletal muscle cells.  Cardiac muscle cells typically have a single, centrally located nucleus, however, some cardiac muscle cells can have two or three nuclei.  Cardiac muscle cells also exhibit striations, although the striations usually aren’t as distinct as those found in skeletal muscle cells when viewed under a microscope.  Although most cardiac muscle cells are cylindrical in shape, bifurcated (branched) cardiac muscle cells are quite common.  This gives cardiac muscle tissue the appearance of a branching network of interconnected cells when viewed in longitudinal section under a microscope.

Cardiac muscle cells are connected end-to-end by special intercellular connections known as intercalated discs.  Intercalated discs use desmosomes to connect cardiac muscle cells mechanically and gap junctions that allow ion movement between cells to connect cardiac muscle cells electrically.  The branched network of cardiac muscle cells along with the presence of intercalated discs between cells is what allows a single pacemaker region (SA node) of the heart to initiate action potentials that spread throughout the entire heart creating rhythmic contractions that move blood forward through the vascular system.

Tutorial:  Use the image slider below to learn more about the characteristics of cardiac muscle tissue. 

Microscopy:  Use the image slider below to learn how to use a microscope to study cardiac muscle tissue on a microscope slide.

Tutorial:  Use the hotspot image below to learn more about the characteristics of cardiac muscle tissue. 

Tutorial:  Use the image slider below to study numerous examples of cardiac muscle tissue.