Cardiac muscle



Cardiac muscle explanatory video


Cardiac muscle fibers are elongated as in skeletal muscles and they contain myofibrils which exhibit both longitudinal and transverse striations as in skeletal muscles. It is does not regenerate and maintain a constant rhythmic contraction.

Cardiac muscle is striated but not syncytial.   Its muscle cell is short and it consist of one or more rounded nuclei.   It also has similar organelles with striated muscle in its sarcoplasm and that include numerous mitochondria. Its myofibrils are not many as in other myocytes. Cardiac myocyte is similar to red skeletal muscle rather than white one and just like red meat, it also has large amounts of myoglobin and glycogen.The myofibrils have actin and myosin myofilaments components which are disposed in a similar fashion as in the striated muscle.   They have A bands which are dark portions consisting of actin and myosin.   They have I bands, consisting of only actin.   They have the Hensen line on the A band and also the Z disc which delimits the extents of the sarcomere.

The major difference between the striation of the cardiac and skeletal muscles is the availability of the so called intercalated discs in the cardiac muscle, which are specialized modifications of the two discs occurring at junctions between cells.

      Intercalated discs have a special significance in the sense that they are non existent in the new born but become numerous in the adult,  increasing with age.   They are not found at every Z discs, but they exhibit a ladder like architecture which makes them so unique.When isolated, cardiac myocytes contain spontaneously in a rhythmic fashion. They ae supplie by autonmic fibers from sympatehtic and parasympatheti system







   Smooth muscle

   Striated muscle

   Cardiac muscle

Gross anatomy
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Smooth muscle      

Striated muscle      

Cardiac muscle      


Smooth muscle      

Striated muscle    

Cardiac muscle      

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  Electronic School of Medicine
Creator: Oluwole Ogunranti


Cardiac muscle microscope          Double click for full screen


Intercalated disc







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