CH 9 Cardiac Muscle Histology J.F. Thompson, Ph.D.

The Myocardium Forms most of the heart wall (myocardium)

Cardiac Muscle Individual uninucleate cells (may occasionally be binucleate) –Not dividing Rich capillary blood supply

Cardiac Muscle Striated Cells may be branched

Cardiac Muscle Involuntary (unconscious) Autorhythmicity (contracts without external stimuli) Rapid contracting and relaxing Non-fatigable

Cardiac Muscle Cells Each fiber is connected to the others by intercalated discs

Intercalated Discs Tight Junctions Desmosomes –connect cells Gap junctions –Electrical synapses –Excitation spreads rapidly

Cardiac Muscle Note the striations which represent myofibrils and the sliding filament method of muscle contraction.

End CH 9 Cardiac Muscle Histology