Physiology of Finfish and Shellfish (2+1)

3.2.6. The myocardial cells

The sheets or bands of muscle fibres of the ventrides are arranged in a complex pattern. Some encircle only the cavity of the left ventricle. Others surround both ventricles in a helical pattern. This arrangement is advantageous because, when the ventricular muscle contracts the blood is virtually wrong, rather then pushed out of heart. The other aspects like fine structures of myocardial cells are similar to those of skeletal muscle cells. Cardiac muscle does not as extendis a reticulm as does the skeletal muscle. Cardiac muscle seens to depend on the influx of Ca²⁺ ions from either the extra cellular space or some other area during contraction, to supplement the Ca²⁺ ions released from the sacoplasmic reticulum.