Module 7: Figure ventricle cell
Structural organization of the cardiac ventricular cell.
The plasma membrane has periodic transverse tubules (T-tubules), which extend deep into the cell at regular intervals that coincide with the Z-band of the contractile myofibrils. The bulk of the cell is composed of these striated myofibrils, which are surrounded by mitochondria and by the sarcoplasmic reticulum (SR). The SR has two parts: the longitudinal SR that forms a meshwork around the myofibrils and the junctional SR that make closes contact with the T-tubules to form the dyadic junction. It is at this dyadic junction where the electrical signal travelling down the T-tubule triggers the release of Ca2+ from the junctional SR during the process of excitation–contraction (E-C) coupling. Reproduced from William Bloom and Don W. Fawcett, A Textbook of Histology, 10th edition (W.B. Saunders, 1975), © 1975 by W.B. Saunders Company, reproduced by permission of Edward Arnold (D.W. Fawcett and S. McNutt, Journal of Cell Biology, 42:1, 1969); see Bloom and Fawcett 1975.