Figure 2­51
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As you will recall, skeletal muscle consists of multinucleated cells. Coordinated contraction of these cells produces
movements of the body or its parts. On the other hand, smooth muscle consists of individual, singly nucleated cells
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with little intercellular space. Yet these cells can contract in a coordinated manner. The presence of communicating
junctions between the smooth myocytes allows them to function as a physiologic syncytium. The plasma membranes
Holdings,
of adjacent cells are closely opposed, with very little extracellular matrix between them. Modifications of the cell
surface, which are called connexons, are gated channels that permit the passage of small ions from one cell to the
next, resulting in contraction of the cells in concert with other cells. Communicating junctions are also located in
LLC.
cardiac muscle and in epithelial cells; they are absent from skeletal muscle.
Not
Two areas of communicating junctions are depicted in the left and center of the field (arrows).
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