gap junction

Definition:

1. an intercellular junction formerly considered to be a tight, membrane-to-membrane junction (macula occludens) but now shown to have a 2-nm gap between apposed cell membranes; the gap is not void but contains subunits in the form of polygonal lattices, which are the intercellular aspects of the two connexons that fit together, forming a channel between the cytoplasms of the two cells; it occurs in epithelia, between certain nerve cells, and in smooth and cardiac muscle; it is believed to mediate electrotonic coupling, which allows ionic currents to pass from one cell to another.
2. areas of increased electrochemical communication between myometrial cells that aid in the propagation of the contractions of labor.

Synonym(s): communicating junction, electrotonic junction, electrotonic synapse, macula communicans, nexus

See Also: synapse

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