Main Page | See live article | Alphabetical index A gap junction is a junction between certain animal/plant cell-types that allows different molecules and ions to pass freely between cells. The junction connects the cytoplasm of cells together and also functions to physically hold the cells together. Gap junctions are particularly important in the cardiac muscle: the signal to contract is passed efficiently through the gap junctions, allowing the heart muscle cells to contract in tandem. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.