Types of cell contacts in different smooth muscles
It is generally agreed that, where present, gap junctions or nexuses provide low-resistance pathways for cell-to-cell coupling of activity. Though these contacts were first described in smooth muscle and occur widely there, some types of smooth muscle contain few or no gap junctions, and many contain other types of contacts.A variety of smooth muscles from several species was fixed with phosphate-buffered glutaraldehyde by intra-arterial perfusion or by immersion of small strips. Samples were prepared for electron microscopy by standard methods, using oriented embedding to view muscle in both longitudinal and cross sections.Four types of cell contacts were identified in various smooth muscles, which have been previously recognized. 1) The gap junction or nexus appears with the usual double staining as a five-layered contact, often with adjacent clear areas of cytoplasm (Fig. 1).