Ultrastructure and function of the lamina propria of mammalian seminiferous tubules.

The lamina propria of the seminiferous tubules comprises the basement membrane, plus one or more layers of cells, depending on the species, and intercellular material. The myoid (contractile) cells are nearest to the seminiferous tubules. In larger mammals, several layers of contractile cells, surrounding the seminiferous tubules are normally present. They are charaterized by the presence of boundles of 80 A filaments, which are responsible for the contractility. It is supposed, that the myoid cells are renewed from adjacent peripheral fibroblast-like cells.