Plasma membrane differentiations of keratinizing cells of the wool follicle: III. Tight junctions

Abstract

Tight junctions in the keratinizing regions of the wool follicle have been studied primarily by the freeze-etch method. The evidence obtained indicates that tight junction zonulae are present in the plasma membranes of apposed Henle's cells, Henle's/Huxley's cells, and Henle's/companion cells. These zonulae were found from a region level with the middle of the dermal papilla up to where the inner root sheath is finally entirely hardened. From this, it is hypothesized that a function of Henle's layer is to seal off the extracellular space of the outer root sheath from that of the differentiating inner root sheath—fiber complex. The presence of both desmosomes and gap junctions within the tight junction zonulae was noted.