Trichohyaline granules in hair cortex.

A granular structure was found in the keratogenous zone of the cortex in human hair follicles. This granule was a round, relatively electron-dense, homogeneous structure 0.1-0.3 micron in diameter and not membrane-limited. It appeared in cortical cells in the keratogenous zone, fused to the tonofilaments, and disappeared before the complete keratinization of the cortex. Thus, this granule was considered to be a trichohyaline granule. Similar granules were found in the nuclei of cortical cells in the keratogenous zone. A comprehensive survey of various human hairs confirmed this observation. Trichohyaline granules were also present in the cortical cells of guinea pig hair in the keratogenous zone. However, a similar survey on mouse hair cortex did not reveal trichohyaline granules in this species.