Electron microscopic observations of human hair medulla.

In the study of human hair, medulla is the less studied structure because it is believed that it has no influence on the fibre properties. The aim of this paper is to contribute to the better understanding of medulla morphology. Using reproducible methods for hair samples preparations allowed observing the inner fibre by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Three medulla subunits were observed in cryofractured samples. In addition, the application of plasma etching on samples allowed accessing chemical differences between them. Two kinds of medulla were identified using stereomicroscopy: thin and thick medulla. They were morphologically differentiated using TEM. These methods can be used to study systematically the effects of medulla on hair properties and to evaluate the efficiency of cosmetic products.