The hair: Classification

Classification

Hairs are classified into three main types.

1  Lanugo hairs. Fine long hairs covering the fetus,but shed about 1 month before birth.

2 Vellus hairs. Fine short unmedullated hairs cover-ing much of the body surface. They replace the lanugo hairs just before birth.

3  Terminal hairs. Long coarse medullated hairs seen, for example, in the scalp or pubic regions. Their growth is often influenced by circulating androgen levels. Terminal hairs convert to vellus hairs in male pattern alopecia, and vellus to terminal hairs in hirsutism.

The lips, glans penis, labia minora, palms and soles remain free of hair follicles.