The Pilosebaceous Unit: Week 14

Early hair peg

The hair pegs grow downward obliquely. Dermal papilla cells increase in number. A basal lamina separates the epidermal cells from the one or two layers of mesenchymal cells which surround the early hair peg. The follicular downgrowth is a solid mass of cells at this point in development, not the tubular structure characteristic of the mature skin. Cells from both the basal and first intermediate layers of the epidermis contribute to the hair peg. Two types of cells are present in the early hair peg; radially arranged peripheral cells are derived from the basal epidermal layer and rounded or longitudinally arranged interior cells are derived from the intermediate cell layer. Melanocytes are scattered throughout the hair peg and are functional.