The Pilosebaceous Unit: Week 12

Condensations of mesenchyme

Condensations of mesenchymal cells occur at regular intervals just below the dermal-epidermal junction. These cells are destined to become the dermal papilla. In development, the dermal papilla is important for induction of pilosebaceous unit formation. In mature skin, the dermal papilla has a critical role in controlling the hair cycle. After the dermal mesenchymal cells begin to aggregate, the epidermal keratinocytes immediately above the condensate cluster and bulge downward into the dermis. Melanocytes are already present among the clustering keratinocytes.

Thin section LM