Quick Facts
A papilla is a small nipple-shaped projection, elevation, or structure. Here, they correspond to the spaces among the downward- or inward-projecting rete ridges on the under-surface of the epidermis (Dorland, 2011).
Structure/Morphology
The dermis has many upward projections that extend into the epidermis, known as dermal papillae. Likewise, the epidermis has alternated downward projections between the dermal papillae called the epidermal ridges.
Above the papillae of the dermis lies the dermoepidermal junction. This is an acellular zone between the dermis and the epidermis. The adhesion of the epidermis to the dermis is maintained at this junction by the interaction of hemidesmosome junctions and keratin filaments of the epidermis, and collagen and anchoring fibrils of the dermis (Baroni et al., 2012).
Function
This organization of epidermal ridges and dermal papillae at the dermoepidermal border increases the surface area of contact between the dermis and epidermis, thus strengthening the connection between the two layers.
References
Baroni, A., Buommino, E., De Gregorio, V., Ruocco, E., Ruocco, V. and Wolf, R. (2012) 'Structure and function of the epidermis related to barrier properties', Clin Dermatol, 30(3), pp. 257-62.
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
