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The dermal papillae (DP) (singular papilla, diminutive of Latin papula, 'pimple') are small, nipple-like extensions (or interdigitations) of the dermis into the epidermis. At the surface of the skin in hands and feet, they appear as epidermal, papillary or friction ridges (colloquially known as fingerprints ).
Epidermal thickenings called Rete ridges (or rete pegs) extend downward between dermal papillae. [7] Blood capillaries are found beneath the epidermis, and are linked to an arteriole and a venule. The epidermis itself has no blood supply and is nourished almost exclusively by diffused oxygen from the surrounding air. [8]
Rete pegs (also known as rete processes or rete ridges) are the epithelial extensions that project into the underlying connective tissue in both skin and mucous membranes. In the epithelium of the mouth, the attached gingiva exhibit rete pegs, while the sulcular [ 2 ] and junctional epithelia do not. [ 3 ]
H&E stained section of human skin. The dermoepidermal junction or dermal-epidermal junction (DEJ) is the interface between the epidermal and the dermal layers of the skin. The basal cells of the epidermis connect to the basement membrane by the anchoring filaments of hemidesmosomes; the cells of the papillary layer of the dermis are attached to the basement membrane by anchoring fibrils, which ...
Pig skin especially shares similar epidermal and dermal thickness ratios to human skin: pig and human skin share similar hair follicle and blood vessel patterns; biochemically the dermal collagen and elastin content is similar in pig and human skin; and pig skin and human skin have similar physical responses to various growth factors. [1] [2]
These epidermal ridges serve to amplify vibrations triggered, for example, when fingertips brush across an uneven surface, better transmitting the signals to sensory nerves involved in fine texture perception. [8] These ridges may also assist in gripping rough surfaces and may improve surface contact in wet conditions. [9]
The dermal papillae between the elongated rete ridges are frequently dome shaped. Necrotic keratinocytes can be observed in the basal layer of the epidermis and at the dermal-epidermal junction. Eosinophilic remnants of anucleate apoptotic basal cells may also be found in the dermis and are referred to as “colloid or civatte bodies”.
In a growing fetus, fingerprints form where the cells of the stratum basale meet the papillae of the underlying papillary layer of the dermis, resulting in the formation of the ridges on the fingers. Fingerprints are unique to each individual and are used for forensic analyses because the patterns do not change with the growth and aging processes.