What is a dermal papilla?

Answer 1

In the human skin, the dermal papillae (DP) (singular papilla, diminutive of Latin papula, 'pimple') are small, nipple-like extensions (or interdigitations) of the dermis into the epidermis. They can be observed at the surface of the skin in hands and feet as [[Epidermal ridge|epidermal]] or [[Papillary ridge|papillary ridges]] (colloquially known as fingerprints. The dermal papillae nourishes all hair follicles and bring food and oxygen to the lower layers of epidermal cells. The pattern of ridges they produce in hands and feet are inherited features that are developed before birth. They remain unaltered (except size) throughout life, and are therefore used for fingerprints. The dermal papillae are part of the uppermost layer of the dermis, the papillary dermis, and the ridges they form greatly increase the surface area between the dermis and epidermis. Because the dermis' main function is to support the epidermis, this greatly increases the exchange of oxygen, nutrients, and waste products between these two layers. Additionally, the increase in surface area prevent the dermal and epidermal layers from separating from each others by strengthening the junction between them. With age, the papillae tend to flatten and sometimes increase in numbers. Dermal papillae also play a pivotal role in hair formation, growth and, cycling.