Nails（1）

Nails（1）

Both humans and primates have nails. Some species of the simian suborder have no nails, and some species only have nails on part of their fingers. For example, the second toe of a monkey is a claw, and the rest are nails. However, only the first finger of the finger monkey has nails, and the other finger ends are claws. The main components of rhino horn and nails are keratin.

The nail is one of the accessories of the skin. Has its specific function. First of all, it has a "shield" function, which can protect the distal fingertips from damage, maintain their stability, enhance the sensitivity of the fingers, and assist in grasping, pinching, pinching, squeezing, etc. The nail bed is rich in blood supply and has the function of regulating peripheral blood supply and body temperature. Secondly, nails are the focus of hand beauty. Beautiful nails add female charm.

Nails are derived from the skin. Like the skin, it is formed by the mesenchyme of the embryonic body surface ectoderm and lateral lamina and its somatodermal sections gradually differentiated after 9 weeks of embryo. Nails are divided into nail plate, nail bed, nail fold, nail groove, nail root, nail epithelium, and hypothelium. The nail plate is equivalent to the skin with a layer, and the nailfold is the part of the skin that is bent into the nail groove. The nail bed is composed of the auxiliary layer equivalent to the epidermis, the basal layer and the dermal reticular layer. It is directly fused with the phalangeal periosteum. The posterior nailfold covers the nail root and migrates to the nail epithelium. In front of the nail bed is the hypodermis. Nail bed nail folds do not participate in the growth of the nail plate. Nail growth is formed by the proliferation, keratinization and migration of methyl cells at the root of the nail. But the nail bed controls the nails to grow in a certain shape. A damaged nail bed results in abnormal nail growth. The nail bed and nail root are rich in blood vessels. These provide rich nutrition for nail regeneration.