Anatomy of nails

NOCTIES (UNGUES, ONYX)
 
Nails, as well as hair, fat and sweat glands, are skin appendages of epic origin.
The nails are in close anatomical relation to the phalanges, which in turn determine the shape and curve of the nail. The bone marrow is a fibrocargoscopic net in which there is no hypodermis and pilo-besser apparatus. It is located in a small area between two rigid structures - the nail plate and the phalanx. Compared to epidermal keratinocytes, nail-matrix keratinocytes are larger and have a high proliferative structure.
The nails are thicker and grow slower than the nails. Complete replacement of the nail plate occurs for 6 months - for nails up to 18 months - for nails.
 
Nail Structure
 
The ankles have five anatomical regions:
1) nail plate;
2) proximal nail fold;
3) nail matrix;
4) nail bed and
5) hyponium.
 
Proximal nail fold, nail matrix, nail bed, and hyponhythmia are specific epithelial formations.
 
Ankle plate
 
The nails are thick, horned tiles - lamina ungualis, located on the dorsal surface of the end phalanges of the fingers. They are transparent with a light pink color and a smooth, convex surface that may have Beau stretch marks. These transversal grooves increase with age and can be used for legal recognition.
The shape of the nail tiles is rectangular, their thickness is different and depends on age, gender, internal and external impacts. The front end of the nail plate is free - margo liber, while the margo occultus and margines lateralis are covered with a vallum unguis, forming a furrow - sulcus unguis.
The nail differs between corpus unguis and radix unguis. At the back of the nail plate is a white arc called lunula. The nail plate lies on the nail bed - lectulus unguis.
Anticoagulated tiles are composed of tightly attached keratinocytes (onychocytes). Much of the nail plate originates from the nail-matrix epithelium. Like corneocytes of the epidermis and trichocytes of the hair stem, onychocytes of the nail are composed of keratin fibers. Between 80 and 90% of the keratin fibers of the nail plate are solid. Other constituents of nail tiles are water, lipids, traces of iron, zinc, calcium, lipids from 0.1% to 5%. The water content in the nail plate is about 7-18%. A water content of less than 7% is the cause of nail fragility. A water content of over 30% causes clouding and softening of nails. The nail plate is 1000 times more permeable to water than the skin, and as a result of high porosity, the nail plate can be hydrated and dehydrated very easily.
The homogeneous pink color of the nail is due to the underlying capillaries. On some of the nails, especially the thumb, in the proximal part of the nail plate there is a semi-moon region - a lunula. In this area, the attachment of the nail plate is weaker, and in this area it is easier to penetrate microorganisms, as well as damage by physical factors.
The free edge of the nail plate has a thin, transversal whitish strip called onychorneal strip. It is a very important anatomical barrier for external influences. Its disturbance leads to distal onycholysis (peeling of the nail plate).
Even after death, nails continue to grow. This phenomenon is due to contraction and is similar to post-mortem growth of the beard. The slow growth of the nail plate makes it an archive of pathological processes that occurred months ago. Proximal nail fold
 
A large part of the nail plate is visible, only 1/3 of it covered by the proximal nail fold. The horn of this crease formed the eponymous. The dorsal part of the proximal nail fold continues in the skin of the back of the hand. The underlying dermis contains capillaries. These vessels are damaged in autoimmune diseases. The ventral portion of the proximal nail fold continues into the nail matrix and attaches to the nail plate.
Nodular matrix
The clamp matrix is ​​wedge-shaped. It is composed of a highly specialized epithelium and can be conventionally divided into a proximal and distal part.
In the nail matrix, Langerhans cells are found - mainly in the suprabasal layers of the proximal nail matrix and the Merkel cells. The number of Merkel cells is age-dependent and they are more numerous in the fetus than in adult individuals.
 
Ankle bed
 
The nail bed lies below the nail plate starting from the distal edge of the lunate and reaching the onychodermal joint. The strong connection between the nail bed and the nail plate is due to the corresponding longitudinal grooves. This bonding is so strong that when extracting the nail plate the epithelium of the nail bed remains on the lower surface. The nail bed determines the direction and length of the growth of the nail plate, and in part contributes to its shape.
Melanocytes are found in high density in the nail matrix and the presence of malanocytes in the nail bed is controversial. In contrast to epidermal melanocytes, which are located between the keratinocytes of the basal layer, the nail-matrix melanocytes are located mainly in the distal matrix and suprabasal. Melanocytes of the nail matrix of dark pigmented skin contain mature melanosomes and synthesize melanin, those of the light skin are usually latent and do not contain mature melanomas. Various physiological and pathological stimuli can activate nail-matrix melanocytes. In Asians and Africans there is a diffuse or striped pigmentation.
 
Blood supply and innervation of the nails
 
The ankle system has a rich blood supply, which is provided by the digital arteries lying to the phalanges - four arteries for each finger, two on each side. A unique anatomic feature is the large arterio-venous anastomoses at all sites in the nail unit, except for the proximal nail fold. These anastomoses can be simple unmodified anastomoses or a specialized body of vessels - gloss cells. They are found mainly in the dermis under the nail bed (90-500 / mm2). They are encapsulated oval structures with a length of about 300 μm. Globular bodies contain curved arterial and venous vessels, nerves and a capsule that is formed by modified, large, cholinergic muscle cells and cholinergic nerves. Globules provide adequate blood supply to the fingers even in the cold.
The digital arteries are accompanied by a pair of digital nerves. Their terminal branches innervate the nail bed and the nail matrix, and their distal branches nerve the periungual tissues through multiple nerve endings, and with the highest density in the nail folds. This rich inertia also explains the strong pain of injury to peri-and-sanguinous tissues.
 
Nail development
 
The embryonic development of the nail apparatus begins during the 9th gestational week. From the same primitive epidermis, from which the hairs and sweat glands originate. Nails are used as a diagnostic criterion for determining the length of pregnancy. It is believed that the development of the nails, as in the hair, is responsible for neuroectodermal-mesenchymal interaction.
 
 
 
Maria Georgieva - Artistic Director