Structure and Function of Nails and Skin Innervation

‭Structure and Function of Nails and Skin Innervation‬ ‭➔‬ ‭-The nail:‬ ‭The nail is a structure deriving from the epidermis, it is a plate of epithelial cells. keratinized which‬ ‭are located at the level of the dorsal surface of each distal phalanx and there are several parts to‬ ‭these nails:The root of the nail is the part that penetrates into the epidermis and there is a classic‬ ‭epithelium which covers this root with the stratum corneum etc. There's the tablet which rests on‬ ‭the epidermis which we call the nail bed and this tablet comes from the differentiation of an area‬ ‭which is called the matrix, ventral or dorsal, matrix which is in depth at the root level and it is these‬ ‭cells at the matrix level which will multiply, divide which will migrate and which will keratinized‬ ‭and this formation is important because we recognize that nail formation is rapid. The outermost‬ ‭part of the tablet separates from the bedgle, frees itself from him, and this tablet although very rigid‬ ‭and protecting the dorsal side of the last phalanx, this tablet is transparent and the epidermis of the‬ ‭nail bed is very thin which means that we can see the connective tissue through the nail.tif, the‬ ‭dermis and therefore we can see the vascularization, the oxygenation of the blood by observing the‬ ‭dermis, the connective tissue under the nail. The nail plays a role in tactile perception.‬ ‭➔‬ ‭-Innervation of the skin:‬ ‭It is important because the skin is very rich in nerve endings because the skin is the organ of touch,‬ ‭a sensory organ and it is a major function of the skin which is the collection of information coming‬ ‭from the outside. There was an important function which is the function of defense of which we‬ ‭spoke and there is this function of organ of tact. There are many different constituents that come‬ ‭together to form the innervation. There are book endings, encapsulated, there are vegetative,‬ ‭motor, cerebrospinal nerves etc.‬ ‭➔‬ ‭-Free nerve endings:‬ ‭There are myelinated fibers which will lose their myelin sheaths before branching or often which‬ ‭lose their myelin sheath before branching or often which lose their myelin sheath as it passes‬ ‭through the basal lamina of so they are myelinated in the dermis and which become unmyelinated‬ ‭in the epidermis and these endings can go up to the level of the stratum corneum and therefore‬ ‭completely cross the epithelium. There are unmyelinated fibers often of small diameters (1 micron‬ ‭in diameter) which have multiple branches and there often the Schwann sheath in which finds its‬ ‭unmyelinated fibers stops before the basal lamina so here again the envelope of the Schwann sheath‬ ‭exists in the dermis then it disappears when the fiber is passed through the basal lamina. These‬ ‭unmyelinated fibers are largely responsible for sensitivity to pain and temperature differences and‬ ‭then there are fibers related to hair which are numerous:80% of the fibers of a cutaneous nerve are‬ ‭intended for hairs so around each hair follicle of a hair, there are very many nerve endings. These‬ ‭fibers in relation to the hairs are also‬ ‭ yelinated fibers than unmyelinated fibers therefore at the level of the hair itself, of the follicle‬ m ‭these are unmyelinated fibers so they have lost their myelin sheath prior. These fibers are‬ ‭sometimes so numerous that they form a kind of sleeve around the hair follicle. In fact, a single‬ ‭axon can make endings nervous for several dozen hairs. The activation of these fibers is directly‬ ‭linked to the mobilization of the hair.‬ ‭Alongside these simple, free nerve endings, there are encapsulated endings: we also call these‬ ‭associated fibers or tactile corpuscles and these tactile corpuscles are essentially the‬ ‭mechanoreceptors of the skin.‬