Appendages of the skin
Appendages of the skin
Hair- The hair is just the modified (developed) form of the tough part of epidermis that is located in the dermis. It is a tube like structure, but the shape, size and formation depend on physical convenience (utility). In it too, nerve fibers are absent like the cells of different skin layers, but the hair is associated with blood vessels and nerve fibers, hair follicles and the root area, which are situated in the deep of the dermis. So, when hair uprooted from root by pulling, one feels pain.
Every hair is situated in a hair follicle. On the basis of hair follicle, there is a bunch of cells found, called hair bulb. Hairs grow by the growth of the cells of this hair bulb. In the bottom of hair follicle, a small funnel shaped elevation (protuberance) is present, known as papilla, in which vascular papilla a bunch of blood vessels found. The growth of hair depends on its blood. During hair growth, as well the cells of hair bulb are pushed upwards far away from the source of nutrition as is being died and converted into keratin. The hair remains rooted always as oblique position in the skin. Small involuntary muscle-arrector pilorum remains connected with hair follicles. It always present toward the direction of sloped hair so that the hair could remain stand straightly when it contracts. The skin around the hair is also being pulled up at that time, known as goose flesh.
The part of the hair above the skin (that can be seen) is called hair shaft and the remaining part of it present inside the skin is called hair root. The upper most layer of the hair shaft is called cuticle, which are made up of overlapping scale like cells. A medulla of the hair is found inside every hair. The cortex of the hair is wide (thick) at bottom and narrow at top. The hair root is situated on the papillae and the hair gets its nutrition only from here. The health, growth and originating depends only on the activeness and healthiness of the papilla.
In the hair follicle, the dermis part is ativahikamay and more inspired from nerve fibers than other parts. One sebaceous gland is related to each of hair. A type of oily fluid named sebum goes on secreting from it all the time that keeps the hairs and skin smooth.