Different Hair Shaft Layers And Their Role

Usually hair grow by an inch or half inch within a month. Our scalp consists of 5 layers among of which, a hair follicle lies in the second layer with a depth of 4mm.

Hair root is named as Papilla that is actually an oval material with fibroblasts. Papilla controls the hair length. The lower point of Papilla is associated with the fibrous root cover that encloses the hair and combines to the skin. Papilla is covered by the matrix cells as well as melanocytes. The matrix cells reproductive cells. On the top of matrix, different hair layers can be distinguished. Beginning from the mid of hair and going outward, the hair shaft medulla, cortex, cuticle develop the hair shat that end from the skin surface in the form of hair.

Scalp hair is covered by the internal follicle cover, exte
al follicle cover, vitreous layer and fibrous root.

A hair comprises of a muscle called as Arrector pili that begins from below the surface and is connected to the outer sheath of hair, the fibrous root, by 45% of the hair length. A hair has its 55% length under the arrector pili.

Above this pili muscle sebaceous gland is present whose duct opens in the hair canal, the sebaceous duct unlocks at 20% length of hair from the skin.

Hair length can be categorized into three tiers. Hair under the arrector pili is named as lower part. Above area of the pili and under the opening of sebaceous duct is named as middle part. Above the sebaceous duct, skin level is present from which the hair ends and is named as upper part.

The upper part and isthmus make the permanent part of the hair as it is isolated throughout the hair growth cycle. The lower part of hair undergoes failure and redevelopment throughout the life.

The interal root cover is a potential layer that acts a mold for the developing hair. This cover begins from the matrix cell and ends above the insertion of arrector pilli.

The exte
al root cover begins at the matrix lever, enclosing the internal root and goes above the arrector pilli combining into the skin. The stem cells in hairs are distributed throughout the outer root particularly up to arrector pilli insert.

The fibrous root cover encloses the whole hair shaft and merges into the skin.

All hairs grow in the form of follicular units.