The Hair follicle consists of the inner and outer epithelial root sheaths derived form the epidermis and connective tissue sheaths derived form dermis.
- The inner epithelial root sheath
- cuticle of root sheath similar to the cuticle of hair and lies against it.
- Huxley’s layer consisting of several rows of elongated cells, the cytoplasm containing eleidin-like granules.
- Henley’ layer-a row of flattened clear cells.
- The outer epithelial root sheath is a direct continuation of stratum germinativum to which it corresponds is structure.
- The connective tissue sheath is derived from dermis and consists of three layers. An inner layer of Vitreous membrane, a homogenous, narrow hyaline band, a middle layer of connective tissue fibres arranged circularly and an outer layer of loosely arranged collagenous fibres, running longitudinally.
- All these different layers can be clearly seen only in the deeper portions of the root, a little above the bulb but below at the level of the bulb and above in the upper part of the root and shaft the different layers cannot be clearly demarcated.
- The Hair bulb is not organized into layers but constituted a matrix of growing multiplying cells, which superficially become transferred into the horny cells of the hair and inner root sheath. It is in the form of bulbous thickening which surrounds the dermal papilla. Laterally, cells of the bulb become continuous with the outer root sheath.
- The papilla of the hair is similar to other papillae and consists of delicate elastic and collagenous fires, cellular elements and capillary loops.
Muscles of the hair follicle
- The errectores pilorum, the errectors of the hair are oblique bands of smooth muscle fibres, which arise in the subepithelial tissue and are inserted to the connective tissue sheath of the hair follicle about middle of the follicle. The muscle usually arches around the sebaceous glands, which fill the angel between the muscle and hair. The muscle is poorly developed in certain regions like axilla, face etc. and are absent in eyelashes etc.
- The contraction of the muscle caused the hair to become more vertical to the surface and a small depression appears in the skin at the place where the muscle is attached. This gives rise to the so called “goose flesh”.
Color of hair
- It is due to the presence of pigment granules found in and between the cells of the cortex of the hair.
- Presence of air also modifies the colour to a certain extent and hair in which pigment has faded and the medulla has become filled with air appears silver white.
