What are hair follicles?: The hair follicle is an active organ of the human body. It is found in the dermis layer of the skin. It is made up of twenty different kinds of cells. Each such cell has its own significant function. It controls the growth of hair with communication between hormones, neuropeptides and immunity cells.
The hair follicle is an interesting topic of study, on basis of its contradictory nature in developmental biology and medicine. Since the time of early civilisations, hair has been a part of society. In different eras, there were different styles of hair implemented for different strata of the society. Around the world, hair has been marked with culture. For certain rituals or on completion of such rituals, the participants were supposed to adopt a certain hairstyle. For example, during the 15th century, women who were charged with adultery were first purified and then only half of their hair was shaved. This was done to mark them as adulterers. Hair is important to defining facial structure and appearance. The hair of our scalp protects us from harmful UV rays. It also acts as an insulator against extremities of weathers. The hair follicles are unevenly distributed in our body. While some parts like lips or palms of our hands don’t have any, our groin and scalp are filled with numerous hair follicles. The ethnicity of a person can be determined on the basis of their hair follicle.
Structure of a hair follicle
The papilla is a large structure at the base of the hair follicle. The papilla is made up of connective tissues and capillary tube. Cell division in the papilla is unknown. Hair matrix is found around the papilla.
A root sheath is made of two different layers, an external and an internal layer. The external root sheath is made of empty cuboid cells. The internal layer is divided into three layers. These are the Henle’s layer, Huxley’s layer, and an internal cuticle that continues with the outer hair fibre layer.
Then comes the bulge, located on the outer layer at the joining of arrector pilli. It contains the stem cells. These cells help in the production of new cells for the whole hair follicle. It also helps in healing of wounds on the epidermal layer.
The arrector pilli is a bundle of smooth muscular fibres found only in mammals. It is attached to a unit (number of) hair follicles. These muscles contract due to cold or fear, which causes stimulation of the sympathetic nervous system. This results in piloerection or goose flesh, popularly known as goosebumps. The main function of this in mammals is to help to trap heat in the skin and to maintain body temperature. It is also known to force the production of sebum for protection of hair follicle due to the contraction.
The sebaceous glands are attached to the hair follicle. It produces a waxy or oily substance called sebum. The higher the density of the hair, the more sebaceous glands are found.
Such a tiny sac has so much importance for the hair in the human body in general. Such organs make the study of the human body fascinating.