Unlike the human skin, which is a thin, pliable, elastic tissue, hair is a tough protein filament. It is mainly made of keratin. It protects the body from physical damages, scratches, and other external insults. It also serves as a camouflage. Depending on the number and type of white hairs, it can vary in color.
There are three main layers in the hair shaft: cuticle, medulla, and cortex. The cuticle is the outermost layer, and it is made of flattened cells. These cells have various functions, such as protection against chemical insults and removing dirt. It is found in all parts of the body.
The medulla is a soft mass of tissue. The outer root sheath is a connective tissue sheath that extends from the epidermis to the hair bulb. The hair follicle is a stocking-like structure under the skin. It is composed of special cells that reproduce to produce new hair cells. The follicle is covered by a thick connective tissue sheath, which forms a glassy membrane that surrounds the hair follicle. It is generally keratinous in the upper regions of the follicle and becomes multilayered in the region of the upper hair bulb.
The cortex is the inner part of the hair strand. The proteins of the cortex are coiled in a curly telephone cord-like pattern. As the strand is stretched, the coiled proteins straighten. The fibers then protrude from the outer skin layer. The cortex is surrounded by a follicular anchorage of square cuticle cells that are adhered to the cortex cells proximally. The overlapping of the cuticle and the cortex is like tiles on a terra-cotta roof.
The hair bulb is the base of the follicle. The follicle contains cells that produce new hair and nourishes them with blood. The follicle is also the site of many nerves that sense hair movement. The nerves are sensitive to a slight draft and deliver signals to other animals. The follicle also contains oil glands. The papilla provides blood supply to the hair root. It is also the site of a large number of nerves that terminate in the follicle.
A hair follicle can be damaged by several different types of diseases, including trichomycosis nodularis, Staphylococcus aureus, and folliculitis. The follicle is also a source of genetic material, which can be used to trace a person’s ancestry. The DNA in a hair follicle can be used to determine paternity. In addition to determining a person’s biological father, it can be used in crime investigations.
There are several types of mammals, including humans, that have hair. Some of the most common types are fine vellus, coarse vellus, and terminal hair. The amount of melanin in the hardened hair cells determines the color of the hair. Its thickness and location can vary depending on the individual. As the hair ages, the melanin decreases. Some of the more specialized forms of hair include hedgehogs, which have modified hairs.
The most common interest in hair is geared towards its growth and appearance. Depending on the age and nutritional status of a person, the follicle may go through different phases. The duration of these phases is determined by the location of the hair and the hormonal status of the follicle.