A hair follicle is that sac-like anatomical structure from
which a hair grows, enclosing the hair root.
Each follicle consists of the dermal papilla (DP). This part has a
healthy pear shape in normal hair follicles. This connective tissue
consists of a highly active group of cells responsible for the production
of hair fiber.
Cell division is applicable to hair growth
as well. In this case, the cells near the dermal papilla are an
actively proliferating group of cells. These cells are known as
the cortical or matrix cells. When these epidermal cells divide
rapidly during the Anagen or the growth phase of the hair follicle,
the resultant growth is pushed up to the follicle. This then becomes
the hair shaft that protrudes above the skin surface.
The keratinized hair fiber and associated products are formed through the differentiation of the epidermal cells and through the dermal papilla. This consists of several layers: the cortex, the surrounding hair cuticle and the medulla.
On the other hand, the hair root which is enclosed by the hair follicle is surrounded the inner and outer root sheath. There are three layers dividing the inner root sheath. These are the cuticle, the Huxley layer and the Henle layer. The outer root sheath, on the other hand, is distinct from other epidermal components of the hair follicle being continuous with the epidermis. What separates the outer root from sheath from the dermal sheath is the basement membrane. This glassy membrane provides a physical division between the epidermal and dermal cells.
Hair follicles, as with any part of the body, can also be plagued by infections
caused by several factors present in the environment. Some of the
most common hair follicle infections are furuncles, folliculitis
Folliculitis is a superficial infection caused by the staphylococcus aureus bacteria or the application of oils and other similar products to the skin. Minor cases of folliculitis may be cured without any form of treatment. Folliculitis, when not treated properly, can lead to furuncles. Application of oil to the skin may also cause folliculitis.
Furuncles are the most common hair follicle
infection. This skin infection, also referred to as boil, is
caused by staphylococcus bacteria. This particular type of bacteria
is normally found on the surface of the skin. These bacteria seep
through the tissues of the follicle and the subcutaneous tissue,
damaging the hair follicle. Common areas of the body affected by
this infection are the face, neck, armpit, buttocks, and thighs.
Furuncles can occur individually or in multiples and can be very
painful on some areas such as the ear canal or nose.
Carbuncles, caused by a condition known as carunculosis, are characterized by the expansion or joining of furuncles that develop close together.