Hair anatomy

Hair Anatomy

The human hair is a complex structure that plays a significant role in social and sexual communication. It is made up of two main parts: the hair follicle, which is embedded in the skin, and the hair shaft, which is visible above the scalp.

Hair Follicle

The hair follicle is a tunnel-shaped structure located in the epidermis (outer layer of the skin). It extends down into the dermis, the second layer of the skin. The hair follicle is responsible for hair growth and the color of the hair. It contains several components including the papilla, which is made up of connective tissue and a capillary loop. Cell division in the papilla is either rare or non-existent. Around the papilla is the hair matrix, a collection of epithelial cells often interspersed with melanocytes.

Hair Shaft

The hair shaft is the part of the hair that is visible above the skin. It is made up of three layers: the cuticle, the cortex, and the medulla. The cuticle is the outermost layer. It is composed of flat, thin cells that overlap like the tiles on a terra-cotta roof. The cortex, the thickest hair layer, contains the hair's pigment, giving it its color. The medulla, the innermost layer, is not always present and is considered the most soft and fragile part of the hair shaft.

Hair Growth Cycle

Hair growth occurs in cycles consisting of three phases: anagen (growth phase), catagen (transitional phase), and telogen (resting phase). Hair actively grows during the anagen phase, which can last several years. During the catagen phase, which lasts about two weeks, the hair follicle shrinks. During the telogen phase, which lasts around one to four months, the hair rests.

Hair Types

There are three types of hair: lanugo, vellus hair, and terminal hair. Lanugo is the first hair produced by the fetal hair follicle, and it usually disappears before birth. Vellus hair is short, thin, slight-colored, and barely noticeable thin hair that develops on most of a person's body during childhood. Terminal hair is the fully developed hair, which is generally longer, coarser, thicker, and darker than vellus hair.

See Also

• Hair loss
• Hair color
• Hair care

References

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