Hair
Hair
Hair (/hɛər/; from Old English hǣr) is a protein filament that grows from follicles found in the dermis, or skin. Hair is one of the defining characteristics of mammals.
Etymology
The word "hair" comes from the Old English hǣr, from Proto-Germanic *hēran, which is related to the Old High German hār, and the Old Norse hārr.
Structure
Hair is made of a tough protein called keratin. A hair follicle anchors each hair into the skin. The hair bulb forms the base of the hair follicle. In the hair bulb, living cells divide and grow to build the hair shaft.
Types of Hair
There are three types of hair on the human body:
- Vellus Hair: This type of hair is soft, fine, and short. It is generally light-colored and can be found all over the body.
- Terminal Hair: This type of hair is long, thick, and dark. It is found on the scalp, armpits, and pubic area.
- Lanugo Hair: This type of hair is very thin and soft. It is usually shed before birth.
Functions
Hair has several functions:
- Protection: Hair protects the scalp from the harmful rays of the sun and helps to keep the head warm.
- Sensory function: Hair follicles contain nerve endings, making hair an important sensory organ.
- Regulation of body temperature: Hair helps to regulate body temperature by trapping warm air close to the skin.
Related Terms
- Alopecia: This is a condition in which hair is lost from some or all areas of the body.
- Hirsutism: This is a condition of unwanted, male-pattern hair growth in women.
- Hypertrichosis: This is a condition characterized by excessive hair growth on areas of the body where hair does not normally grow.
External links
- Medical encyclopedia article on Hair
- Wikipedia's article - Hair
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