Vellus hair

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Cross-section of human skin showing vellus hair

Details
Synonyms
Pronunciation
Carnegie stage
Days
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Gives rise to
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Vellus hair is a type of fine, thin hair that covers most of the human body. It is often referred to as "peach fuzz" due to its soft and downy texture. Unlike terminal hair, which is thicker and more pigmented, vellus hair is usually short, light-colored, and barely noticeable.

Structure and Function

Vellus hair is characterized by its small size and lack of pigmentation. It typically measures less than 2 mm in length and is less than 30 micrometers in diameter. Vellus hairs are anchored in the dermis layer of the skin and are associated with sebaceous glands, which secrete oils that help to protect and moisturize the skin.

The primary function of vellus hair is to provide a layer of insulation and to help regulate body temperature. It also plays a role in the sensory perception of the skin, as it can detect light touch and vibrations.

Development and Distribution

Vellus hair begins to develop during the fetal stage and continues to grow throughout childhood. During puberty, many vellus hairs are replaced by terminal hairs in certain areas of the body, such as the face, armpits, and pubic region, due to the influence of androgens.

In adults, vellus hair covers most of the body except for areas such as the palms of the hands, soles of the feet, and certain parts of the external genitalia. The density and distribution of vellus hair can vary based on genetic and hormonal factors.

Clinical Significance

Changes in vellus hair can be indicative of certain medical conditions. For example, an increase in vellus hair can be seen in anorexia nervosa, where the body grows more vellus hair as a response to decreased body fat and insulation. Conversely, a decrease in vellus hair can occur in conditions such as alopecia areata.

Also see

• Terminal hair
• Lanugo
• Hair follicle
• Sebaceous gland
• Integumentary system