Dictionary > Terminal hair

Terminal hair

Definition
noun
The mature type of hair characterized by being pigmented, thicker, and with a larger diameter than the other hair types such as lanugo and vellus hair
Supplement
Terminal hair is the mature type of hair of humans and other mammals. It is thick, coarse and pigmented. The human terminal hair fiber has a diameter of about >60 μm. It can also grow more than 2 mm in length.1
In humans, the first type of hair that grows on the skin is the lanugo. Lanugo forms in utero and is usually shed before birth. It is then replaced by vellus hair, i.e. the type of hair that is very fine, soft, and non-pigmented. Typically, the vellus strand is <30 μm in diameter and <2 mm in length.1 The vellus hair is the type of hair that covers most of the body at childhood to adulthood. At puberty, vellus is replaced by terminal hair in certain parts of the body.2 The increase of androgen levels causes the replacement of vellus hair by the mature, dark, and coarse terminal hair especially in body parts that are sensitive to androgens. Examples of these body parts are the pubic area and the armpits where pubic hair and axillary hair develop, respectively. In males, there are more body parts that are sensitive to androgen, and therefore grow terminal hair, e.g. facial hair, chest hair, abdominal hair, etc.
See also:

Reference(s):

1 Peytavi, U. (2008). Hair growth and disorders. Berlin: Springer. p.9

2 Hiort, O. “Androgens and Puberty”. Best Practice & Research Clinical Endocrinology & Metabolism 16(1): 31–41.


You will also like...

Flowers and tiny fruits of the pomegranate plant
Fruits, Flowers, and Seeds

This tutorial deals with the structure and function of flowers, fruits, and seeds. Also included here are the types of f..

Stem
Stems

Stems primarily provide plants structural support. This tutorial includes lectures on the external form of a woody twig ..

Salmon jumping upstream in the river
Lotic Communities & Animals

A running water environment offers numerous microhabitats for many types of animals. Similar to plants, animals in lotic..

Chemical composition of the body
Chemical Composition of the Body

The body is comprised of different elements with hydrogen, oxygen, carbon, and nitrogen as the major four. This tutorial..

Peppered moth ("Biston betularia") melanic and light form
Examples of Natural Selection

Darwin's Finches are an example of natural selection in action. They are an excellent example of the way species' gene p..

Biological Energy
ATP & ADP – Biological Energy

ATP is the energy source that is typically used by an organism in its daily activities. The name is based on its structu..