ABSTRACT
The hair appendage is an important part of human skin. Nearly the whole surface
(approximately 90%) of the human body is covered with hair, and the total
number of hairs on the body surface of an adult is impressive: Approximately
5,000,000 hairs can be found there of which 100,000 to 110,000 cover the scalp
at a density of 175-300 hairs/cm2 (1). During mammalian evolution, hair had an outstanding biological importance in regulating various physiological processes
(Table 1). As stratified epithelium, hair generally provides protection against heat
loss and environmental influences, such as mechanical injuries or ultraviolet
(UV) irradiation from sunlight. Other important functions of hair are the indication
of sexual development of an individual, enhancement of attractiveness, and social
communication. Hair also functions as a sensory organ, which can be deduced from
the fact that various hair follicles are connected with a complex nerve network that
provides sensory information about the environment.
