The Basics of Hair


Hair is a biological material that grows from follicles in the dermis. Human hair has three major components: a follicle, the keratin-containing cortex and the cuticle. These components are essential to the health and growth of human hair. The hair follicle is a tube-like pocket in the epidermis that surrounds a tiny area of dermis at its base. The follicle produces hair by dividing cells that are pushed upward from the base. These cells are keratinized and then undergo pigmentation to create hair.

Hair is an important part of mammals’ survival. It serves many functions, including thermal regulation, protection from UV radiation, and camouflage. It also extends the sense of touch beyond the skin. It also serves a protective role, as guard hairs give warning signals when an animal is in danger. Polar bears, for instance, use fur to help regulate body temperature. Their black skin and fur can be seen through snow to hide their cubs from predators.

Hairs are composed of three types. The first is called the lanugo, and it begins to grow during the third or fourth month of fetal life. Older hairs are shed from the body when it is time to grow new hair. The second type is called the vellus, and it covers all parts of the body, except the palms, soles of the feet, and undersurfaces of the fingers.

Men have more hair on their heads than women do. According to Jablonski, a head covering with hair protected the scalp from the intense UV light that is common in Africa. Others believe that the lack of hair on the shoulders was advantageous to pre-humans because the head is the seat of the brain and highly vulnerable to injury during birth. In addition, underarm hair, or axillary hair, is maintained as a sign of sexual maturity.

Microscopic analysis of hairs can be helpful in identifying the origin of a hair sample. Microscopic characteristics like the thickness of the cuticle and variation of its thickness are helpful for comparing different types of hairs. Using a punch card and checklist, a hair sample can be compared to a known hair sample. If the two samples have similar microscopic characteristics, the results can help determine whether a sample is human or nonhuman.

Hair color depends on the pigment granules in the hair. Other physical properties of hair also influence how it transmits light. Hair color can be useful for comparing different types of hair. Hair color can vary between two individuals due to differences in exposure to various elements. But, the difference between two individuals is usually far less than the difference between the two types of hair.

In the forensic field, hair identification is not only important for identifying a suspect or a victim. It is also an important tool for textile conservators, wildlife biologists, and archaeologists. Many researchers have studied the morphological characteristics of hairs and developed keys for identification. Researchers have also reviewed animal-hair identification, providing descriptions of microscopic features in the hair.