When we think of our hair, we think of the hard filamentous portion that extends above the surface of the skin. The hair shaft is made of three layers, each with a distinct function. These layers are known as the cuticle and follicle. The cuticle layer protects the pigments that give our hair its color. We can feel the cuticle by pinching a strand of hair and running your fingers along it.
The different types of hair on the body include vellus hair, eyebrows, and terminal and alopecia. Lanugo is the thin, fluffy hair that grows in the third or fourth month of fetal life, and it sheds shortly after birth. Lanugo, or down hair, covers the undersurfaces of the fingers and toes and is found on every part of the body except the palms. These hairs can regenerate without scarring.
The follicle is the root of each hair. It extends from the skin’s surface and lies deep into the dermis layer. The follicle has a sebaceous gland that secretes a lipid-rich substance called sebum, which protects the hair and moisturizes the scalp. The hair follicle is made up of several layers, including the inner root sheath, which contains the hair strands.
The texture of the hair plays a role in its ability to be curled or straightened. Curly hair is generally very receptive to different styles, but can become brittle and resistant to styling. The hair texture of a particular subculture can tell us a lot about its personality. Hippies, metalheads, and Indian sadhus often sport long, flowing hair. Punks, on the other hand, wear spikes and mohawks. Skinheads have short, cropped heads. Younger indie kids, meanwhile, often sport long, stylized bangs.
In addition to the cuticle, the hair shaft is composed of two or three layers – the cortex and medulla. The outermost layer is the cuticle, and it consists of flat, overlapping cells. The cuticle protects the shaft and gives the hair its distinctive look. It also carries oils, nutrients, and pigments. These three layers give hair its shape and color. The cortex and cuticle work together to produce the hair we see on our heads and other parts of our body.
Humans evolved with hair on their head to protect the scalp from UV rays and harsh environments. The function of hair in other parts of the body is debated. Despite this, humans still need to wear hats when they go outside in cold weather. Some argue that a hairy shoulder would be beneficial to the brain, which is extremely sensitive at birth. And, in ancient times, axillary hair in the underarms served a protective purpose as a sign of sexual maturity.
A good example of this is the shape of a human hair follicle. A round follicle produces straight hair, while an oval-shaped follicle creates curly hair. Melanin is the pigment that gives hair its color. Melanin is stored in the hair follicle and is present in two types – eumelanin and pheomelanin. There are many different types of melanin, but in general, the oval follicle produces straight, shiny hair.