Hair is made up of two parts: the follicle and the hair shaft. The follicle is a living structure where hair is produced and nourished. The hair shaft is a thin flexible cylinder that contains pigments that are responsible for the color of your hair. The hair shaft grows out of the follicle and is visible on the outside.
Hairs are an essential part of the body and function as a source of heat insulation, protection from UV rays, and a means of camouflage. Hair is also important for sexual recognition, and differing patterns in hair provide different benefits. In addition to insulating the body, hairs also help animals detect touch. For example, the hairs on a porcupine’s nose are used as sensory organs.
A typical mammal hair consists of a follicle with a root located beneath the surface of the skin. Hair consists of columns of keratinised cells that are pushed upward from the follicle base. The follicle is connected to the glassy basement membrane, which helps sebum to flow out of the gland.
Human hair consists of three different types. The smallest is called the lanugo, and starts to grow in the third or fourth month of fetal life. It is shed before birth, while the rest sheds shortly after. The rest of the body is covered by vellus, also known as down hair. It covers every part of the body except the palms, soles, and undersurfaces of the fingers.
Hairstyles vary significantly between cultures and social groups. In early modern China, the queue, which is a male hairstyle, was popular among the Han Chinese and Manchus. The queue’s purpose was to mimic male-pattern baldness. Hair on the front of the head was then braided into a long pigtail.
Hair follicles are microscopic structures that are located in the skin. A hair follicle contains a sebaceous gland, which produces sebum, a lipid-rich substance that protects the hair and moisturizes the scalp. Hair follicles also contain a hair bulb, which is the living part of the hair. When the bulb matures, it produces hair, which appears as a strand of hair above the skin.
Hair growth is cyclical, with the follicle undergoing growth, resting, and shedding phases. Each of these phases lasts about two to three months. During the growth phase, hair follicles undergo rapid cell division. Once this happens, new hairs begin to protrude from the scalp. The next phase, called catagen, is a transitional phase during which the follicle produces less pigment. The final phase, called telogen, lasts about three to four months.
The evolution of hair can be traced back thousands of years. The earliest known hair remnants were found in the Paleozoic period. However, this evidence does not necessarily confirm that human hair existed millions of years ago.