The social significance of hair is immense. Human beings have several types of hair, including lanugo (downy) and vellus. Lanugo grows on most external areas of the body. However, hair on the palms of the hands and soles of the feet cannot grow. Only the face and eyebrows have hair, and both types are subject to trimming and other treatments. Moreover, both sexes have distinctly different patterns of body hair.
The shaft is made up of three layers, the cortex, the cuticle, and the medulla. Each layer is a distinct type of cell and is arranged in a scale-like arrangement. In humans, the outermost layer is the cuticle, which is a single layer of cells arranged in a circular pattern. Each layer serves a specific purpose. The cuticle protects the cortex and medulla from chemical and physical insults.
The skull of the semi-aquatic therapsid Estemmenosuchus shows glandular depressions and smooth skin, but it is not useful for identifying terrestrial integument. The fossil Castorocauda, a late middle Jurassic, haramiyid, bears a series of transverse rows of rectangular scutes, similar to those of modern crocodiles. The fossils of synapsids cannot be earlier than 299 ma.
The development of hair involves the growth of three layers: the cuticle, the cortex, and the medulla. The cuticle cells are square and flat, and adhere tightly to the cortex cells. As hair grows upward, the cells in the medulla die and are cut off from the nourishment of the hair follicle. As the hair grows upward, it undergoes a process known as keratinization, where keratin is added to the shaft.
Hair is an important part of the body and is a natural protection against the harsh UV rays of the equator. It is a sign of sexual maturity. And in contrast to the axillary hair in the underarms, the head has a very fragile structure. Its origins can only be established through the analysis of fossils. The earliest mammals had a thick, curly coat and had a lot of follicle-stalk-like scutes.
The origin of hair is unknown, but it is known that it has two or three layers: the cortex and the medulla. The cortex is the innermost layer of the follicle, while the medulla is the outermost layer. Both layers contain a large amount of melanin, which is responsible for the color of hair. The medulla and the cortex are connected through a network of fibers.
The color of hair comes from the pigment melanin. Lighter hair has more melanin than dark hair. People with dark skin have more melanin than light skin, and those with light skin have less melanin. This pigment is necessary to create the colors we want. We need to keep the melanin in our bodies in order to look our best. But if you’re prone to developing gray or white hair, it may be time to start coloring it.