The hair you see on your body is basically dead. That is why it doesn't hurt when you get your hair cut at the salon. However, the actual structure of hair is quite complex. Hair is composed of a hard, fibrous protein called keratin. Each strand of hair consists of three concentric layers: the cuticle, the cortex and the medulla. Each of these layers has its own unique structure and function.
Cuticle
The outer layer of hair is called the cuticle. It is a thin and colorless covering consisting of overlapping keratin scales. The packed dead cells that surround this layer are known as the cuticular layers of the hair. They protect the middle layer of the hair, called the cortex. Kertain is the same protein that makes up fingernails and toenails, protecting the outer layer of skin. There are three basic scale structures that make up the cuticle: coronal or crown-like, spinous or petal-like, and imbricate or flattened. Coronal scale patterns are found in very fine hairs, rarely seen in humans.
Cortex
The middle layer of hair is the cortex. The cortical layer is created from keratin proteins formed from a series of helical structures packed together in strictly defined geometries. The cortex is responsible for the strength, color and texture of the hair. The shape of the cortex determines if your hair is straight or curly; a cortex with a round cross-section produces straight hair, while an oval-shaped cortex produces curly or wavy hair.
Medulla
The innermost layer of hair is called the medulla. The medulla is found only in large, thick hairs. It reflects light, giving various tones and shades to hair color. Inside the medulla is the medullary canal, which is part of the excretory system. It can store and contain materials released by the body, including foreign debris, heavy metals, and medications metabolized by the body.
Hair Root
Enclosed within a hair follicle is the hair root, found below the surface of the skin. The dermal papilla is located at the base of the hair follicle and is fed by the bloodstream carrying the nutrients to produce new hair shafts. The dermal papilla contains receptor androgens, which regulate hair growth.
Terminal Hair
Terminal hair refers to the dark, very visible hair we see. Follicle health determines terminal hair visibility and thickness. If you are bald, most likely thick hair as been replaced by very thin hair, the follicle having been decreased in size, or damaged in some way, such that it is no longer able to produce terminal hair.
Hair Color
Melanin is the pigment responsible for hair color. There are two kinds of melanin: eumelanin and pheomelanin. Eumelanin creates brown or black hair while pheomalanin creates red heads. Blondes have very low amounts of melanin, while gray hair is the complete lack of melanin.
Member Comments