Hair is the strands that cover the human body. It provides various functions, such as regulating temperature, protecting the skin, ensuring a sense of touch, expressing personality, and acting as a visual and tactile stimulus. Its primary purpose is to trap air for insulation. It is also used as a defensive mechanism. It is made up of dead keratinized cells. It can be thick or thin, long or short, matte or glossy, and curly or straight.
The outermost layer of hair, known as the cuticle, is composed of scale-like cells that provide protection and a smooth surface. These cells have a protective function against physical and chemical insults. They move in an upward direction to form a protective layer that extends over the hair follicle. These cells are approximately 60 micrometers long and 6 micrometers wide.
The innermost layer of hair, the cortex, is comprised of macrofibrils and contains melanocytes, which produce melanin pigment. It is connected to the medulla by intercellular cement, which is rich in proteins and lipids. The medulla and cortex are part of the hair shaft, which is a hard filamentous strand that stretches over the skin.
The medulla contains a specialized cell, the melanocyte, which produces melanin pigment and injects it into the developing hair shaft. This pigment protects the hair from damage and serves as a camouflage.
The hair bulb is located at the base of the follicle. It is surrounded by nerve fibers and serves as the root of the hair. The base of the follicle is also a source of nutrients and minerals for the cells inside the follicle.
The hair grows in a continuous cycle. The growth phase is known as the anagen phase. During the anagen phase, the cells in the hair matrix and follicle go through mitotic activity. The growth phase is dependent on the age and nutritional status of the follicle. This phase may be interrupted if the hair is damaged.
The follicle contains sebaceous glands, which produce a lipid-rich substance called sebum. The follicle also contains arrector pili, a smooth muscle that contract when the sympathetic nervous system sends a message to make the hair stand up. The follicle then undergoes rest periods. The follicle is a unique miniorgan, which consists of numerous layers of cells that are not visible when the skin is in its normal state.
The follicle is located in the skin’s dermis. It is one of the immune privileged sites. This structure is formed when a cellular layer, the follicle, forms at the junction of the hypodermis and deep dermis. The follicle can grow to several thousand millimeters in length. The diameter of the follicle is determined by the size of the base cells. The color of the follicle is the same as that of the skin. The follicle has many genes that play a significant role in its development.
The follicle is composed of three primary zones: the cortex, the medulla and the pith. The size and shape of the medulla and cortex determine the texture of the hair. The texture of the hair is determined by the shape of the medulla and the angle of the hair shaft.