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There are four parts of the hair: the follicle, the cuticle, the cortex and the medulla. On average, each hair strand grows about six inches per year and then dies, usually before four years.
Follicle
The follicle is the portion of a strand of hair below the level of the skin. This is where hair begins and where it receives the nutrients it needs to grow and survive. The arrector pili and the sebaceous gland are considered part of the hair follicle, they are small muscle fibers attached to each hair follicle. They cause hair to stand up by contracting. they contract involuntarily in cold weather, causing “goose bumps.”
The sebaceous gland delivers sebum to the follicle. Sebum is a greasy substance that lubricates hair and keeps it soft.
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Cuticle
The cuticle surrounds a strand of hair, it acts like a roof. It determines how hair reflects light, its sheen. It consists of scales that grow and point towards the tip of the hair, sometimes five to twelve layers deep. The cuticle is translucent; even though it is on the outside, it is not the source of hair color. It blocks moisture from leaving the hair shaft. It also slows down entry of substances (water/oils/conditioning agents) and it protects the shaft from damage The cuticle protects the cortex inside.
Cortex
Inside the cuticle is the cortex which is responsible for most of the hair’s width, weight and visual properties. It is composed of braided fibers with pigments of brown, black, yellow and red. The ratio of these pigments determines hair color. The cuticle is also responsible for whether hair is straight or curly, tough or weak, thick or thin. The cuticle is made mostly from protein and water.
Medulla
Inside the cortex of some hairs is a medullary canal. This canal contains only air and seems to have little or no effect on the properties of a strand of human hair.
HHJ- Ladyno
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