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Hair Structure - Hair Shaft Layers of the Hair It consists of: 1. Cuticle 2. Cortex 3. Medulla Medulla Cortex Cuticle 1.The Cuticle • The cuticle is the outside of the hair shaft. • It is made up of overlapping, transparent scales which protect the cortex. • It is made of Hard Keratin & is usually 7 - 10 layers thick. • The cuticle determines porosity of hair Condition of the Hair A perfect hair, its cuticle intact, taken from a newborn baby Damaged cuticle Condition of the Hair Heated appliances soften the keratin of the hair. If they are too hot, they can actually cause the water in the hair to boil, and tiny bubbles of steam then form inside the softened hair shaft. The hair is thereby weakened, and may break altogether. 2.The Cortex • The Cortex is the largest and most important layer and is made of hard keratin • Approximately 80% of hairs total mass • Determines the texture and elasticity of the hair • Peptide, sulphur, hydrogen and ionic bonds found here – these bonds allow us to temporarily or permanently change the shape of the hair. • It is a complicated structure of parallel twisted fibre; the appearance is similar to a rope. • These fibres of hard keratin are formed from amino acids which are joined end to end by Peptide Bonds. • Strings of Polypeptide chains are linked together by a cross bond called a Di- Sulphide Bond • All chemical and physical changes take place in the cortex because this is where all the bonds are found. • The size of the cortex determines the texture of the hair shaft. • The elasticity of this layer enables the hair to be physically re-arranged • Melanin hair’s natural colour is in this layer. 3. Medulla • The medulla is found in the center of the hair shaft. • Not every hair has a medulla, it may be continuous or broken along the length of the hair shaft. • The medulla is made of Soft Keratin and sometimes it may contain melanin. The formation of the hair follicle • The follicle is a pocket in the skin that the hair grows from. • The follicle grows through the epidermis and into the dermis. • There are billions of follicles all over the human body and thousands over the scalp. Structure of the follicle • There are three main parts of the follicle: • 1. Papilla • 2. The Germinal Matrix • 3. The Hair Bulb Papilla • The papilla is found at the bottom of the follicle in the dermis. It is shaped like the skin is pushed up into the bottom of the follicle. • This is where the blood capillaries pass nutrients (food) and oxygen into the cells of the germinal matrix. Germinal Matrix • The germinal matrix is inside the follicle, above the papilla, it is full of cells that are constantly dividing. • These cells join together and eventually become the hairshaft Hair bulb • The hair bulb is the name of the lower part of the follicle. It is shaped like a light bulb. • This is where the new cells start the process of keratinization There are two other parts of the follicle: • 1. The Sebaceous gland is attached to the side of the follicle and has an opening into the follicle. • It is the oil gland that secretes sebum into the follicle. From the follicle the sebum will eventually coat the surface of the hairshaft and the skin. The Arrector-Pili-Muscle • Is also attached to the side of the follicle. • It is described as an involuntary muscle. • When you get cold or frightened it will contract and pull the follicle upright. This makes the skin at the mouth of the follicle bunch up causing what we call ‘goose pimples’.