Hair
The function of hair is to trap a layer of still air over the surface of the skin, so providing the body with some insulation.
Hair is formed by, and grows through structures called hair follicles. These are tubes lined with epithelial cells that have their bases in the dermis or subcutaneous tissue and lead to the surface of the skin.
All hair follicles have sebaceous glands connected to them, which secrete sebum - an oily substance that lubricates hair and skin and provides some protection against bacteria.
Hair is constructed by the multiplication of cells in the root at the base of the follicle. As these cells are pushed upwards and away from their source of nutrition, they die and are converted into a protein called keratin.
