Parts of the skin

The skin is divided into two main layers, the epidermis at the surface, and the dermis beneath.  Below the dermis is another layer, not strictly part of the skin, called the hypodermis. The epidermis is made up of stratified epithelium.  The bottom-most layer of cells, the Malpighian layer, contains variable amounts of black pigments melanin which protects the body from the harmful effects of ultraviolet rays from the sun. The cells of the Malpighian layer divide repeatedly in a plane horizontal to the surface of the body.  As new cells are formed, the older ones get pushed outwards towards the surface, flattening as they do so.  After a time, the cytoplasm becomes converted into scales of Keratin, giving rise to the Keratinised layer at the surface of the epidermis.  The keratinized layer protects the skin from damage and makes it waterproof. Oil is secreted on to the surface of the epidermis by sebaceous glands makes the hair supple and enhances the skin’s waterproofing properties. The roots of the hair are embedded in the dermis or hypodermis.  Running from the side of each hair follicle to the base of the epidermis is erector pili muscle.  When this muscle contracts, the hair is pulled into a more vertical position. In this position hair trap, a layer of air around the skin thereby insulating the skin from heat loss. The dermis contains sweat glands that secrete a salty solution, sweat.  The sweat passes down the sweat ducts to the surface of the epidermis, and its subsequent evaporation cools the skin and blood flowing through it. The hypodermis contains a variable amount of fat (subcutaneous fat) which insulates and prevents heat loss from the body. Please find free downloadable notes, exams and marking guides of agriculture, biology, Physics, chemistry etc.  from digitalteachers.co.ug website. Dr. Bbosa Science