Skin is considered as one of the most important parts of the body as it plays an important role of protecting the body from external harmful germs and diseases. Skin is an organ of the integumentary system made up of multiple layers of tissues that guard muscles and organs in the body. The skin is the largest organ of the human body as it covers the body thus having the largest surface area. The skin is divided into 3 main layers, namely: Epidermis, Dermis, and Subcutaneous tissue. The top layer is epidermis, which is further divided into different layers.
The top layer is the epidermis that has a waterproof function and and serves as a barrier to infection. The epidermis has no blood vessels. The main type of cells which make up the epidermis are keratinocytes, melanocytes and Langerhans cells. The epidermis can be further subdivided into the following strata corneum, lucidum, granulosum, spinosum, basale. The stratum corneum is the outermost layer. It is thin, but rough, protective top layer of dead skin cells, the remainder of the epidermis is made up of cells called keratinocytes as well as melanocytes, which are pigment cells responsible for skin pigmentation. A process called keratinization takes place in the epidermis and is reponsible for keeping water in the body and keeping other harmful chemicals out, making skin a natural barrier to infection.
The dermis has supporting and elastic tissue, nerves, blood vessels, oil glands, sweat glands and hair roots. The types of tissue present in the dermis are collagen, elastic tissue, and reticular fibers. The two layers of the dermis are the papillary and reticular layers. The upper, papillary layer, contains a thin arrangement of collagen fibers. The lower, reticular layer, is thicker and made of thick collagen fibers that are arranged parallel to the surface of the skin. Erector muscles attached between the hair papilla and epidermis can contract, resulting in the hair fibre pulled upright and therefore causing the formation of goose bumps. Papillary ridges make up the lines of the hands and feet, producing individually unique finger prints and foot prints.
The subcutaneous tissue is made up of fat cells between the skin and the deeper muscles. This layer is important as it main function is to ensure the regulation of temperature of the skin itself and the body. The size of this layer varies throughout the body and from person to person.