The skin is the human body’s largest organ, with a range of functions that support survival. The skin has three layers, the epidermis, dermis, and subcutaneous layer. Each layer performs specific tasks.
The epidermis is seen on the surface of the skin. It contains 5 layers
– Stratum Corneum (Horny Layer): It is the top layer of the epidermis. Cells here are flat and scale-like (squamous) in shape. These cells are dead, contain a lot of keratin and are arranged in overlapping layers that impart a tough and waterproof character to the skin’s surface.
– Stratum Lucidum (Transparent Layer): It is an important layer of the skin, as it provides several types of protection. Due to the thick nature of the stratum lucidum, the effects of friction are reduced, particularly in areas prone to these effects, such as the palms of the hands or the soles of the feet.
– Stratum Granulosum (Granular Layer): In this layer, keratinocytes are now called granular cells, and contain keratohyalin and lamellar granules which secrete sheets of fatty substances. These are deposited into the spaces between the cells of the stratum granulosum, forming a kind of waterproof sealant, which creates the barrier protecting the lower layers of skin.
– Stratum Spinosum (Malpighian Layer): It is also called the spinous or prickle cell layer because of the presence of cells with spiny arms diverging outward and interconnecting with other prickle cells. The stratum spinosum also contains keratinocytes and Langerhans cells. Its main function is to protect against foreign materials, and to produce and retain layers of lipids that prevent moisture loss from the skin.
– Stratum Basale: This layer is The deepest layer of the epidermis. The basal cells lie directly on the basal membrane, which forms a well-defined border between the dermis and epidermis. The basal cells act as mother cells, ensuring continuous regeneration of the skin by cell division (proliferation). The daughter cells are slowly pushed by the actively dividing cells into the outer lying layers where they go through various stages of development. Also found in the basal layer are the melanocytes, which are the pigment-producing cells.
The dermis consists mostly of connective tissue and is much thicker than the epidermis. It is made up of a connective tissue framework in which are embedded blood vessels, lymph vessels, nerves, several types of glands, hair and a whole variety of cells. The connective tissue of the dermis is made up predominantly of a protein called collagen. Presently, this protein is being popularly used for the treatment of a variety of skin problems like wrinkles and scars. For information about skin disorders go to our skin disorders section. Elastin or elastic fibres are the other type of protein fibres in the dermis.
The dermis also contains a complex system of bleed and lymph vessels and a highly complicated nervous system. The nerves receive and pass on an endless stream of valuable information to the body. Any type of skin massage is thought to facilitate the drainage of lymph glands and also to enhance the circulation of blood. Similarly; it has been suggested that massages soothe the nerves in the skin.
When the skin is exposed to sunlight, modified cholesterol in the dermis produces vitamin D, which helps the body to absorb calcium for healthy bones.
The innermost layer of the skin is the layer of subcutaneous fat that helps insulate the body from heat and cold, provides protective padding, and serves as an energy storage area. The fat is contained in living cells, called fat cells, held together by fibrous tissue. The fat layer varies in thickness, from a fraction of an inch on the eyelids to several inches on the abdomen and buttocks in some people.