The skin contains 3 layers: epidermis, dermis, and hypodermis. First of all each layer has a specific function that allows the integument system to work properly together. The epidermis is the outermost layer of the skin which is the first line of defense for outside invaders. Within the epidermis there is 5 layers that work among each other to protect the body internally. The layers from the most outer to inner are the stratum corneum, stratum lucidum, stratum granulosm, stratum spinosum, and the deepest layer the stratum basale. Starting from the deepest layer, stratum basale, which contains keratinocytes. These are cells that produce keratin a hardening protein and also in this layer are melanocytes which are cells that make melanin that is used to determine color pigment. From this layer the keratinocytes travel to the stratum spinosum. The keratinocytes are connected through desmosomes which makes the cells to apperar “spiny” and this is where keratinization occurs. The cells become cemented creating a tough elastic barrier which contains collegen. The next layer, sratum granulosm this is where the keratinocytes become waxy and grain-like to begin to dessicate the skin. This allows for the skin to have a barrier and keep from liquids from getting through. Each layer aids in making the skin more resistant to water. The stratum lucidum is composed of layers of dead, flattened keratinocytes which are usually only found in soles of the feet and hands because it is such a thick layer. The final outer layer the stratum corneum is the final step of keratinization where dead cells shed and the entire process begins again. This layer is composed of dead cells which is the barrier used to protect underlying tissue from infection, dehydration, chemicals, and mechanical stress. The next layer of the skin is the dermis which contains only 2 layers, the papillary and reticular. The papillary layer contains dermal papillae which are nipple-like extensions that reach into the epidermis which creates more space for nerves and blood vessels that are found in the dermis. The innermost layer of the dermis is the reticular which contains the accessory organs which include hair follicles, nerve receptors, blood vessels, sweat and oil glands. Phagocytes are also found here and act to prevent bacteria that happened to get through the epidermis layer. The dermis has a rich nerve supply and have specialized receptor organs that send messages to the central nervous system. The dermis also plays a big role in maintaining body temperature. When temperature is high the capillaries expand which cause skin to appear red and warm. When the environment is cold the body heat must be conserved so the capillaries allow internal body temperatures to stay high. The final layer of the skin is the hypodermis or subcutaneous layer. This is the deepest layer of the skin where the skin is anchored to underlying organs. This layer serves as a shock absorber because of the fatty tissue it contains. It also insulates deeper tissues from extreme temperature changes. Homeostasis is maintained through the entire organ system by working as a unit to keep its proper form and function.