Many people do not realize how complex the skin actually is. It has many different structures each serving a different and equally important purpose. The skin is divided up into several layers. From top to bottom there is the epidermis, dermis, and hypodermis. The epidermis serves to protect the skin with its keratinized cells. The dermis allows the skin to stretch with its dense connective tissue, and the hypodermis anchors the skin to the underlying tissue. Within the epidermis there are 5 layers. The bottom layer is the stratum basale, which is where cells undergo mitosis. The next layer is the stratum spinosum, where cells attach together using the desmozomes. This is followed by the granulosum layer, where keratin first gets deposited into the cell. Next is the Lusidum layer, where the cell is completely filled with keratin. By the time the cell gets to the final layer, the stratum corneum, the cell is dead, and can protect the body. As you can see from the picture below, the skin has several different organisms within the skin. The sebaceous glands produce oil, or sebum, to help lubricate the skin to keep bacteria from forming on the skin. Unfortunately this sebum is also responsible for the formation of pimples.
Skin is imperative in the bodies struggle to maintain homeostasis. One of the skins main tasks is to protect deeper tissue from various types of damage. The skins ability to stretch allows it not to rip when we bend our bones, thus protecting the body from mechanical damage. This is allowed due to the dense connective tissue found in the Dermis. Dense connective tissue is also found by ligaments and tendons, which is why it must be able to withstand stretching and pulling. The skin also protects from chemical damage and bacterial damage, which can cause disease. It does this because the cells located in the corneum are severely keratinzed. This tough barrier becomes water resistant, preventing chemicals or bacteria from entering and exiting the body. Vitamin D is also synthesized in the skin, a vitamin important for the absorption and metabolism of calcium ions. Vitamin D is important for bone development.