The skin is the body’s largest organ. The integumentary system consists of the skin and any accessory structures, such as hair follicles, exocrine glands, nails or nerves. There are three main layers of the skin: the top most superficial is the epidermis, the middle is the dermis, and the lowest part is the hypodermis. The epidermis creates a protective, waterproof barrier for human bodies and also is responsible for creating skin tone as melanin-producing melanocytes are located in this layer. The epidermis can also be broken down into five layers (from top to bottom): stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. These can be remembered in order via the mnemonic: “come let’s go sun bathe.” The dermis contains hair follicles, sweat glands, and connective tissue. The dermis is made of two layers: the papillary layer and the reticular layer. This is also the outermost layer to be vascularized. The hypodermis is deeper subcutaneous tissue and is made of mostly fat and connective tissue.
The skin’s main function is to protect the body from harm. This includes protection from exposure to bacteria or other harms in the environment, and protection from loss of water and subsequent dehydration. The skin also helps maintain homeostatic temperature through the sweating mechanism. Nerves in the skin detect stimuli in the environment as they sense temperature, pain, and pressure. Therefore, injuries to the skin can often result in imbalances in homeostatic processes and major complications if not addressed quickly. Serious injuries to the skin, such as large or deep burns, can even result in death.
