300 Longwood Avenue Boston, MA 02115 (617) 355-6000 My Child Has: Skin: Anatomy and Conditions Programs related to this topic Dermatology Program   Facts about the skin click to enlarge The skin is the body's largest organ, covering the entire body. In addition to serving as a protective shield against heat, light, injury, and infection, the skin also: regulates body temperature stores water and fat is a sensory organ prevents water loss prevents entry of bacteria Throughout the body, the skin's characteristics vary (i.e., thickness, color, texture). For instance, the head contains more hair follicles than anywhere else, while the soles of the feet contain none. In addition, the soles of the feet and the palms of the hands have much thicker layers. Layers of the skin The skin is made up of the following layers, with each layer performing specific functions: epidermis dermis fat layer Epidermis The epidermis is the thin outer layer of the skin, which consists of the following three parts: stratum corneum (horny layer) This layer consists of fully mature keratinocytes which contain fibrous proteins (keratins). The outermost layer is continuously shed. The stratum corneum prevents the entry of most foreign substances as well as the loss of fluid from the body. keratinocytes (squamous cells) This layer, just beneath the stratum corneum, contains living keratinocytes (squamous cells), which mature and form the stratum corneum. basal layer The basal layer is the deepest layer of the epidermis, containing basal cells. Basal cells continually divide to form new keratinocytes, replacing the old ones that are shed from the skin's surface. The epidermis also contains melanocytes, which are cells that produce melanin, a skin pigment. Dermis The dermis is the middle layer of the skin. It contains the following: blood vessels lymph vessels hair follicles sweat glands collagen bundles fibroblasts nerves The dermis is held together by a protein called collagen, made by fibroblasts. This layer also contains pain and touch receptors. Subcutis The subcutis is the deepest layer of skin. Consisting of a network of collagen and fat cells, the subcutis helps conserve the body's heat and protects the body from injury by acting as a "shock absorber." Skin Conditions A physician may ask you to describe your child's dermatological condition and its location. Here are some of the more common terms that may help you in providing a more accurate description: atrophic: thin, wrinkled blister: fluid-filled bump crust/scab: formation of dried blood, pus, or other skin fluid over a break in the skin cyst: deeply seated lesion that contains material excoriation: a scratch hives/wheals: pink or white swelling of the skin lichenification: skin that has thickened macule: a flat discolored spot nodule/papule: solid, raised bump raised bumps: bumps that stick out above the skin's surface patch: flat, discolored spot pustule (pimple): inflamed lesions that appear to contain pus scales: dead skin cells that form flakes scar: fibrous tissue that has formed after a skin injury The information on this website should not be taken as medical advice, which can only be given to you by your personal health care professional. Copyright © Children's Hospital Boston. All rights reserved.