Skin anatomy and conditions
Facts about the skin
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:
- subcutis, or fat layer
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 that contain fibrous proteins, or 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, or 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.
The dermis is the middle layer of the skin. It contains the following:
- blood vessels
- lymph vessels
- hair follicles
- sweat glands
- collagen bundles
The dermis is held together by a protein called collagen, made by fibroblasts. This layer also contains pain and touch receptors.
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."
A physician may ask you to describe your child's dermatological condition and its location. Here are some of the most common terms that may help you in providing a more accurate description:
- atrophic: thin, wrinkled
- blister: a fluid-filled bump
- crust/scab: formation of dried blood, pus or other skin fluid over a break in the skin
- cyst: a 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: a solid, raised bump
- raised bumps: bumps that stick out above the skin's surface
- patch: a 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