|
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 (thickness, color, texture)
vary. 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 are much thicker. The skin is made up
of the following layers, with each layer performing specific functions:
- epidermis
- dermis
- subcutaneous fat layer
| epidermis |
The epidermis is the
thin outer layer of the skin and consists of 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, forming new keratinocytes
that replace the cells that are shed from the skin's surface.
The epidermis also contains melanocytes, which are cells that produce
melanin (skin pigment).
|
| dermis |
The dermis is the middle layer of the skin. The dermis 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. The subcutis, consisting of a network
of collagen and fat cells, helps conserve the body's heat and protects
the body from injury by acting as a shock absorber. |
|
