Epidermis (skin)

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Cross-section of all skin layers
Optical Coherence Tomography tomogram of fingertip, depicting stratum corneum (~500µm thick) with stratum disjunctum on top and stratum lucidum (connection to stratum spinosum) in the middle. At the bottom superficial parts of the dermis. Sweatducts are clearly visible.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]


Epidermis is the outermost layer of the skin. It forms the waterproof, protective wrap over the body's surface and is made up of stratified squamous epithelium with an underlying basal lamina.

Components

The epidermis contains no blood vessels, and is nourished by diffusion from the dermis. The main type of cells which make up the epidermis are keratinocytes, melanocytes, Langerhans cells and Merkels cells.

Layers

The epidermis is divided into several layers where cells are formed through mitosis at the innermost layers. They move up the strata changing shape and composition as they differentiate and become filled with keratin. They eventually reach the top layer called stratum corneum and become sloughed off, or desquamated. This process is called keratinization and takes place within weeks. The outermost layer of epidermis consists of 25 to 30 layers of dead cells.

Sublayers

Epidermis is divided into the following 5 sublayers or strata, listed from the superficial to deep:

Mnemonics used for remembering the layers of the skin (using "stratum basale" instead of "stratum germinativum"):

  • "Corn Lovers Grow Several Bales" (from superficial to deep)
  • "Before Signing, Get Legal Counsel" (from deep to superficial)

Additional images

External links

  • Histology at Boston University 08422loa - "Integument: thick skin"


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