Epidermis (skin)

All you want to know about Epidermis (skin)

The epidermis is the outermost layer of the skin[1], composed of terminally differentiated stratified squamous epithelium,[2], acting as the body's major barrier against an inhospitable environment.[3]

Contents

Cellular components

The epidermis is avascular, nourished by diffusion from the dermis, and composed for four cell types: keratinocytes, melanocytes, Langerhans cells, and the Merkels cell.[1] Keratinocytes are the major constituent, constituting 95% of the epidermis. [2]

Layers

The epidermis is composed of 4-5 layers depending on the region of skin being considered. Those layers in descending order are the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale.[3] The term Malpighian layer refers to both the basal and spinosum layers.[2]

Cellular kinetics

The stratified squamous epithelium is maintained by cell division within the basal layer. Differentiating cells slowly displace outwards through the stratum spinosum to the stratum corneum, where anucleate corneal cells are continually shed from the surface (desquamation). In normal skin the rate of production equals the rate of loss[2], taking about two weeks for a cell to migrate from the basal cell layer to the top of the granular cell layer, and an additional two weeks to cross the stratum corneum.[3]

Additional images

Epidermis and dermis of human skin

Section of epidermis

Optical coherence tomography of fingertip

Cross-section of all skin layers

References

  1. ^ a b James, William; Berger, Timothy; Elston, Dirk (2005) Andrews' Diseases of the Skin: Clinical Dermatology (10th ed.). Saunders. Page 2-3. ISBN 0721629210.
  2. ^ a b c d McGrath, J.A.; Eady, R.A.; Pope, F.M. (2004). Rook's Textbook of Dermatology (Seventh Edition). Blackwell Publishing. Pages 3.1-3.6. ISBN 9780632064298.
  3. ^ a b c Marks, James G; Miller, Jeffery (2006). Lookingbill and Marks' Principles of Dermatology (4th ed.). Elsevier Inc. Pg 1-7. ISBN 1-4160-3185-5.
v • d • e
Integumentary system
Skin
Epidermis
Basement membrane zone
Adnexa
Glands
Shaft
Muscle
Matrix · Lunula · Nail plate · Nail bed · Eponychium · Paronychium · Hyponychium
Retrieved from "http://en.wikipedia.org/wiki/Epidermis_(skin)"

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