Stratum lucidum definition - Function of stratum lucidum layer

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Stratum lucidum is a well defined epidermal layer found under the corneum region of the skin of the palms and soles. Main function of this stratum is to help the skin handle friction and also waterproof it.

It is a thin transitional layer of epidermis found between the 'horny' and 'granular' layers. However in the rest of the body where the skin is thinner, this stratum does not appear differentiated from the granular region.

Stratum lucidum definition according to Merriam-Webster is: "a thin somewhat translucent layer of cells lying superficial to the stratum granulosum and under the corneum especially in thickened parts of the epidermis (as of the palms or the soles of the feet).

1.Epidermal skin showing stratum lucidum

Stratum lucidum is defined as "the layer of epidermis immediately under the corneum in the skin of the palms and soles" by wordnetweb.princeton.edu/perl/webwn

Skin structure showing stratum lucidum

This transparent or translucent layer is composed of three to five tiers of dead keratinocytes. Here these cells do not have distinct boundaries and are flattened. These dead keratinocytes contain a clear intermediate form of keratin called eleidin. The presence of melanosomes may determine the level of its darkness. They are surrounded by fatty substance, probably as the result of the exocytosis of lamellar bodies in the previous tiers. The presence of the oily substance is responsible for the waterproofing function. This barrier function makes the inner regions fairly impermeable to water from outside as well as preventing loss of water from inner cells. Another probable function of this tier is in reduction of friction.

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Reference:
1.Harding, C. R. (2004), The st. corneum: structure and function in health and disease. Dermatologic Therapy, 17: 6–15. doi: 10.1111/j.1396-0296.2004.04S1001.x
2.Zirra AM. The functional significance of the skin's st. lcidum. Morphol Embryol (Bucur). 1976 Jan-Mar;22(1):9-12.
1.Image source:
http://en.wikipedia.org/wiki/File:Skinlayers.png
Author: Serephine
License: Public domain
2.Image source:
http://en.wikipedia.org/wiki/File:Epidermal_layers.png
Author: Mikael Häggström, based on work by Wbensmith
License: CC BY-SA 3.0
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