Wednesday, January 23

Epidermis - Definition of epidermis

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The epidermis is the outermost of the two layers of skin. Epidermis is composed of five well defined layers, namely strata corneum, lucidum, granulosum, spinosum and germinativum.
In structure it is made up of keratinocytes, melanocytes, Langerhans cells and Merkel cells.

The proliferating basal cells differentiate into keratinocytes for forming a natural barrier against the elements and pathogens and also protect the skin from loss of moisture.

Merkel cells present in it are mechanoreceptors and make the skin sensitive to touch. Langerhans cells have immune function and help in eliminating pathogens.
Human skin color complexion is due to the melanin pigment produced by the melanocytes.

Definition of epidermis

As per Wordnetweb.princeton.edu/perl/webwn the definition is:
"the outer layer of the skin covering the exterior body surface of vertebrates."

Thefreedictionary.com's definition is:
"the outer, protective, nonvascular layer of the skin of vertebrates, covering the dermis."

According to Macmillan Dictionary it is:
"the outer layer of skin on top of the dermis. Hair and feathers grow from the epidermis."

According to Merriam-Webster it is:
"the outer epithelial layer of the external integument of the animal body that is derived from the embryonic epiblast; specifically : the outer nonsensitive and nonvascular layer of the skin of a vertebrate that overlies the dermis."

The definition by Oxford Dictionaries is;
"the surface epithelium of the skin of an animal, overlying the dermis."
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
Image source:
http://en.wikipedia.org/wiki/File:Skinlayers.png
Author: Serephine
License: Public domain

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