The skin forms a protective layer against infection, radiation (UV light), heat and mechanical trauma, but also functions to retain moisture and regulate temperature. The skin consists of the epidermis, the outer layer and the dermis.
The top layer, the epidermis, consists of five layers as seen in the image above. The most superficial layer is the statum corneum, followed by lucidum, granulosum, spinosum and the deepest layer, the stratum basale, known as the basal layer. This layer is attached to the papillary layer of the dermis. Melanocytes, responsible for the color of skin and absorption of of UV-B rays, helps to protect skin cells. Merkel cells are in the basal layer and are in contact with sensory nerve endings and associated with the sense of light touch. Langerhans cells are immune cells located in the stratum spinosum.
The deeper layer is the dermis and consists of the papillary layer and the reticular layer. The papillary layer consists of loosely woven connective tissue and the closely associated reticular layer has a criss-crossed collagen pattern which forms a dense connective tissue layer. Small blood vessels are contained in the paillary layer which supply the epidermis, since the epidermis is avascular. Meissner's corpuscles are also located in the papillary layer and they are receptors for touch sensation. The reticular layer also contains Pacinian corpuscles which sense deep pressure. The reticular layer also contains hair folicles, sweat glands, lymph vessels and smooth muscle.
last updated 4/22/15
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