Structure of Friction Skin

Cross-section of Friction Skin

Thick skin (which includes friction skin) has two principle layers:

The Epidermis (E) is stratified (layered), squamous (flat) epithelial tissue 5 layers thick and...

The Dermis is much thicker than the epidermis and consists of two layers - the Papillary layer (DPL) an area of loose connective tissue extending up into the epidermis as dermal pegs (DP) and the deeper reticular layer (DRL).




Stratum corneum - consists of 25-30 layers of stratified (layered) squamous (flattened) dead keratinocytes (skin cells) that are constantly shed.
Stratum lucidum - is present only in thick skin (lips, soles of feet, and palms of hands). Little or no cell detail is visible.
Stratum granulosum - 3-4 layers of cell thick consisting of flattened keratinocytes. At this level the cells are dying.
Stratum spinosum - several layers thick, consisting mostly of keratinocytes. Together with the stratum basale it is sometimes referred to as the Malpighian layer (living layer).
Stratum basale - a single layer of cells in contact with the basement membrane. These cells are mitotically active - they are alive and reproducing - the reason why it is often referred to as the generating layer. Four types of cells are present in this layer:
Keratinocytes (90%) - responsible for waterproofing and toughening the skin
Melanocytes (8%) - synthesize the pigment melanin which absorbs and disperses ultraviolet radiation
Tactile cells - very sparse and function in touch reception
Nonpigmented granular dendrocytes - cells that ingest bacteria and foreign debris.


The primary function of the dermis is to sustain and support the epidermis.
The papillary layer (DPL) is made up of connective tissue with fine elastic fibres. The surface area of this layer is increased by the dermal papillae (DP). These fingerlike formations greatly increase the surface area for the exchange of oxygen, nutrients and waste products between the dermis and the epidermis.



The boundary between the dermis and epidermis is a point of potential weakness where the two tissues may be separated from each other. The fingerlike formations (or interdigitation) also serve to strengthen the epidermis/dermis junction.
As one ages the dermal papillae tend to flatten and may increase in numbers. In this situation, each papilla appears to develop into a group...staying at the same overall size but individually much smaller.



Sweat glands, or eccrine glands, are found over the entire surface of the body except a few small areas. They are most concentrated in the palms and soles of the feet. The eccrine sweat glands in this skin section are well developed, and their ducts (dark staining) can be distinguished from the lighter staining secretory portions.
They are simple coiled tubular glands; they consist of a highly coiled secretory portion deep in the dermis, and a relatively straight duct conducts the secretions toward the surface of the epidermis. Each duct opens in the centre of the ridge "unit" (cristae cutis).
Eccrine sweat contains approximately 99% water and 1% solids. The solids are half inorganic salt (mostly sodium chloride) and organic compounds (amino acids, urea and peptides).


Photos and information came from the following website:
http://www.ridgesandfurrows.homestead.com/friction_skin.html