What is skin(8)? dermis




The skin has three layers. They are epidermis, dermis and subcutaneous tissues

.

Dermis
It consists of connective tissue and provides elasticity of the skin. 
Its thickness depends on the body part. The average is around 1-4mm. eyelid is only 0.3 mm. back , palms and soles may be more than 3mm.

Structure of dermis
1. Fibers
Elastic fiber, collagen, reticulum fibers
2. Basic material
Glycoproteins, acid mucopolysaccharides, neutral mucopolysaccharides, etc.
3. Cell
Fibroblast, mast cell, macrophage, etc.
4. Organ
blood capillaries, nerves, glands, and hairs

The structure could be divided into 2 types. They are papillary dermis and reticular dermis.
papillary dermis
l   Close to the epidermis, the thickness is 1/5 of dermis thickness
l   Consist of low density connective tissue
l   collagen fibers and elastic fiber with many capillary, is called subpapilary plexus
the low density is easy for the phagocytes and immunocyte to translate

reticular dermis.
l   The lower layer of dermis, the thickness dominate 4/5 of the total thickness. Highr density connective tissue place in random arrangement
l   the interface of dermis and subcutis distribute many blood vessels such that it is called cutaneous plexus
l   adipocyte and  collagen fibers and elastic fibers
l   the direction of fibers cause the line of skin surface such as the sides of joints. The lines also are called lines of cleavage and tension lines.

Function of dermis
l   Provide metabolism
Because dermis has many blood vessels, the metabolism substances of epidermis are all from here.
The lymph will translate from circulatory system

l   Provide elastic properties
70% is collagn, in charge of the stability of skin, prevent to tear out
elastic fibers distribute in the gap of collagen fibers. Provide the elastic properties.
Among cells and fibers, fill with proteoglycans to connect the structure.

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