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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