文档介绍：The constructions and functions of skin皮肤结构和功能
Healthy body depend on health skin.
The skin is a aesthetic（审美） organ.
The skin is a vital organ like heart is.
Outline
Epidermis表皮
Dermis真皮
Subcutaneous tissue皮下组织
Cutaneous appendage皮肤附属器
The functions of skin 皮肤的功能
The skin anatomy(皮肤的解剖)
The skin is the integument(外皮） of body.
It is the largest organ of the body ,making up 16%of body weight, with a surface of m2
The depth of skin is ～4mm.
The epidermis(表皮） is -，the average depth of epidermis is .
The dermis （真皮） is 1-3mm.
In China , the average depth of man is , such as the back of trunk is ，the eyelid is .
The skin anatomy
It’s continuous with the digestive system (lips).腔口部位形成皮肤黏膜的移行区
The skin grooves(皮沟) and skin ridges (皮嵴)
There are three structural layers to the skin: the epidermis（表皮）,the dermis（真皮）and subcutis（皮下组织）
The dermis contains nerve endings, sweat glands （汗腺）and oil glands, hair follicles（毛囊）, and blood vessels（血管）.
The color of skin
The epidermis (表皮)
The epidermis is an epithelium（上皮） comprised of keratinocytes（角质形成细胞） and dendritic cells(langerhans cells朗格汉斯细胞 ,merkel cells麦克尔细胞 ,melanocytes黑素细胞 ).
The main cells of the epidermis are the keratinocytes (角质形成细胞 80%),which synthesise the protein keratin(角蛋白).
stratum basale, 基底层
stratum corneum 角质层
stratum spinosum 棘层
stratum granulosum 颗粒层
stratum lucidum 透明层
The epidermis (表皮)
Stratum basale(基底层)： is a major region of mitotic(分裂)activity. The basal layer is composed of columnar（柱状） cells which are anchored to a basement membrane （基地膜）
Epidermal transit time(表皮通过时间或更替时间):
New keratinocytes slowly migrate up toward the surface of the epidermis. The process needs 28 days.
From stratum basale to stratum granulosum is 14 days, then to stratum corneum and gradually shed is 14 days. Total is 28 days.
Stratum spinosum (棘细胞层)
is composed of 4 to 8 layers of prickle (多角形的） keratinocytes.
Keratinocytes are attached t