皮肤的构造与功能课件.ppt

皮肤 结构与功效
Look at your skin
More than a covering
A vital organ, complex structure
Develop from the same tissues as the brain
Skin facts
Surface area: about 2500 cm² in a newborn baby, 18000 cm² in an adult.
About 6-16% of body weight: average 3 kg in a woman, perhaps 5 kg in a man.
thickness: varies on sites. thinnest on the eyelids and thickest on the palms and the soles.
Three layers: epidermis, dermis, subcutaneous fat
Epidermis
Thickness: 35-50m, only 20 m around eye, thicker on the palm and sole (mm)
oxygen and nutrients from the dermis
Translucent
Basement membrane
Rete ridges
Epidermis-2
All keratinocytes originate from basal layer
Move upward,change shape and loss nucleus, produce
skin protein (keratin)
and fat (sphigolipid,
ceramide)
Corneocytes: dead
Resist to injury
keep water
Epidermis-2
Desquamation (squames)
Renew cycle: about 30 days
Psoriasis: 4-7 times faster
Speed up: sunburn, peel
aging
Epidermis-3
A model of “bricks and mortar”
Corneocytes, desmosomes, natural fat
up to 15% of the stratum corneum consists of water.
TEWL (transepidermal water loss)
Dermis
3000 m thick, keep resilience and supple
Contain blood vessels, nerves, hair roots and sweat glands
Fibroblasts make collagen and elastin
Ground substance: glycoprotein (hyaluronic acid, chrondroitin sulfate), maintain water
Dermis-2
Collagen: 75%
Elastic fibers: Elastin, 5%
Stretch marks
Wound repair
Across lines, deep, large
Granulation tissue
Hypertrophic scar
Keloid