SkinStruFunction
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Transcript SkinStruFunction
皮膚的構造與功能
高榮皮膚科主治醫師
陳雅惠
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: 35-50m, 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
Subcutaneous fat layer
Adipocytes, larger vessels and nerves
Depth differs from site and individual
Cushing, conserve body heat
store fat: women (buttocks and thighs),
men (abdominal wall)
cellulite
Sebaceous glands
Part of hair follicles
in every part except palm and sole
Sebum: pH= 4.2-5.6, protect skin and lubricate
hair shaft
Mixture of sebum and sweat:
natural oil-in-water emulsion,
kill some fungi
Influence by male hormone
most sensitive at puberty
on face and trunk
Eccrine glands
Empty directly on to the skin
in every part except lips and glans penis
Produce sweat: mixture of water and salts
Regulate the
body temperature
Remove waste
Apocrine glands
In axillary and genital area, breast
Decapitation secretion
Dependent on sex hormone
Germs grow in moist area
produce body odor
Hairs
Vellus hairs: most skin, attached to tiny
muscles in the dermis, “goose bumps”
Terminal hairs: scalp, eyelids, eyebrows,
Beard, chest, arm and leg: due to male
hormone
Cuticle, cortex, medulla
Blood vessels
Supply the skin and appendages
Regulate body temperature
Sympathetic nerve make it constriction;
parasym. nerve, dilatation.
Nerves
Autonomic nerves: vessels, sweat glands,
smooth muscles
Sensory nerves
Subepidermal plexus
Merckel plexus
Functions of the epidermis
protecting
the
body
from
the
environment, particularly the sun
preventing excessive water loss from
the body
protecting the body from infection.
Functions of the epidermis-1
ultraviolet radiation create free radicals
protecting the nuclei of the cells in the
epidermis and the collagen of the
dermis
– Part is reflected by the stratum corneum at
the skin surface
– part is absorbed by the melanin in the
epidermal cells
– some is scattered within the skin
Functions of the epidermis-2
Water: 70-75% of the weight of the basal layer,
but only 10-15% of the stratum corneum.
If below 10%, it becomes dry, less flexible and
prone to damage, breakdown and infection.
The epidermis as a whole is about 35m thick
when dry, swell to 48 m on full hydration.
Functions of the epidermis-3
Hydration components of Stratum component
1. Keratin
2. a cornified envelope of corneocytes
3. Lipids
– Linoleic acid (diet), ceramides
4. natural moisturising factors (NMF)
– Amino acids (40%), pyrrolidone carboxylic acid
(12%), lactic acid (12%), urea (8%), salts (18%),
unidetified compounds (10%)
5. desmosomes
6. enzymes
Functions of the epidermis-4
Three level against invasion by
microorganism
– Natural layer of oil-in-water emulsion on skin
– Stratum corneum
– White blood cells in skin
Defense concerns chemicals
– Langerhans cells
semipermeable
Functions of the dermis
protection to the body from bumps and knocks
provide oxygen and nutrients
remove waste products of metabolism from the
epidermis, which are also carried away in the blood
provide shape and form to the body, by holding all its
structures together
contributing to skin color, particularly in people with little
melanin in the epidermis
Organs in the dermis have special functions of their own:
regulation of body temperature through control of blood
flow and sweating
skin sensations of touch, pain, heat and cold