皮膚的構造與功能皮膚的構造與功能

高榮皮膚科主治醫師高榮皮膚科主治醫師陳雅惠陳雅惠

Look at your skinLook at your skin

More than a coveringMore than a covering A vital organ, complex structureA vital organ, complex structure Develop from the same tissues as the Develop from the same tissues as the

brainbrain

Skin factsSkin facts

Surface area: about 2500 cm² in a Surface area: about 2500 cm² in a newborn baby, 18000 cm² in an adult.newborn baby, 18000 cm² in an adult.

About 6-16% of body weight: average 3 About 6-16% of body weight: average 3 kg in a woman, perhaps 5 kg in a man. kg in a woman, perhaps 5 kg in a man.

thickness: varies on sites. thinnest on thickness: varies on sites. thinnest on the eyelids and thickest on the palms the eyelids and thickest on the palms and the soles.and the soles.

Three layers: Three layers: epidermis, dermis, subcutaneous fatepidermis, dermis, subcutaneous fat

EpidermisEpidermis Thickness: 35-50Thickness: 35-50m, only 20 m, only 20 m m

around eye, thicker on the palm and around eye, thicker on the palm and sole (mm) sole (mm)

oxygen and nutrients from the dermisoxygen and nutrients from the dermis TranslucentTranslucent Basement membraneBasement membrane Rete ridgesRete ridges

Epidermis-2Epidermis-2

All keratinocytes originate from basal layerAll keratinocytes originate from basal layer Move upward,change shape and loss Move upward,change shape and loss

nucleus, producenucleus, produce

skin protein (keratin)skin protein (keratin)

and fat (sphigolipid,and fat (sphigolipid,

ceramide)ceramide) Corneocytes: deadCorneocytes: dead Resist to injuryResist to injury

keep waterkeep water

Epidermis-2Epidermis-2

Desquamation (squames)Desquamation (squames) Renew cycle: about 30 daysRenew cycle: about 30 days Psoriasis: 4-7 times fasterPsoriasis: 4-7 times faster Speed up: sunburn, peelSpeed up: sunburn, peel agingaging

Epidermis-3Epidermis-3

A model of “bricks and mortar”A model of “bricks and mortar” Corneocytes, desmosomes, natural fatCorneocytes, desmosomes, natural fat up to 15% of the stratum corneum consists up to 15% of the stratum corneum consists

of water. of water. TEWL (transepidermal water loss)TEWL (transepidermal water loss)

DermisDermis 3000 3000 m thick, keep resilience and supplem thick, keep resilience and supple Contain blood vessels, nerves, hair roots anContain blood vessels, nerves, hair roots an

d sweat glandsd sweat glands Fibroblasts make collagen and elastinFibroblasts make collagen and elastin Ground substance: glycoprotein (hyaluronic Ground substance: glycoprotein (hyaluronic

acid, chrondroitin sulfate), maintain wateracid, chrondroitin sulfate), maintain water

Dermis-2Dermis-2

Collagen: 75%Collagen: 75%

Elastic fibers: Elastin, 5%Elastic fibers: Elastin, 5%

Stretch marksStretch marks

Wound repairWound repair– Across lines, deep, largeAcross lines, deep, large

– Granulation tissueGranulation tissue

– Hypertrophic scarHypertrophic scar

– KeloidKeloid

Subcutaneous fat layerSubcutaneous fat layer

Adipocytes, larger vessels and nervesAdipocytes, larger vessels and nerves Depth differs from site and individualDepth differs from site and individual Cushing, conserve body heatCushing, conserve body heat store fat: women (buttocks and thighs), store fat: women (buttocks and thighs),

men (abdominal wall)men (abdominal wall) cellulitecellulite

Sebaceous glandsSebaceous glands Part of hair folliclesPart of hair follicles in every part except palm and solein every part except palm and sole Sebum: pH= 4.2-5.6, protect skin and lubricate hair Sebum: pH= 4.2-5.6, protect skin and lubricate hair

shaftshaft Mixture of sebum and sweat:Mixture of sebum and sweat: natural oil-in-water emulsion,natural oil-in-water emulsion, kill some fungikill some fungi Influence by male hormoneInfluence by male hormone most sensitive at pubertymost sensitive at puberty on face and trunkon face and trunk

Eccrine glandsEccrine glands

Empty directly on to the skinEmpty directly on to the skin in every part except lips and glans penisin every part except lips and glans penis Produce sweat: mixture of water and saltsProduce sweat: mixture of water and salts Regulate theRegulate the

body temperaturebody temperature Remove wasteRemove waste

Apocrine glandsApocrine glands

In axillary and genital area, breastIn axillary and genital area, breast Decapitation secretionDecapitation secretion Dependent on sex hormoneDependent on sex hormone Germs grow in moist areaGerms grow in moist area

produce body odorproduce body odor

HairsHairs

Vellus hairs: most skin, attached to tiny Vellus hairs: most skin, attached to tiny muscles in the dermis, “goose bumps”muscles in the dermis, “goose bumps”

Terminal hairs: scalp, eyelids, eyebrows, Terminal hairs: scalp, eyelids, eyebrows, Beard, chest, arm and leg: due to male Beard, chest, arm and leg: due to male

hormonehormone Cuticle, cortex, medullaCuticle, cortex, medulla

Blood vesselsBlood vessels Supply the skin and appendagesSupply the skin and appendages Regulate body temperatureRegulate body temperature Sympathetic nerve make it constriction; Sympathetic nerve make it constriction;

parasym. nerve, dilatation.parasym. nerve, dilatation.

NervesNerves

Autonomic nerves: vessels, sweat glands, Autonomic nerves: vessels, sweat glands, smooth musclessmooth muscles

Sensory nervesSensory nerves Subepidermal plexusSubepidermal plexus Merckel plexusMerckel plexus

Functions of the epidermisFunctions of the epidermis

protecting the body from the protecting the body from the environment, particularly the sun environment, particularly the sun

preventing excessive water loss from preventing excessive water loss from the body the body

protecting the body from infection. protecting the body from infection.

Functions of the epidermis-1Functions of the epidermis-1

ultraviolet radiation create free radicals ultraviolet radiation create free radicals protecting the nuclei of the cells in the protecting the nuclei of the cells in the

epidermis and the collagen of the epidermis and the collagen of the dermisdermis– Part is reflected by the stratum corneum at Part is reflected by the stratum corneum at

the skin surfacethe skin surface– part is absorbed by the melanin in the part is absorbed by the melanin in the

epidermal cellsepidermal cells– some is scattered within the skinsome is scattered within the skin

Functions of the epidermis-2Functions of the epidermis-2

Water: 70-75% of the weight of the basal layer, Water: 70-75% of the weight of the basal layer, but only 10-15% of the stratum corneum.but only 10-15% of the stratum corneum.

If below 10%, it becomes dry, less flexible and If below 10%, it becomes dry, less flexible and prone to damage, breakdown and infection.prone to damage, breakdown and infection.

The epidermis as a whole is about 35The epidermis as a whole is about 35m thick m thick when dry, swell to 48 when dry, swell to 48 m on full hydration.m on full hydration.

Functions of the epidermis-3Functions of the epidermis-3

Hydration components of Stratum componentHydration components of Stratum component1. Keratin1. Keratin2. a cornified envelope of corneocytes2. a cornified envelope of corneocytes3. 3. LipidsLipids

– Linoleic acid (diet), ceramidesLinoleic acid (diet), ceramides

44. natural moisturising factors (NMF). natural moisturising factors (NMF)– Amino acids (40%), pyrrolidone carboxylic acid (12Amino acids (40%), pyrrolidone carboxylic acid (12

%), lactic acid (12%), urea (8%), salts (18%), unideti%), lactic acid (12%), urea (8%), salts (18%), unidetified compounds (10%)fied compounds (10%)

5. desmosomes5. desmosomes6. enzymes6. enzymes

Functions of the epidermis-4Functions of the epidermis-4

Three level against invasion by microorganThree level against invasion by microorganism ism – Natural layer of oil-in-water emulsion on skinNatural layer of oil-in-water emulsion on skin– Stratum corneumStratum corneum– White blood cells in skinWhite blood cells in skin

Defense concerns chemicalsDefense concerns chemicals– Langerhans cellsLangerhans cells

semipermeablesemipermeable

Functions of the dermisFunctions of the dermis protection to the body from bumps and knocksprotection to the body from bumps and knocks provide oxygen and nutrientsprovide oxygen and nutrients remove waste products of metabolism from the remove waste products of metabolism from the

epidermis, which are also carried away in the bloodepidermis, which are also carried away in the blood provide shape and form to the body, by holding all its provide shape and form to the body, by holding all its

structures togetherstructures together contributing to skin color, particularly in people with little contributing to skin color, particularly in people with little

melanin in the epidermismelanin in the epidermisOrgans in the dermis have special functions of their own:Organs in the dermis have special functions of their own: regulation of body temperature through control of blood regulation of body temperature through control of blood

flow and sweating flow and sweating skin sensations of touch, pain, heat and cold skin sensations of touch, pain, heat and cold