Discovery Channel

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Look at your skin

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

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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.

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Three layers epidermis, dermis, subcutaneous fat
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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

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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

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Epidermis-2

• Desquamation (squames)
• Renew cycle about 30 days
• Psoriasis 4-7 times faster
• Speed up sunburn, peel
• aging

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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)

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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

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Dermis-2

• Collagen 75
• Elastic fibers Elastin, 5
• Stretch marks
• Wound repair
• Across lines, deep, large
• Granulation tissue
• Hypertrophic scar
• Keloid

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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

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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

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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

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Apocrine glands

• In axillary and genital area, breast
• Decapitation secretion
• Dependent on sex hormone
• Germs grow in moist area
• produce body odor

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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

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Blood vessels

• Supply the skin and appendages
• Regulate body temperature
• Sympathetic nerve make it constriction parasym.
  nerve, dilatation.

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Nerves

• Autonomic nerves vessels, sweat glands, smooth
  muscles
• Sensory nerves
• Subepidermal plexus
• Merckel plexus

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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.

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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

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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 35?m thick when
  dry, swell to 48 ?m on full hydration.

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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

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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

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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