Anatomy and physiology of skin and soft tissue Acute and chronic wound p 報告者：蔡佩娟

Content 1.Anatomy of skin Introduction Skin layers – epidermis, dermis, hypodermis 2.Function of skin Protection Immune Thermoregulation Metabolism Communication 3.Factors altering skin characteristics

Anatomy of skin 1. Human skin is divided into two layers a. epidermis (outermost) b. dermis ( innermost) 2. separated by basement membrane (BM) 3. A layer of loose connective tissue beneath the dermis called hypodermis, or subcutis

The Human Skin 1. Average about 3000 square inches or 2 square meters. 2. Weighs about 6 pounds (15% of BW) 3. The largest organ 4. Receives 1/3 of the body’s blood volume 5.Varies in thickness (0.5mm~6mm)

Skin layers 1. Epidermis stratum corneum stratum lucidum stratum granulosum stratum spinosum stratum basale (germinativum) 2. Basement membrane 3. Dermis papillary dermis reticular dermis 4. Hypodermis

Epidermis 1. the outermost layer 2. derived from ectoderm 3. relatively uniform in thickness (75~150 μm, except soles and palms 0.4~0.6mm) 4. constantly being renewed (26~42 days) 5. divided into five layers.

Stratum Corneum 1. composed of dead keratinized cell (thin, stacked, pancake, anucleate cells) 2.abraded by daily trauma 3.80% are filled with keratin 4.Keratin -- “hard” in hair and nails “soft” in normal skin

Stratum Lucidum 1. in areas where the epidermis is thicker -- the palms, the soles 2. absent from thinner skin -- eyelid 3. one to five cells thick 4. a transitional layer where active lysosomal enzymes degrade the nucleus and organelles

Stratum Granulosum 1. one to five cells thick 2. keratohyalin granules present in the keratinocytes 3. contain profilaggrin, intermediate keratin filaments, loricrin– help to organize the keratin filaments 4. intensely stained by acid and basic dyes 5. still have active nuclei

Stratum Spinosum 1. decribed as the prickly layer due to morphology (polyhedral) 2. prominent feature – desmosome, a type of cell-cell junction 3. Synthesize involucrin– a soluble precursor of cornified envelopes

Stratum Basale 1. the innermost epidermal layer 2. a single layer of mitotically active cells called basal keratinocytes or basal cells 3. upward migration can take 2~3 weeks

Dermis (corium) 1. The thickest layer of skin ( 2 ~ 4 mm, average 2 mm), the back is most thick 2. derived from mesoderm 3. vascularized and innervated. 4. a network of papillary loops, supported by a deep horizontal plexus 5. major proteins: collagen, elastin 6. divided into papillary dermis and reticular dermis

Hypodermis 1. a superficial fascia below the dermis 2. an adipose layer containing subdermal plexus of blood vessels 3. provide insulation, reserve of energy, cushioning 4. Werner’s syndrome, Scleroderma lack this layer

Major functions of skin 1. Protection 2. Immunity 3. Thermoregulation 4. Sensation 5. Metabolism 6. Communication

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