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CHAP 5: Integumentary System
Integument : skin, cutaneous membrane
- largest organ (7- 8% body weight)
- Integumentary System : Integument, nails, hair, sweat & sebaceous glands 2 Official layers:
- Epidermis: superficial
- Dermis: deeper layer
- Hypodermis: deepest layer ( Unofficially ) **Integument Functions
- Protection :** Selectively permeable, barrier 2. Prevention of H 2 O loss:
- insensible perspiration
- Sebaceous glands : sebum for lubrication of skin/hair **3. Temperature regulation
- Metabolic regulation:** UV radiation Vit D production calcium/phosphorus absorption **5. Immune defense: epidermal dendritic cells
- Sensory reception: tactile cells
- Excretion/Secretion:** sensible perspiration
LAYERS OF THE INTEGUMENT
EPIDERMIS: THE EPITHELIAL TISSUE
Most superficial; Avascular
Keratin ized stratified squamous epithelium : 4 to 5 strata of distinct cell types
Deep to superficial (as they grow):
Stratum basale - Deepest
1 layer next to dermis 3 cell types: 1.keratinocytes: Produce keratin , Divisible 2.melanocytes: Produce melanin 3.tactile cells: touch
Stratum spinosum
Several layers: Non-dividing, highly specialized keratinocyte, Desmosomes
4. Epidermal dendritic cells: phagocytes, Trigger immune response
Stratum granulosum
3 to 5 layers: Keratinization ; squamous shape Dying; strong and water-insoluble
Stratum lucidum (Dead)
Thin, translucent region, 2-3 layers thick thick skin only
Stratum corneum ( Dead )
Most superficial; 20 to 30 layers; Comprised of dead keratinocytes Anucleated; 1 month life; Microorganisms
Epidermal Variation: Thickness
Thick skin: 400-600 um
- Palms, fingers, toes, soles
- 5 layers: contains lucidum
- Sweat (eccrine) glands
Thin Skin : 75-150 um
- Most of body
- 4 layers: lacks lucidum
- hair follicles, sebaceous,
sweat (eccrine & apocrine)
glands
Number & thickness of epidermis NOT integument
Epidermal Variation: Skin Color
Skin color is determined by three pigments:
• hemoglobin: pink (or blue)
• melanin: genes, increases with UV light
• carotene: yellow-orange pigment from food
– Builds in stratum corneum
DERMIS
The Dermis
• Deep to the epidermis:
2 layers of connective tissues :
Papillary:
• areolar tissue
Reticular:
• dense irregular tissue
The Reticular Layer
• Majority of the
dermis
• Collagen fibers,
blood vessels ,
glands, hair
follicles, and nerves
HYPODERMIS (UNOFFICIALLY)
ACCESSORY ORGANS
Epidermis
Epidermal Derivatives
• Structures that grow from invaginations of
the epidermis into dermis:
– Nails
– Hairs
– Glands
Nails
• Derived from the
stratum corneum
• Cells densely packed w/
parallel fibers of hard
keratin
• Protection of digits
- Review on own and on models
ACCESSORY ORGANS: HAIR
Hair (pilus)
3 Types:
– Lanugo
– *Vellus
– Terminal
eyebrows/lashes,
pubic, axillary (arms,
legs, beards of men)
Hair
• Columns of keratinocytes
growing from follicles
• Dermis or hypodermis
• 3 zones from deep to
superficial:
- Hair bulb
- Hair root
- Hair shaft
• Arrector Pili Muscle
***** On own and on lab models
