Ch. 5- Integumentary System
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The Skin and the Hypodermis
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Skin- our largest organ
Accounts for 7% of our body weight
Varies in thickness from 1.5 to 4.4cm
Divided into 2 distinct layers
Epidermis
Dermis
Hypodermis- lies deep to the dermis
Composed of areolar and adipose tissues
Not part of the integumentary system, but shares some of skin’s properties
o
5 important functions
1.
Protection
a.
Cushions organs and protects from bumps, chemicals, water, loss, UV radiation
2.
Body temperature regulation
a.
Capillary network and sweat glands heat loss
3.
Excretion
a.
Urea, salts, and water lost through sweat
4.
Production of vitamin D
a.
Epidermal cells use UV radiating to synthesize vitamin D
5.
Sensory reception
a.
Contains sense organs associated with nerve endings
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Epidermis
o
Is composed of keratinized stratified squamous epithelium
o
Contains 4 main cell types
Keratinocytes
Location- stratum spinosum; produce keratin, a fibrous protein
Melanocytes
Location- basal layer; manufacture and secrete pigment
Tactile epithelial cells (Merkel cells)
Location- basal layer; attached to sensory nerve endings
Dendritic cells (Langerhan’s cells)
Location- stratum spinosum; part of immune system; macrophage-like
o
Keratinocytes- most abundant cell type in epidermis
Arise from
deepest later of epidermis
Produce keratin, a tough fibrous protein
Produce antibiotics and enzymes
Keratinocytes are
dead at skin’s surface
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Layers of the Epidermis
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Stratum corneum
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Stratum lucidum (only in thick skin)
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Stratum granulosum
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Stratum spinosum
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Stratum basale (stratum geminativum)
1
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Stratum Basale
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Deepest layer of epidermis
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Attached to underlying dermis
