Chapter 5 The Integumentary System
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End of Chapter 5
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Integumentary System
The body’s covering Includes: skin, nails, and hairs Skin: cutaneous membrane
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Structure
Two main parts
Epidermis - surface epithelial layer Dermis - deeper connective tissue layer
Subcutaneous (subQ) layer or hypodermis lies deep to dermis; is not part of the skin
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Integumentary System
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Epidermis
Keratinized stratified squamous epithelium Cell types (4):
Keratinocytes Melanocytes Langerhans cells Merkel cells
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Epidermal Cells
Keratinocytes
90% of epidermal cells 4-5 layers Produce keratin Protects skin Waterproofs skin
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Epidermal Cells
Melanocytes
Produce melanin that gives color to skin, hairs Transfer pigment to keratinocytes Make up 8% of epidermal cells
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Epidermal Cells
Langerhans cells
Immune response
Merkel cells
Sense of touch
Consist of tactile disc and neuron for touch sensation
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Epidermal Layers
Four Layers (strata)
Stratum basale
Stratum spinosum: 8-10 cell layer
Cells beginning to look flattened
Stratum granulosum makes keratin
Includes stem cells; new cells arise here
Losing cell organelles and nuclei Have waterproofing lipid
Stratum corneum: flattened dead cells
Cells here consist mostly of keratin. Cells here are shed and replaced from below.
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Skin Color
Melanin: dark color
Carotene: yellow orange
Darkness depends on amount of melanin produced. Provides some protection against UV rays In stratum corneum and adipose layers-
Hemoglobin in blood: pink-red
Depends on blood flow
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Accessory Structures
Hair Skin glands Nails
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Hair
Found on most skin surfaces
Made of fused keratinized cells Consists of shaft and root Surrounded by hair follicle
Not on palmar surfaces of hand and fingers or plantar surfaces of feet
Base is bulb which includes growing matrix producing cells
Nerves in hair root plexuses Muscle that pulls on hair: arrector pili Causes hair to stand on end Copyright 2010, John Wiley & Sons, Inc.
Hair
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Glands
Sebaceous gland: secrete oily sebum
Sudoriferous (sweat) gland
Connected to hair follicles; keeps hair from drying out Eccrine sweat gland Wide distribution- thermoregulation Apocrine sweat gland Axilla, groin, areolae, beard Contain other cell material
Ceruminous (wax) gland
Wax combines with sebum to produce earwax
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Nails
Plates of packed hard dead keratinized cells Nail body: major visible portion Free edge: part extending past finger or toe Root: cells deep to here (in nail matrix) form new nail cells
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Nails
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Nails
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Functions
Temperature regulation Protection Sensory reception Excretion and absorption: small amounts Vitamin D synthesis
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Aging
Adolescence: can develop acne Most effects in dermis, with visible signs of aging by about age 40. These include:
Loss of collagen fibers Loss of elasticity Loss of immune responses Decreased melanocyte functions:
gray hair, skin blotches
Thinning of skin and hairs
Anti-aging treatments Copyright 2010, John Wiley & Sons, Inc.
