Chapter 5
Lecture
Slides
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Chapter 5-Integumentary System
• What does
integument mean?
covering
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Functions
1. Protection:
water loss, microbes, UV light
2. Sensation:
hot, cold, pain, pressure
3. Temperature regulation:
helps maintain homeostasis
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4. Excretion and Absorption
removes waste, absorbs certain substances
5. Vitamin D production:
UV light stimulates production
6. Stores blood
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Skin Facts
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Largest organ
Used to determine body fat
Waterproof
Self-conditioning and healing
Reflects our emotions
Changes in color and appearance
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2 main regions
1. Epidermis
1. Dermis
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Epidermis
• Superficial, thinner layer
• Composed of keratinized stratified squamous
epithelium
• Keratinization:
- process in which new cells (with keratin) push
old cells to surface
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4 main types of cells
1. Keratinocytes
produce keratin that protects skin from
abrasions, heat, microbes
2. Melanocytes
produce melanin that contributes to skin
color and protects skin from UV rays
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3. Langerhan cells
help the immune system to recognize
invading microbes
4. Merkel cells
detect touch sensations
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Strata of Epidermis
• Stratum corneum:
- outermost layer of epidermis
- 20-30 layers of dead keratinized squamous cells
- accounts for 75% of epidermal thickness
- dandruff is this layer flaking off scalp
• Stratum lucidum
- found in thick skin areas
- contains keratin and thickened plasma membrane
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for added toughness
• Stratum granulosum
- consists of 3-5 layers that are undergoing
apoptosis
• Stratum spinosum
- consists of keratinocytes in 8-10 layers
- provides strength and flexibility
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• Stratum basale
- deepest layer of epidermis
- single layer of cells
- attaches to dermis
- stem cells undergo continuous cell
division
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DERMIS
• Thicker, deeper layer
• Divided into 2 regions:
1. Papillary – upper layer
2. Reticular – deeper layer
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Papillary layer
• thin connective tissue layer that contains blood
vessels, elastic fibers, collagen
• Dermal Papillae
- projections that extend up into the epidermis
- ridged on hands and feet – fingerprints
- remove wastes and help regulate body temp.
- Meissner corpuscles – nerve endings
sensitive to touch
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Reticular layer
• Contains:
- bundles of thick collagen
- hair follicles
- sweat and oil glands
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- Cleavage lines
- area where skin is most resistant to
stretching
- due to the orientation of collagen fibers
- important in scarring
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Hypodermis
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Below dermis
Not part of the skin
Attaches skin to underlying muscle and bone
Contains loose and adipose tissue
Storage area for fat
Has large blood vessels
Functions as padding and insulation
Contains Pacinian corpuscles – sensitive to
pressure
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Skin Color
• Effected by:
1. Melanin
- produced by melanocytes
- ranges from yellow to black
- amount produced is determined by genetics, UV
rays, and hormones
- All races have the same number of melanocytes.
The difference is the amount of pigment that is
produced.
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2. Hemoglobin:
- oxygen-carrying pigment that makes
blood red
3. Carotene:
- yellow-orange pigment found in plants
- accumulates in stratum corneum
4. Thickness of the stratum corneum
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Tanning and Sunburns
• Exposure to UV light stimulates melanocytes to
increase production of melanin
• Melanin builds up to help protect skin against UV
radiation (tan)
• A sunburn is the skin reacting to UV exposure
• UV light causes elastic fibers to clump and become
leathery
• UV light can alter DNA in cells causing them to
mutate (cancer)
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Temperature Regulation
• Body temp. should be 98.6o F
• Rate of chemical reactions (metabolism) is
altered by changes in temp.
• To cool body:
blood vessels in dermis dilate and heat is
transferred from deep in tissues to skin and
sweat is produced
• Too heat body:
blood vessels constrict to reduce blood flow to
skin and heat is retained
Skin Color and Disease
• Redness:
fever, hypertension, inflammation, allergies
• Pallor:
anemia or low blood pressure
• Jaundice:
liver disorder (yellow)
• Bronzing:
Addison’s disease (kidney disease)
• Bruising:
broken blood vessels
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Accessory Skin Structures
• Includes hair, skin glands, nails
HAIR
Functions:
- limited protection
- heat insulation
- touch
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Hair Components
• Shaft:
- superficial part of hair that
projects above the skin surface
• Root
- below the skin
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The shaft and root are made up of keratinized
cells arranged in 3 concentric layers.
1. Medulla
- inner layer
- contains pigment
2. Cortex
- middle layer
3. Cuticle
- outermost layer
- arranged like shingles on a roof
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• Hair follicle
- gives hair different shapes
- The base of each follicle is an onionshaped structure called a bulb.
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• Hair Bulb:
- contains blood vessels
- hair matrix – site of cell division
(where hair is made)
- sebaceous glands
- arrector pili – muscle, when contracted,
makes hair stand up (goose bumps)
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Growth Cycle
1. Growth stage
- new cells from the hair matrix are added to the
hair root
- existing cells are pushed upward and hair
grows longer
2. Regression stage
- hair follicle atrophies
3. Resting stage
- after resting stage, new growth cycle begins
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Hair Color
• Due to the amount and type of melanin in its
keratinized cells
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SKIN GLANDS
1. Sebaceous glands
- secrete sebum (oil)
- Functions of sebum:
- keeps hair/skin moist
- prevents excessive evaporation of
water from skin
- inhibits growth of some bacteria
- Acne – inflammation of sebaceous
glands
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2. Sweat glands
Types:
1. Eccrine
- respond to elevated body temps.
- open onto skin surface through
sweat pores
- start to function soon after birth
- release watery secretions
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2. Apocrine
- respond to emotional stress
- empty into hair follicles
- begin to function at puberty
- causes body odor
- release lipid-rich secretions
3. Ceruminous
- modified sweat gland that secretes
cerumen (earwax)
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Nails
Thin plate with layers of dead stratum
corneum cells with hard keratin
Functions:
1. protect ends of digits
2. ability to grasp
3. scratch
4. enhance manipulation
Nail Structure
• Nail body:
- visual part
• Nail root:
- covered by skin
• Cuticle:
- stratum corneum that extends into nail body
• Nail matrix:
- where cell division occurs
• Nail bed:
- attaches to nail
• Lunula:
- part of nail matrix
- whitish, crescent shaped area
- base of nail
• Free edge:
- extends past the digit
- white due to lack of capillaries
Aging and the Integument
• Skin becomes thinner due to decreased amounts
of collagen
• Decreased activity of sweat glands make temp
regulation more difficult
• Loss of elastic fibers cause skin to sag and
wrinkle
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• Decreased activity of sebaceous glands
make skin drier
• Loss of pigment in hair
• Age spots
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Classification of Burns
• 1st degree:
- damages only epidermis
- redness, slight swelling, pain
- usually no scar
• 2nd degree:
- damages epidermis and upper dermis
- redness, swelling, pain, blisters
- some scarring
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• 3rd degree:
- destroys epidermis and dermis
- no protection against environment
- nerve endings are destroyed
- no immediate pain
- can’t regulate body temp
- excessive fluid loss
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Skin Cancer
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Most common cancer
Mainly caused by UV light exposure
Fair-skinned people more prone
Prevented by limiting sun exposure and using
sunscreens
• UVA rays cause tan and is associated with
malignant melanomas
• UVB rays cause sunburns
• Sunscreens should block UVA and UVB rays
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Types of Skin Cancer
• Basal cell carcinoma:
- cells in stratum basale affected
- cancer removed by surgery
• Squamous cell carcinoma:
- cells above stratum basale affected
- can cause death
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• Malignant melanoma
- arises from melanocytes in a mole
- rare type
- metastasis is common
(metastasis – the spread of cancer to other
parts of the body)
- usually fatal
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