Transcript Chapter_Integumentary Systemx

Chapter 7:
Skin and Appendages
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Lesson 7-1 Objectives
• List six functions of the skin.
• Define stratum germinativum and stratum
corneum.
• Describe the two layers of the
skinepidermis and dermis.
• List the two major functions of the
subcutaneous layer.
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Introduction
Skin (integument) is body’s
largest organ
 Integumentary system describes
the skin and its appendages—the
hair, nails, and skin glands
 You shed about 1.5 lbs per year
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Skin Perspective
• On average, 1 cm2 of
skin contains:
– 3,000,000 cells
– 10 hairs
– 15 sebaceous glands
– 3 feet of blood vessels
– 700 sweat glands
– 3000 sensory cells at
nerve endings
– 12 feet of nerves
• 200 pain receptors
• 2 cold receptors
• 12 sensors for heat
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Functions of the Skin
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Serves as mechanical barrier
Protects internal structures
Participates in the immune response
Acts as a gland for vitamin D synthesis
Performs excretory function
Performs sensory role
Helps regulate body temperature
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Structure of the Skin
• Layers
– Epidermis
• (lays upon dermis)
– Dermis (skin)
• Subcutaneous
• a.k.a: Hypodermis
• Accessory
structures
• Hair, nails,
glands..etc.
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Overview Structure of the Skin
Skin classified as cutaneous membrane
Two primary layers—epidermis and dermis;
joined by dermoepidermal junction
Hypodermis lies beneath dermis
Thin and thick skin (Figure 7-3)
“Thin skin” —covers most of body surface (1 to 3
mm thick); has hair and smooth surface
 “Thick skin”—soles and palms (4 to 5 mm thick);
ridged surface with no hair
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Layers of Epidermis
From deep to Superfical:
• Stratum Basale
• A.k.a Stratum Germinativum
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Stratum Spinosum
Stratum Granulosum
Stratum Lucidum
Stratum Corneum
2. **
3. 4.
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Layers uncovered
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Epidermis: Outer Layer continued…
• Layers of the epidermis
– Stratum corneum (surface layer); composed of
dead, flattened cells that slough off , our horns
– Stratum germinativum (deepest), a.k.a. stratum
basale: cells continuously dividing and moving
toward surface
• Keratinization: The protein keratin makes skin
cells hard, flat, and water resistant.
• (Keratinocytes…cells that actually produce
protein)
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Epidermal growth and repair
• Shortened turnover time increase thickness of
the stratum corneum; results in callus
formation
• Normally 10% to 12% of all cells in stratum
basale enter mitosis daily
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Structure of the Skin
Dermopidermal junction (DEJ)
A basement membrane
Polysaccharide gel serve to “glue” the
epidermis to the dermis below
Partial barrier to the passage of some cells
and large molecules
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Dermis
• Our “hide”, strong and stretchy
– “true skin”
• Lies under and supports the epidermis
– Gives strength
• Sits on the subcutaneous layer or hypodermis
• Embedded with accessory structures
– Includes blood vessels that nourish epidermis
– Reservoir storage for water and electrolytes
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Dermis continued…
• 2 major regions:
– Papillary: upper/superficial dermal layer
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Pain receptors (free nerve endings)
Touch receptors: Meissner’s corpuscles
Allow for grip
Genetically unique= fingerprints
Arrector pili (goose bumps)
– Reticular: Deepest of skin layer
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Blood vessel, sweat glands, oil glands
Pacinian corpuscles: Deep pressure receptors
Last line of defense
Leather
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Dermis (cont)
During wound healing
fibroblasts begin forming an unusually
dense mass of new connective fibers
if not replaced by normal tissue, this
mass remains a scar
Cleavage lines (Figure 7-7)—patterns
formed by the collagenous fibers of the
reticular layer of the dermis
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also called Langer’s lines
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Langer’s lines
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Scar formation
• Cleavage lines - patterns formed by the
collagenous fibers of the reticular layer also
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Subcutaneous Layer: Hypodermis
• A.k.a = subcutaneous layer
• Connection point to tissue that lies beneath
skin
• Highly vascularized
• Two main roles:
– Its fat insulates body from extreme temperature
changes.
– Its connective tissue anchors the skin to
underlying structures.
• NOT PART OF THE SKIN
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Problems…
• Decubitus ulcers; Bed
sores
– Blood supply is cut off
– Bedridden patients who
are not regularly moved
– Pressure of bone on skin
eventually cuts off
supply line
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Real life…
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Skin Color
Determined by: genes, physiology,
and sometimes pathology
Dark pigment: Melanin
• Eumelanin-dark brown-black
• Pheomelanin-red-brown
• Melanocyte= Make melanin
in epidermis(St.Basale)
• Melanocyte malfunctions:
– Albinism (defect in melanin)
– Vitiligo (loss of brown pigment)
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Skin color continued
• Beta-carotene: Orange-yellow (some veggies)
– Presence of melanin overshadows carotene’s tint
in most people
• Lipofuscin: brown-yellow age spots
• Hemoglobin
– Red coloring from blood cells in dermis capillaries
– Oxygen content determines the extent of red
coloring
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Skin Color (cont’d.)
• Physiological changes:
– Blushing: Blood vessel dilation
– Pallor: Blood vessel constriction
• Pathological changes:
– Cyanosis or bluish tint: Poor oxygenation
– Jaundice or yellowing: Bilirubin deposition (Bile
and Liver products)
– Bronzing: Melanin overproduction
– Ecchymosis: Black and blue bruising
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Accessory Structures: Hair
• Functions: Detect
insects, protect eyes,
keep dust out of lungs
• Hormones affect
growth.
• Melanin influences
color.
• Hair arises in epidermis.
• Cosmetic role
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Developmental of Hair
• Distribution-over entire body
– Except palms and soles of feet
• Lanugo: fine and soft hair before birth
• Vellus Hair: fine, barely noticeable hair,
childhood
• Body Hair
– Head hair
– Androgenic Hair: Coarse body hair
– Terminal Hair: coarse pubic hair and axillary hair
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Make up of hair
• Papilla—cluster of capillaries under germinal
matrix; “feed” follicle
• Root(hair follicle): part of hair embedded in
follicle in dermis but hair develops from
epidermis
• Shaft—visible part of hair
• Medulla—inner core of hair
• Cortex—outer portion
– What conditioner works on
• Growth is erratic
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Accessory Structures: Nails
• Protect tips of fingers and toes from injury
• Condition affected by oxygenation of blood
supply, trauma, and nutritional deficiencies
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Nails
• Consist of epidermal cells converted to hard
keratin
• Nail body—visible part of each nail
– It is what you trim
• Root—part of nail in groove hidden by fold of
skin, the cuticle
• Lunula—moon-shaped white area nearest
root
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Nails continued…
• Nail bed—layer of epithelium under nail body;
contains abundant blood vessels
– Appears pink under translucent nails
• Nails may have pigmented streaks
• Growth—nails grow by mitosis of cells in
statum basale beneath the lunula
– Average growth about 0.5 mm per week, or
slightly over 1 inch per year
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Accessory Structures: Glands
• Sebaceous glands:
– Oil glands
– Secrete sebum and in
fetus vernix caseosa
• Sudoriferous
– Sweat glands
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Sudoriferous Glands
• Apocrine glands: Found with hair follicles;
more active at puberty
– Axillary and Genital Regions
• Eccrine glands: Everywhere; Critical for
temperature regulation
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Eccrine glands
• Most numerous sweat
glands; quite small
• Over total body surface
• Simple, coiled, tubular
glands
• Function throughout life
• Secrete perspiration, or
sweat;
• Eliminate wastes and help
maintain a constant core
temperature
• Hyperhidrosis: over
sweating
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Apocrine gland
• Large; in subcutaneous layer
• Limited distribution—axilla,
areola of breast, and around
anus
• Simple, branched, tubular
glands
• Begin to function at puberty
• Thicker liquid full of nutrients
for bacteria
– causing B.O.
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Sweat and Its Function
Composition
 Mostly water
 Some metabolic waste
 Fatty acids and proteins (apocrine only)
Function
 Helps dissipate excess heat
 Excretes waste products
 Acidic nature inhibits bacteria growth
Odor is from associated bacteria
Sweet Sweat
Types of modified sweat glands:
• Mammary glands: Secrete milk
• Ceruminous glands: Secrete ear wax
(cerumen)
• Pheromones: Sex attractants
– Copuline (copulation)
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Black head vs. Pimple
• Sebaceous gland
closure
• Blackhead
– Partially clogged trapped
sebum
– Black due to oxygen
exposure
• Pimple
– Fully clogged pore
– Infected and inflamed
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Functions of the Skin (Table 7-2)
• Protection
– Physical barrier to microorganisms
– Barrier to chemical hazards
– Reduces potential for mechanical trauma
– Prevents dehydration
– Protects against excess UV exposure (melanin
function)
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Surface film
• Barrier formed by mixing sweat and
sebaceous glands with sloughed epithelial
cells from skin surface
• Functions
– Antibacterial, antifungal activity
– Lubrication
– Hydration of skin surface
– Buffer of caustic irritants
– Blockade of toxic agents
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Functions of the Skin
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Sensation
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Flexibility
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Skin acts as a sophisticated sense organ
Somatic sensory receptors detect stimuli that
permit us to detect pressure, touch,
temperature, pain, and other general senses
Skin is supple and elastic, thus permitting
change in body contours without injury
Excretion
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Water
Urea/ammonia/uric acid (small amounts)
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Functions continued…
• Hormone
– (vitamin D) production Exposure of skin
synthesizes vitamin D
– Blood transports = classified as a hormone
• Immunity
– Phagocytic cells destroy bacteria
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Body Temperature: Key Terms
• Core temperature: The inner parts of the body
• Shell temperature: The surface areas of the
body
• Thermoregulation: Balance of heat production
and heat loss
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Homeostasis of body
temperature
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Heat production
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By metabolism of foods in skeletal muscles
and liver
Chief determinant of heat production is the
amount of muscular work being performed
Heat loss
approximately 80% through the skin
remaining 20% through the respiratory,
digestive, and urinary tracts
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Temperature Regulation
• Hypothalamus
– Heat lost by:
• Dilation of blood
vessels
• Sweating
– Heat conserved by
• Shivering
• Blood vessel
constriction
• Less sweat
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Issues in Temperature Regulation
• Hyperthermia: Syncope (fainting), cramps,
heat exhaustion, heat stroke
• Hypothermia: Slowed metabolism, fibrillation
(random heart beat)
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Burns
Tissue damage and cell death caused by
heat, electricity, UV radiation, or chemicals
 Associated dangers
 Dehydration
 Electrolyte imbalance
 Circulatory shock
Burns: Classified by Depth
• Partial thickness
burns
– First-degree
– Second-degree
• Full-thickness burn
– Third-degree
• Extends to muscle
and bones
– Fourth degree
Severity of Burns
 First-degree burns
 Only epidermis is
damaged
 Skin is red and swollen
 Second degree burns
 Epidermis and upper
dermis are damaged
 Skin is red with blisters
 Third-degree burns
 Destroys entire skin layer
 Burn is gray-white or black
Types of Burns
1st Degree Burn
2nd Degree Burn
2nd vs. 3rd
Severe 2nd Degree Burn
3rd Degree Burn
RD
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Degree
Burns
Rules of Nines
 Way to determine the extent of
burns
 Body is divided into 11 areas for
quick estimation
 Each area represents about
9%
Rule of Nines
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Critical Burns
 Burns are considered critical if:
 Over 25% of body has second degree
burns
 Over 10% of the body has third degree
burns
 There are third degree burns of the face,
hands, or feet
Burns: Classified by Extent
• “Rule of
nines”
• Eschar (scab)
– Acts like a
tourniquet
– Breeds
bacteria
– Secretes
toxins
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Roman breastplate; escharotomy
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Cycle of Life: Skin
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Children
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Skin is smooth, unwrinkled, and
characterized by elasticity and
flexibility
Few sweat glands
Rapid healing
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Cycle of Life: Skin
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Adults
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Development and activation of
sebaceous and sweat glands
Increased sweat production; can
result in body odor
Increased sebum production; can
result in acne
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Cycle of Life: Skin
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Old age
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Decreased sebaceous and
sweat gland activity
 Wrinkling (Figure 7-24)
 Decrease in body's ability to
cool itself
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The Big Picture:
Skin and the Whole Body
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Skin is a major component of the
body’s structural framework
Skin defines the internal
environment of the body
Primary functions are support and
protection
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Skin Care
• All ages:
– Reduce exposure to UV radiation.
• Especially in older adults:
– Skin dries out more easily; retain moisture by
limiting excessive bathing and use of soap.
– Thinner skin bruises more easily and does not
insulate as well.
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Skin, Drugs, and Chemicals
• Skin can absorb many chemicals.
• Drug delivery systems:
• Hypodermic injections
• Transdermal patches
• Intradermal injections (allergy testing)
• Topical applications
• Danger of absorption of toxins
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