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PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky
The Integumentary System
Human Anatomy & Physiology, Sixth Edition
Elaine N. Marieb
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
5
The Integumentary System
 The skin and its derivates (sweat, and oil glands,
hairs and nails) make up a complex set of organs
that serves several functions mostly protectives.
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Skin (Integument)
 It covers the entire body, has a surface area of 1.2 to
2.2 m2 , weight 4 to 5 kg (aprox. 7% total body
weight). Varies in thickness from 1.5 to 4.0 mm.
 Consists of three major regions
 Epidermis – outermost superficial region
 Dermis – middle region
 Hypodermis (also called superficial fascia) –
deepest region
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Skin (Integument)
Figure 5.1
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Epidermis
 Composed of keratinized stratified squamous
epithelium, consisting of four distinct cell types and
four or five layers
 Cell types include keratinocytes, melanocytes,
Merkel cells, and Langerhans’ cells
 Outer portion of the skin is exposed to the external
environment and functions in protection
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Cells of the Epidermis
 Keratinocytes – produce the fibrous protein keratin.
 Melanocytes. Are found in the deepest part of
epidermis. – produce the brown pigment melanin. The
melanin granules accumulate on the superficial or
“sunny” side of the keratinocyte nucleus forming a
pigment that protects the nucleus from UV radiation.
 Langerhans’ cells – epidermal macrophages that help
activate the immune system.
 Merkel cells. Are present at the epidermal-dermal
junction – function as touch receptors in association
with sensory nerve endings.
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Layers of the epidermis
 The skin could be: 1.- Thick (covers the palms,
fingertips and soles of feet )
2.- Thin (covers the rest of body,
the stratum lucidum appears
to be absent)
 The epidermis consist in five layers: Stratum
basale, s. spinosum, s. granulosum, s. lucidum
and s. corneum (from deeper to superficial)
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Layers of the Epidermis: Stratum Basale
(Basal Layer)
 Deepest epidermal layer firmly attached to the
dermis
 Consists of a single row of the youngest
keratinocytes
 Cells undergo rapid division, hence its alternate
name, stratum germinativum
 10-25% of the cells are melanocytes. Ocassionally
Merkel cells are also seen in this stratum.
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Layers of the Epidermis: Stratum Basale
(Basal Layer)
Figure 5.2b
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Layers of the Epidermis: Stratum Spinosum
(Prickly Layer)
 It is several cell layer thick.
 Cells contain a weblike system of intermediate
filaments attached to desmosomes
 Melanin granules and Langerhans’ cells are
abundant in this layer.
 The keratinocytes in this layer appear irregular
(spiny) in shape, causing them to be called prickle
cells. However the spines do not exist in living cells.
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Layers of the Epidermis: Stratum Granulosum
(Granular Layer)
 Thin; consists in three to five cell layers in which
drastic changes in keratinocyte appearance occurs
 Keratohyaline and lamellated granules accumulate
in the cells of this layer. These make them more
resistant to destruction.
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Layers of the Epidermis: Stratum Lucidum
(Clear Layer)
 Appears as a thin, transparent band superficial to the
stratum granulosum
 Consists of a few rows of flat, dead keratinocytes
 Present only in thick skin
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Layers of the Epidermis: Stratum Corneum
(Horny Layer)
 Outermost layer of keratinized cells
 Accounts for three quarters of the epidermal thickness
 The shingle-like cell remnants of the s. corneum are referred
to as cornified, or “horny” cells.
 Functions include:
 Waterproofing
 Protection from abrasion and penetration
 Rendering the body relatively insensitive to biological,
chemical, and physical assaults
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Dermis
 Second major skin region containing strong, flexible
connective tissue
 Cell types include fibroblasts, macrophages, and
occasionally mast cells and white blood cells
 Composed of two layers – papillary and reticular
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Layers of the Dermis: Papillary Layer
 Papillary layer
 Areolar connective tissue with collagen and elastic
fibers
 Its superior surface contains peglike projections
called dermal papillae
 Dermal papillae contain capillary loops, Meissner’s
corpuscles, and free nerve endings
 On the palms of the hands and soles of the feet
these papillae lie atop larger mounds called dermal
ridges which form epidermal ridges (unique to each
of us)
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Layers of the Dermis: Reticular Layer
 Reticular layer
 Accounts for approximately 80% of the thickness
of the skin
 Collagen fibers in this layer add strength and
resiliency to the skin
 Elastin fibers provide stretch-recoil properties
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Hypodermis
 Subcutaneous layer deep to the skin
 Composed of adipose and areolar connective tissue
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Skin Color
 Three pigments contribute to skin color
 Melanin – yellow to reddish-brown to black
pigment, responsible for dark skin colors
 Freckles and pigmented moles – result from local
accumulations of melanin
 Carotene – yellow to orange pigment, most
obvious in the palms and soles of the feet
 Hemoglobin – reddish pigment responsible for the
pinkish hue of the skin
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Skin Color
 The skin color of some people is also influenced by
emotional stimuli, and many alterations in skin color
signal certain disease states:
- Redness or erythema
- Pallor or blanching
- Jaundice or yellow
- Bronzing
- Black and blue marks or bruises
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Sweat Glands (sudoriferous glands)
 Different types prevent overheating of the body; secrete
cerumen and milk. Two types: eccrine and apocrine
 Eccrine sweat glands – found in palms, soles of the feet,
and forehead. Composed by 99% water with some salts, Vit.
C, antibodies, dermicidin, and trace of metabolic waste.
 Apocrine sweat glands – found in axillary and anogenital
areas.
 Ceruminous glands – modified apocrine glands in external
ear canal that secrete cerumen. Block foreign material
 Mammary glands – specialized sweat glands that secrete
milk.
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Sebaceous Glands
 Simple alveolar glands found all over the body,
except on the palms and soles.
 Soften skin when stimulated by hormones.
 Secrete an oily secretion called sebum (hair follicle
or pore on skin surface).
 They are small on the body trunk and limbs but
quite large on the face, neck, and upper chest.
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Structure of a Nail
 Scalelike modification of the epidermis on the distal,
dorsal surface of fingers and toes
Figure 5.4
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Homeostatic imbalance
 Acne is an active inflammation of sebaceous glands
accompanied by “pimples” (pustule or cysts) on the
skin. It is usually caused by bacterial infection,
particularly by staphylococcus.
 Seborrhea known as “cradle cap” in infants, is
caused by overactive sebaceous glands.
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Hair
 Filamentous strands of dead keratinized cells
produced by hair follicles
 Contains hard keratin which is tougher and more
durable than soft keratin of the skin
 Made up of the shaft projecting from the skin, and
the root embedded in the skin
 Consists of a core called the medulla, a cortex, and
an outermost cuticle
 Pigmented by melanocytes at the base of the hair
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Hair Function and Distribution
 Functions of hair include:
 Helping to maintain warmth
 Alerting the body to presence of insects on the skin
 Guarding the scalp against physical trauma, heat
loss, and sunlight
 Hair is distributed over the entire skin surface except
 Palms, soles, and lips
 Nipples and portions of the external genitalia
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Hair Follicle
 Root sheath extending from the epidermal surface
into the dermis
 Deep end is expanded forming a hair bulb
 A knot of sensory nerve endings (a root hair plexus)
wraps around each hair bulb
 Bending a hair stimulates these endings, hence our
hairs act as sensitive touch receptors
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Hair Follicle
Figure 5.6a
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Hair Follicle
Figure 5.6c
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Types of Hair
 Hairs come in various sizes and shapes, but as a
rule they can be classified as:
 1.- Vellus – pale, fine body hair found in children
and the adult female
 2.- Terminal – coarse, long hair of eyebrows, scalp,
axillary, and pubic regions
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Homeostatic imbalance
 Hirsutism: Excessive hairiness, as well as other
signs of masculinization, may result from an adrenal
gland or ovarian tumor that secretes abnormally
large amounts of androgens. Since few women want
a beard or hairy chest, such tumors are surgically
removed as soon as possible.
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Hair Thinning and Baldness
A follicle has only a limited number of cycles in it.
Hair grows fastest from the teen years to the 40s,
then its growth slowly.
 Alopecia – hair thinning in both sexes
 True, or frank, baldness
 Genetically determined and sex-influenced
condition
 Male pattern baldness – caused by follicular
response to DHT
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Functions of the Integumentary System
 Protection:
1.- Chemical (skin secretion, ex: natural
antibiotic “defensin”, peptides called “cathelicidins”
prevent group A streptococcus bacteria infections,
and melanin)
2.- Physical (hardness of its keratinized cells)
3.- Mechanical barrier
4.- Biological barrier (include the Langerhans
cells of the epidermis, macrophages and DNA itself
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Functions of the Integumentary System
 Body temperature regulation is accomplished by:
 Dilation (cooling) and constriction (warming) of
dermal vessels
 Increasing sweat gland secretions to cool the body
 Cutaneous sensation – exoreceptors sense touch and
pain
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Functions of the Integumentary System
Sunlight modified cholesterol molecules in the skin
 Metabolic functions – synthesis of vitamin D in
dermal blood vessels
 Blood reservoir – skin blood vessels store up to 5%
of the body’s blood volume
 Excretion – limited amounts of nitrogenous wastes
are eliminated from the body in sweat
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Skin Cancer
 Most skin tumors are benign and do not metastasize
 A crucial risk factor for nonmelanoma skin cancers
is the disabling of the p53 gene
 Newly developed skin lotions (tiny oily vesicles
“lyposomes” filled with enzymes) that can fix
damaged DNA
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Skin Cancer
 The three major types of skin cancer are:
 Basal cell carcinoma
 Squamous cell carcinoma
 Melanoma
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Basal Cell Carcinoma
 Least malignant and most common skin cancer
 Stratum basale cells proliferate and invade the
dermis and hypodermis
 Slow growing and do not often metastasize
 Can be cured by surgical excision in 99% of the
cases
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Squamous Cell Carcinoma
 Arises from keratinocytes of stratum spinosum
 Arise most often on scalp, ears, and lower lip
 Grows rapidly and metastasizes if not removed
 Prognosis is good if treated by radiation therapy or
removed surgically
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Melanoma
 Cancer of melanocytes is the most dangerous type of
skin cancer because it is:
 Highly metastatic
 Resistant to chemotherapy
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Melanoma
The American Cancer Society suggest the evaluation of skin
tumors by ABCD rule.
 Melanomas have the following characteristics (ABCD rule)
 A: Asymmetry; the two sides of the pigmented area do not
match
 B: Border is irregular and exhibits indentations
 C: Color (pigmented area) is black, brown, tan, and
sometimes red or blue
 D: Diameter (spot) is larger than 6 mm (size of a pencil
eraser)
 E: Elevation above the skin surface, improve diagnosis
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Melanoma
 Treated by wide surgical excision accompanied by
immunotherapy
 Chance of survival is poor if the lesion is over 4 mm
thick
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Burns: Tissue damage inflicted by intense heat, electricity, radiation or
certain chemicals. CLASSIFICATION ACCORDING SEVERITY
 First-degree – only the epidermis is damaged
 Symptoms include localized redness, swelling, and
pain
 Second-degree – epidermis and upper regions of
dermis are damaged
 Symptoms mimic first degree burns, but blisters also
appear
 Third-degree – entire thickness of the skin is damaged
 Burned area appears gray-white, cherry red, or black;
there is no initial edema or pain (since nerve endings
are destroyed)
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Rule of Nines
 Estimates the severity of burns
 Burns considered critical if:
 Over 25% of the body has second-degree burns
 Over 10% of the body has third-degree burns
 There are third-degree burns on face, hands, or feet
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Rule of Nines: Body is divided into 11 areas (9%) + 1%(genital)
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Figure 5.8a
Developmental Aspects of the Integument: Fetal
 Epidermis develops from ectoderm
 Dermis and hypodermis develop from mesoderm
 Lanugo – downy coat of delicate hairs covering the
fetus (5-6 months)
 Vernix caseosa – substance produced by sebaceous
glands that protects the skin of the fetus in the
amnion (when baby is born)
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Developmental Aspects of the Integument:
Adolescent to Adult
 Skin and hair become oilier and acne may appear
 Skin shows the effects of cumulative environmental
assaults around age 30
 Scaling and dermatitis become more common
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Developmental Aspects of the Integument:
Old Age
 Epidermal replacement of cells slows and skin
becomes thinner
 Skin becomes dry and itchy
 Subcutaneous fat layer diminishes, leading to
intolerance of cold
 Decreased elasticity and loss of subcutaneous tissue
leads to wrinkles
 Decreased numbers of melanocytes and Langerhans’
cells increase the risk of skin cancer
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