Chapter 5
The Integumentary System
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Introduction
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The organs of the integumentary system
include the skin and its accessory structures
including hair, nails, and glands, as well as
blood vessels, muscles and nerves
Dermatology is the medical specialty for the
diagnosis and treatment of disorders of the
integumentary system.
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Structure of the Skin: Objectives
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Describe the layers of the epidermis and the
cells that compose them.
Compare the composition of the papillary and
reticular regions of the dermis.
Name the tissue types composing the
epidermis and dermis. List the major layers of
each and describe their functions.
Explain the basis for different skin colors.
Briefly describe how changes in skin color
may be used as clinical signs of certain
disease states.
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Structure of the Skin
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The skin (cutaneous membrane) covers the
body and is the largest organ of the body by
surface area and weight
Its area is about 2 square meters (22 square
feet) and weighs 4.5-5kg (10-11 lb), about
16% of body weight
It is 0.5 – 4 mm thick, thinnest on the eyelids,
thickest on the heels; the average thickness
is 1 – 2 mm
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Structure of the Skin
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It consists of two major layers:
outer, thinner layer called the epidermis,
consists of epithelial tissue
inner, thicker layer called the dermis
Beneath the dermis is a subcutaneous
(subQ) layer (also called hypodermis)
which attaches the skin to the underlying
tissues and organs.
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Components of the Integumentary System
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Structure of the Skin
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The epidermis has a number of important
characteristics:
the epidermis is composed of keratinized
stratified squamous epithelium
it contains four major types of cells: see next
slide
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Structure of the Skin
1. Keratinocytes (90% of the cells) produce
keratin which is a tough fibrous protein that
provides protection
2. Melanocytes: which produce the pigment
melanin that protects against damage by
ultraviolet radiation
3. Langerhans cells:
involved in immune
responses, arise from red bone marrow
4. Merkel cells: which function in the sensation
of touch along with the adjacent tactile discs
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Types of Cells in the Epidermis
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Epidermis
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The epidermis contains four major layers (thin
skin) or five major layers (thick skin)
1. Stratum basale (deepest layer) or stratum
germinativum, where continuous cell division
occurs which produces all the other layers
2. Stratum spinosum, 8-10 layers of keratinocytes
3. Stratum
granulosum,
which
includes
keratohyalin and lamellar granules
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Epidermis
5. Stratum lucidum is present only in thick skin (the
skin of the fingertips, palms, and soles)
6. Stratum corneum: composed of many sub layers of
flat, dead keratinocytes called or squames that are
continuously shed and replaced by cells from deeper
strata; constant friction can stimulate formation of a
callus.
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Keratinization, the accumulation of more and more
protective keratin, occurs as cells move from the
deepest layer to the surface layer
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Layers of the Epidermis
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Dermis
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The
dermis
has
several
important
characteristics:
is composed of connective tissue collagen and
elastic fibers
contains two layers
1. papillary region (upper layer immediately
beneath
epidermis)
consists
of
areolar
connective tissue containing thin collagen and
elastic fibers, dermal papillae (including capillary
loops), corpuscles of touch and free nerve
endings
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Dermis
2. reticular region, the deep layer, consists
of dense irregular connective tissue
containing collagen and elastic fibers
adipose cells, hair follicles, nerves,
sebaceous (oil) glands, and sudoriferous
(sweat) glands
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Dermis
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Lines of cleavage - “tension lines” in the skin
indicate the predominant direction of
underlying collagen fibers
Epidermal ridges reflect contours of the
underlying dermal papillae and form the basis
for fingerprints (and footprints); their
function is to increase firmness of grip by
increasing friction.
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05_01bc
Basis of Skin Color
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Variations in skin color arise from variations in
the amounts of three pigments: melanin,
carotene, and hemoglobin
Melanin - a yellow-red or brown-black pigment
produced by melanocytes (located mostly in the
epidermis, where it absorbs UV radiation)
The amount of melanin causes the skin’s color
to vary from pale yellow to tan to black
The number of melanocytes are about the same
in all people; differences in skin color is due
to the amount of pigment produced
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Basis of Skin Color
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A benign localized overgrowth of melanocytes is a
nevus or mole
Albinism is an inherited inability to produce melanin
- vitiligo is a condition in which there is a partial or
complete loss of melanocytes in patches of skin
Carotene - yellow-orange pigment (found in the
stratum corneum, dermis, and subcutaneous layer)
Hemoglobin - red color (located in erythrocytes
flowing through dermal capillaries)
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A, B, C ’ s of Melanoma
A.
B.
C.
D.
E.
Asymmetry
Borders
Color
Diameter
Elevation
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05_08
Subcutaneous Layer
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Subcutaneous layer (hypodermis) is not
part of the skin but, among its functions, it
attaches the skin to the underlying tissues
and organs; this layer (and sometimes the
dermis) contains lamellated (pacinian)
corpuscles which detect external pressure
applied to the skin.
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Accessory Structures of the Skin:
Objectives
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Compare the structure and locations of
sweat
(sudoriferous),
oil
(sebaceous),
ceruminous, and mammary glands. Also
compare the composition and functions of
their secretions.
Compare and contrast eccrine and apocrine
glands.
List the functions of hair.
Describe the cause of acne and its
treatments.
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Accessory Structures of the Skin
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include hair, skin glands, and nails
Hairs (pili) have a number of important
functions:
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protection
reduction of heat loss
sensing light touch
Sebaceous (oil) glands are connected to
hair follicles
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Skin Glands
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Sebaceous glands secrete an oily substance
called sebum which prevents dehydration of
hair and skin, and inhibits growth of certain
bacteria
Sudoriferous (sweat) glands – 2 types:
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Eccrine sweat glands
Apocrine sweat glands
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05_table_03
Acne
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Inflammation of sebaceous glands
Usually begins at puberty when sebaceous glands
grow and increase production
Androgens play the greatest role
Due to colonization of glands by bacteria that grow
and thrive in lipid-rich sebum
May cause a cyst of sac of connective tissue cells
that can destroy and displace normal tissue with a
scar
Treatment c/o benzoyl peroxide or tretinoin,
antibiotics (tetracycline or erythromycin) and
isotretinoin (accutane).
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Ceruminous and Mammary Glands
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Modified sudoriferous (apocrine) sweat
glands located in the ear canal and breast,
respectively
Along with nearby sebaceous glands,
ceruminous glands are involved in producing
a waxy secretion called cerumen (earwax)
which provides a sticky barrier that prevents
entry of foreign bodies into the ear canal.
Mammary glands produce milk
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Types of Skin: Objectives
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Compare and contrast structural and
functional differences of thick and thin skin.
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05_table_04
Functions of the Skin: Objectives
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Describe how skin contributes to:
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regulation of body temperature
blood reservoir
protection
cutaneous sensations
excretion and absorption
synthesis of vitamin D
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Functions of the Skin
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regulation of body temperature: liberating
sweat on its surface and adjusting flow of
blood in the dermis.
blood reservoir: 8-10% of total blood flow in a
resting adult
Protection: keratin barrier, lipids serve as
barrier and resist dehydration, acid pH,
pigment blocks UV, immunologic barrier
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Functions of the Skin
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cutaneous sensations: touch, pressure,
vibration, and tickling; pain
excretion and absorption: small role in
excretion of wastes – ammonia and urea;
absorption of water soluble substances is
negligible, but some lipid soluble materials
such as drugs and vitamins K, E, D, and A;
steroids
synthesis of vitamin D: requires UV activation
then converted to calcitriol in the kidneys
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Skin Wound Healing: Objectives
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Explain epidermal and deep wound healing.
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Epidermal Wound Healing: superficial
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Deep wound healing: four phases
1.
2.
3.
4.
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Inflammatory
Migratory
Proliferative
Maturation
Fibrosis – scar
Hypertrophic scar - keloid
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Deep Wound Healing
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Aging and the Integumentary System
Effects begins in late 40’s:
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Wrinkling, loss of collagen and elastic tissue
decrease of skin’s immune responsiveness: Langerhans cells
decrease and macrophages less effective
dehydration and cracking of the skin: decreased size of
sebaceous glands
decreased sweat production
decreased numbers of functional melanocytes resulting in gray
hair and atypical skin pigmentation
loss of subcutaneous fat
a general decrease in skin thickness
an increased susceptibility to pathological conditions: skin heals
poorly, increased risk skin cancer and pressure sores develop
more readily
growth of hair and nails decreases; nails may also become more
brittle with age.
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Burns
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Tissue damage from excessive heat, electricity,
radioactivity, or corrosive chemicals that destroys
(denatures) proteins in the exposed cells is called a burn.
Generally, the systemic effects of a burn are a greater
threat to life than are the local effects.
Depending on the depth of damage, skin burns are
classified as first-degree and second-degree (partialthickness) and third-degree (full-thickness) (Figure 5.9)
The seriousness of a burn is determined by its depth,
extent, and area involved, as well as the person’s age and
general health. When the burn area exceeds 70%, over half
of the victims die.
A method for determining the extent of a burn is the rule of
nines method (Figure 5.10).
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Burns
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1.
2.
3.
4.
5.
The injury of skin tissues results in severe
systemic effects:
Large loss of water, plasma, and plasma
proteins may result in shock
Risks of bacterial infections markedly
increased
Reduced circulation of blood results
Decreased urine output
Markedly diminished immune responses
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05_09
05_10
End of Chapter 5
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