Chapter 5
The Integumentary
System
Copyright 2009, John Wiley & Sons, Inc.
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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
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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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Functions
Covers and protects
the body
What does the skin
protect us from?
1.
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Pathogens
Injury
Ultra-violet radiation
2. Vit. D synthesis
Functions
3. Regulate body
temperature
How does it regulate
temperature?
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Sweating
Dilate/constrict of
blood vessels
Goose bumps
Functions
4. Excretes Waste
What
wastes are
excreted?
Urea
as sweat
subcutaneou
Functions
5. Reduces water loss
Keeps the body from drying out!
Functions
6. Houses sensory receptors
Chemo
Mechano
Chemo
Photo
Mechano
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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Overview of Epidermis
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Stratified squamous
epithelium
Contains no blood vessels
4 types of cells
5 distinct strata (cell layers)
Keratinocytes (90% of cells
produce keratin, a tough,
fibrous protein that provides
protection
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Cell types of the Epidermis
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Keratinocytes--90%
produce keratin
Melanocytes-----8 %
 produces melanin
pigment
 melanin transferred to
other cells with long cell
processes
Langerhan cells
 from bone marrow
 provide immunity
Merkel cells
 in deepest layer
 form touch receptor with
sensory neuron
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Epidermis
What do we find in the epidermis?
Melanocytes
What are melanocytes?
Cells that produce melanin.
What is melanin?
A dark brown pigment
What does melanin do?
Gives skin it’s color
Protects sensitive dermis from U-V radiation
Layers of the Epidermis
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Epidermis
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The epidermis contains 4 (thin skin) or 5 (thick skin) major layers
Stratum basale (deepest layer) or stratum germinativum, where
continuous cell division occurs which produces all the other layers
Stratum spinosum, 8-10 layers of keratinocytes
Stratum granulosum, which includes keratohyalin and lamellar
granules
Stratum lucidum is present only in thick skin (the skin of the fingertips,
palms, and soles)
Stratum corneum: composed of many sublayers of flat, dead
keratinocytes called corneocytes or squames that are continuously
shed and replaced by cells from deeper strata; constant friction can
stimulate formation of a callus.
Keratinization, the accumulation of more and more protective keratin,
occurs as cells move from the deepest layer to the surface layer
Dandruff - an excess of keratinized cells shed from the scalp
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Dermis
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Connective tissue layer composed of collagen & elastic
fibers, fibroblasts, macrophages & fat cells
Contains hair follicles, glands, nerves & blood vessels
Major regions of dermis
 papillary region
-superficial
 reticular region
- deep
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Papillary Region - superficial
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Composed of loose CT & elastic fibers
Finger like projections called dermal papillae
Functions
 anchors epidermis to dermis
 contains capillaries that feed epidermis
 contains Meissner’s corpuscles (touch) & free nerve endings
(pain&temp)
- Dense irregular connective tissue
- Contains interlacing collagen and elastic fibers
- Packed with oil glands, sweat gland ducts, fat & hair follicles
- Provides strength, extensibility & elasticity to skin
- stretch marks are dermal tears from extreme stretching
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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.
Dermatoglyphics - the study of the pattern
of epidermal ridges
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Skin Color
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Three pigments contribute to skin color
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Melanin – yellow to reddish-brown to black
pigment, responsible for dark skin colors
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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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Melanocytes
Do some people have
more melanocytes
than other people?
Can your skin turn orange if you eat too many carrots?
www.steelgirl.com/carrot3.htm
Subcutaneous Layer
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Subcutaneous (subQ) layer (also called
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
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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
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Accessory Structures of the Skin - Hair
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Hair is composed of dead, keratinized epidermal cells
Hair consists of:
shaft which mostly projects above the surface of the skin
root which penetrates into the dermis
hair follicle
epithelial root sheath
dermal root sheath
Functions of Hair:
Prevents heat loss
Decreases sunburn
Eyelashes help protect eyes
Touch receptors (hair root plexus) senses light touch
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Accessory Structures of the Skin
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There are different types of hairs including
lanugo, vellus hairs and terminal hairs
Hair color is determined by the amount and
type of melanin
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
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Histology of skin glands
Sudoriferous (Sweat) Glands
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Numerous eccrine (or merocrine) sweat glands
helps to cool the body by evaporating, and also
eliminates small amounts of wastes
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Apocrine sweat glands, located mainly in the skin of
the axilla, groin, areolae, and bearded facial regions of
adult males.
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their excretory ducts open into hair follicles- this sweat is
secreted during emotional stress and sexual excitement.
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Modified Sweat Glands
1. Ceruminous Glands
Along with nearby sebaceous glands, they 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.
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2. Mammary Glands
secrete milk
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Nails
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Nails are composed of hard, keratinized
epidermal cells located over the dorsal
surfaces of the ends of fingers and toes
Each nail consists of:
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free edge
transparent nail body (plate) with a whitish
lunula at its base
nail root embedded in a fold of skin
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Nails
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Epidermal Wound Healing
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Deep Wound Healing
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Development of the Integumentary
System
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The epidermis develops from the ectoderm;
nails, hair, and skin glands are epidermal
derivatives - the epidermis of a fetus is
protected by a fatty substance called vernix
caseosa
The dermis develops from the mesoderm
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Aging and the Integumentary System
Effects:
• wrinkling
• decrease of skin’s immune responsiveness
• dehydration and cracking of the skin
• 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
 Growth of hair and nails decreases; nails may also
become more brittle with age.
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Skin Cancer
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Basal cell carcinoma – least
malignant, most common
Squamous cell carcinoma –
keratinocytes in stratum
spinosum
Melanoma – metastasize
rapidly
End of Chapter 5
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