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Chapter 5
The Integumentary System (IS)
Integument covering
Covers the outside of the body & is
easily observed
Can be used as a diagnostic tool for
determining health
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Chapter 5 Outline
I.  Overview of the Integumentary System
II.  Skin
III.  Hypodermis
IV.  Accessory Skin Structures
V.  Summary of Integumentary System
Functions
VI. Effects of aging on the Integumentary
System
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I. Overview of the IS
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I. Overview of the IS
Major Functions of the IS
1.  Protection
– 
– 
– 
Protects from abrasion & UV light
Prevents entry of microorganisms
Prevents water loss & thus dehydration
2.  Sensation
– 
Contains sensory receptors that detect temp, touch, pressure,
& pain
3.  Temperature Regulation
– 
Regulated via blood flow thru skin & activity of sweat glands
4.  Vitamin D Production
– 
When exposed to UV can produce molecules that may be
converted into Vit D
5.  Excretion
– 
Small amounts of wastes are excreted thru gland secretions
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II. Skin
A.  Epidermis
B.  Thick & Thin Skin
C.  Skin Color
D.  Dermis
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II. Skin
Epidermis
•  Most superficial & made
up of epithelial tissue
•  Resists abrasion on skin
surface
•  Reduces water loss thru
skin
Dermis
•  Epidermis sits on top of
dermis
•  CT
•  Responsible for most of
the structural strength of
the skin
Figure 5.1
Pg 150
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II. Skin: Epidermis
•  Strat. Squ. Epi
separated from the
dermis by a basement
membrane
•  Not very thick &
contains no blood
vessels relying on
diffusion for
nourishment
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Figure 5.2
Pg 152
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II. Skin: Epidermis
Cells that make-up the epidermis
1.  Keratinocytes
– 
– 
Most of the cells of the epi
belong is this category b/c
they prod a protein mixture
called keratin wh/ makes
cells hard
This is the reason cells resist
abrasion & reduce water loss
2.  Melanocytes
– 
Part of the immune system
4.  Merkel Cells
– 
Keratinocytes
Langerhans
Cells
Contribute to skin color
3.  Langerhans Cells
– 
Dead
Keratinocytes
Specialized cells associated
with nerve endings
responsible for detecting light
touch & superficial pressure
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Melanocytes
Merkel cells
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II. Skin: Epidermis
•  Cells of the epidermis are prod’d by mitosis in
the deepest epi layer, as new cells are
formed they push older cells toward the
surface where they slough off (Desquamate).
The outermost cells protect the deeper cells
•  Keratinization
–  Cells Δ shape & internal chemical composition
becoming filled w/keratin
–  These cells eventually die & prod the outer layer
of dead-hard cells that resist abrasion & forms a
permeability layer
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II. Skin: Epidermis
5 layers of the epidermis
Figure 5.3 pg 153
1.  Stratum Basale/
Stratum
Germinativum
2.  Stratum Spinosum
3.  Stratum Granulosum
4.  Stratum Lucidum
5.  Stratum Corneum
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II. Skin: Epidermis
5 layers
Figure 5.3 pg 153
1.  Stratum Basale
–  Structure
• 
• 
• 
Deepest layer of the epi
Single layer of cube to
columnar shaped cells
Basement membrane
attaches the SB to the
dermis
–  Function
• 
• 
• 
Prod’n of cells of the
• 
most superficial layers
• 
Melanocytes produce &
contribute to melanin in • 
cells wh/ protects
against UV
• 
Hemidesmosomes hold SB to
basement membrane
Desmosomes hold cells together
Keratinocytes undergo division
every 19 days
1 daughter pushes toward the
surface while the other stays in
the SB
40-56 days from start in SB to
slough off
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II. Skin: Epidermis 2.  Stratum Spinosum
5 layers
–  Structure:
• 
• 
• 
• 
8-10 layers of many sided
cells that flatten as the are
pushed toward the surface
Desmosomes are broken &
reformed
If cells are pulled apart they
take on a spikey appearance
thus the name
There are additional keratin
fibers & lipid filled organelles
(Lamellar granules)
–  Fxn:
• 
Production of keratin fibers &
formation of lamellar bodies
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II. Skin: Epidermis
5 layers
3.  Stratum Granulosum
– 
Structure
• 
– 
2 to 5 layers of flattened diamond
shaped cells
Function
• 
• 
• 
Prod’n of keratohyalin granules
(makes cells look grainy)
Lamellar bodies release lipids from the
cells
Cells die (nucleus & other organelles
degenerate but keratin fibers and
keratohyalin granules stay intact)
4.  Stratum Lucidum
– 
Structure
• 
• 
– 
3 to 5 layers of clear dead cells w/
indistinct boundaries
Appear transparent & normally only in
thick skin
Function
• 
Dispersion of keratohyalin around
keratin fibers
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II. Skin: Epidermis
5 layers
5.  Stratum Corenum
–  Structure:
• 
• 
Most superficial layer of the
epidermis
25 or more layers of dead
squamous cells (Cornified)
–  Fxn:
• 
Provision of structural strength by
keratin within cells Soft Keratin
– 
– 
• 
• 
Soft Keratin:
» 
Keratin fibers + keratohyalin
Hard Keratin:
» 
Found in nails & hair
Prevention of water loss via lipids
surrounding cells
Sloughing off the most superficial
layers resists abrasion
– 
– 
Desmosomes\ eventually break
XSV sloughing  dandruff
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II. Skin: Thick and Thin Skin
•  Classified based on the structure of the epidermis
•  “Thickness of the skin” (Epi + Dermis) varies dependent on location
ex/eyelid = 0.5mm shoulder/back = 5mm
•  Skin subjected to XSV friction or pressure will eventually develop a
callus (extra corneum) and these can develop on thick or thin skin
•  Corn cone shaped callus that extends deep into epidermis and can
be painful
Thick Skin
Thin Skin
•  All 5 epidermal layers &
stratum corneum has many
extra layers of cells
•  Found in areas subjected to
pressure & friction
•  Palms, fingers, & soles
•  4 epidermal layers
•  Covers the rest of the body
•  Granulosum often consists of
only 1 or 2 layers
•  Hair is only found on thin
skin.
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II. Skin: Skin Color
•  Skin color is determined by:
–  Pigments w/in the skin
–  Blood circulating thru the skin
–  Thickness of the Stratum Corneum
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II. Skin: Skin Color- Melanin
•  Group of pigments responsible for skin, hair, & eye color
•  Provides UV protection
•  High Melanin:
–  Freckles, moles, nipples, areolae of the breasts, axillae, & genitallia
•  Low Melanin:
–  Lips & palms
•  Originates from tyrosine & can be Δed into several different pigments
ranging from black/brown to red/yellow
Pg 156 Figure5.4
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II. Skin: Skin Color- Melanin
•  Melanin production is based on 3 things
1.  Genetic Factors
– 
– 
– 
– 
Different races or those w/in the same race
Amounts & types of melanin prod’d
Size, #, & distribution of melanosomes
# of melanocytes usually doesn’t Δ but amount of melanin
prod’d does
–  1 mutation can lead to albinism
2.  Exposure to light
–  Darkens the melanin that is present & stimulates the
prod’n of more
3.  Hormones
–  Pregnancy induces the prod’n of estrogen & melanocyte
stimulating hormone…thus increasing melanin prod’n
• 
• 
Line down middle of the belly, darkened nipples, areolae, &
genetalia, mask of pregnancy
Addison’s disease can also cause Δ in color
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II. Skin: Skin Color
Erythema
•  Bld flowing thru skin
imparts a reddish hue
•  Induced by:
Carotene
–  Inflammatory response
–  Colds, blushing, flushing
when angry or hot
•  Decrease in bld flow
(shock) can make skin
pale
•  Cyanosis: blue tint b/c of
lack of O2
•  Yellow pigment found in
plants (corn & carrots)
•  Usually ingested and
used as a source of Vit A
•  XS ingestion can cause a
discoloration (thus turning
the skin yellow-orange)
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II. Skin: Dermis
•  CT with a few adipocytes &
macrophages as well the
primary fiber is collagen
•  Compared to hypodermis the
bld vessels & adipose is
minimal
•  Present:
– 
– 
– 
– 
– 
Nerve endings
Hair follicles
Smooth muscles
Glands
Lymphatic vessels
•  If skin is overstretched
dermis may rupture leaving
epidermal scars called 
stretch marks
• Nerve endings
• Free nerve endings:
• Pain, itch, tickle, temp
• Hair follicle receptors
• Light touch
• Pacinian Corpuscle
• Deep pressure
• Meissner Corpuscle
• Detect simultaneous stimulation on 2
points on the skin
• Ruffini End organs
• Continuous touch or pressure
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2 major layers
1.  Reticular Layer
– 
– 
– 
II. Skin- Dermis
Deep layer composed of DICT
Continuous w/hypodermis & forms a
mat of irregularly arranged fibers that
are resistant to stretching in many
directions
Cleavage/tension lines elastin &
collagen arrangement that prod
patterns in skin (Stitching)
2.  Papillary Layer
– 
– 
– 
Superficial layer containing dermal
papillae that extend toward the
epidermis
Contains bld vessels that supply epi w/
nutrients & removes wastes as well as
aiding in body temp regulation
Thick skin responsible for finger
prints wh/ fxn in increasing friction &
improving grip
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III. Hypodermis
a.k.a. Subcutaneous tissue
a.k.a. Superficial Fascia
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III. Hypodermis
•  House Foundation Skin Hypodermis
•  Attaches to underlying bone & muscle, and
supplies upper layers w/bld vessels & nerves
•  Matrix Loose CT, collagen & elastic fibers
•  Cells: fibroblasts, adipose cells, & macrophages
•  ~ ½ of the bodies adipose is stored here
–  Fxns: insulation, energy, & padding
–  Amount varies with age and sex
•  Babies have more than adults
•  Women more than men in hips and breasts
•  Body shape can also change w/ fat stores
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IV. Accessory Skin Structures
A.  Hair
B.  Glands
C.  Nails
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IV. Accessory Skin Structures: Hair
•  Hair is found almost every
where except:
Figure 5.6 pg 159
–  Palms, soles, lips, nipples, external
genitalia, & distal segments of the
fingers & toes
•  Hair types:
–  Lanugo
•  5th-6th mo of fetal development
•  Delicate unpigmented hair
–  Terminal Hairs
•  Near birth
•  Long course pigmented hair replaces
lanugo on scalp, eyelids, & eyebrows
–  Vellus Hairs
•  Replace rest of body hair
•  Short, fine, usually unpigmented
–  Puberty: terminal hair replaces that
of armpit (axillary) and pubic
regions [Wicks/protects from
abrasion]
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•  Men chest, legs, arms
 90% terminal hair
•  Women 35%
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IV. Accessory Skin Structure: Hair
Hair Structure
•  Hair shaft: protrudes above the
surface
•  Hair Root: located below the
surface
•  Hair Bulb: expanded base of
root
•  3 concentric layers to hair root/
shaft
a.  Medulla
• 
Central axis of the hair 2-3 layers
of cells w/soft keratin
b.  Cortex
• 
Forms bulk of hair cells contain
hard keratin (more S in make-up)
c.  Cuticle
• 
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Single layer of cells that forms
hair surface & overlap like
shingles
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IV. Accessory Skin Structure: Hair
Hair Structure
•  Hair follicle consists of:
1.  Dermal Root Sheath
• 
Portion of the dermis that
surrounds the Epi root sheath
2.  Epithelial Root Sheath
a.  External
  All strata found in thin
skin toward hair shaft
but decreases as it goes
down until it is only the
stratum basale
b.  Internal
  Holds hair in place, and
when hair is pulled it
usually can be seen at
the base
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IV. Accessory Skin Structure: Hair
Hair Structure
Hair Color
•  Inside of the hair bulb
–  Matrix:
  mass of undifferentiated
epithelial cells which prod the
hair & the epithelial root sheath.
–  Hair Papilla:
  Dermis of the skin projects into
the hair bulb at the base and
contains blood vessels that
provide nourishment for the
cells of the matrix
•  Melanin is prod’d by melanocytes w/in hair bulb matrix
& is passed to keratinocytes in hair cortex & medulla
•  Varying amounts & types of melanin cause different
shades
•  W/ age amount of melanin in hair can decrease;
causing hair color to fade
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IV. Accessory Skin Structure: Hair
Hair Growth
•  Eyelashes:
•  Hair is prod’d in cycles
1.  Growth Stage
  Hair is formed by matrix cells
that differentiate, become
keratinized and die
  Hair grows longer as cells are
added to the base
2.  Resting Stage
  Hair growth stops hair follicle
shortens & hold hair in place
–  30 days growth
–  105 days rest
•  Scalp:
–  3 years growth
–  1-2 years rest
•  Ave. hair growth is 0.3mm a
day
•  Max hair length is
determined by rate of hair
growth & length of growing
phase
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IV. Accessory Structures: Muscles
•  Arrector Pili
–  Extend from the
dermal root sheath of
the hair follicle to the
papillary layer of the
dermis
–  This takes the hair
from oblique angle to a
more perpendicular
angle to the skin
surface (gooseflesh)
–  Cold or scared
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IV. Accessory Skin Structures: Glands
•  Major skin glands:
a.  Sebaceous glands
b.  Sudoriferous
1.  Eccrine
2.  Apocrine
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IV. Accessory Skin Structures: Glands
•  Major skin glands:
a.  Sebaceous glands
– 
– 
Located in the dermis
Simple/Compound alveolar
glands that produce sebum
• 
– 
– 
– 
– 
Oily white substance rich in
lipids
Holocrine glands b/c lysis &
death of cells that become
part of secretion
Connected via duct to hair
follicle
Prevents drying & protects
against some bacteria
Very few open to skin
surface
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IV. Accessory Skin Structures: Glands
•  Major skin glands:
b.  Sudoriferous
  Sweat glands
1.  Eccrine
• 
• 
• 
• 
Most common type found
almost everywhere (including
hands & soles of feet)
Simple, coiled, tubular glands
that open to skin surface
through pores
2 regions:
Deep coiled region (dermis)
– 
• 
• 
Produces sweat (isotonic fluid
that includes water, some salt,
small amounts of urea,
ammonia, uric acid, & lactic
acid)
Duct (passes to surface)
Help regulate temperature
2.  Apocrine
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IV. Accessory Skin Structures: Glands
•  Major skin glands:
b.  Sudoriferous
  Sweat glands
1.  Eccrine
2.  Apocrine
• 
• 
• 
• 
• 
Simple coiled tubular glands
that open into hair follicles
superficially to sebaceous
glands
In humans they are found in
the axillae, genitalia, and
around the anus
Do not regulate temperature
Only become active at puberty
as a result of sex hormone
stimulation
May be a sign of sexual
maturity.
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IV. Accessory Skin Structures: Glands
Other glands
•  Ceruminous Glands:
–  modified sweat glands located in the ear canal
produce cerumen (earwax) to protect eardrum
by preventing entry of dirt or small insects
•  Mammary Glands:
–  Modified apocrine sweat glands in breasts
designed to produce milk
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IV. Accessory Skin
Structures:
Nail
•  Distal ends of primate digit covered in nail
•  Fxn:
–  Protection
–  Manipulation & grasping of small objects
–  Scratching
•  Nail consists of 2 major parts:
A.  Nail Root (Proximal portion): covered by skin
B.  Nail Body (Distal Portion): visible portion
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IV. Accessory Skin
Structures:
Nail
• 
• 
• 
• 
Nail fold: Flaps of skin that cover the root & lateral edges
Nail grove: holds edges of nail in place
Eponychium: cuticle
Hyponychium: thickened portion of stratum corneum beneath
the free edge of the nail body
•  Nail Root extends distally from nail matrix, which produces the
majority of the nail
•  Nail bed holds the nail body
•  Lunula- cresent shaped area at the base of the nail that has
almost no color because it is thicker that the rest of the nail
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V. Summary of IS fxns
A.  Protection
B.  Sensation
C.  Temperature regulation
D.  Vitamin D Production
E.  Excretion
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V. Summary of IS Fxns
1. Protection
2. Sensation
•  Protects against abrasion,
UV-light, prevents entry of
microorganisms, helps
regulate body temperature,
& prevents water loss.
•  Hair protects against
abrasion & blocks UV-light
& is a heat insulator
•  Nails protect the ends of
digits
•  Skin contains sensory
receptors for:
– 
– 
– 
– 
– 
Pain
Touch
Hot
Cold
Pressure
•  These allow for proper
response to the
environment
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V. Summary of IS Fxns
3. Temperature Regulation
4. Vitamin D Production
•  Thru dilation &
constriction of blood
vessels, the skin controls
heat loss from the body
•  Sweat glands produce
sweat, which evaporates
& lowers body
temperature
•  Skin exposed to UV-light
produces cholecalciferol,
wh/ is modified in the liver &
then in the kidneys to form
active Vit D.
•  Vit D increases blood Ca
levels by promoting Ca
uptake from the intestine,
the release of Ca from the
bone, and the reduction of
Ca loss from the kidneys.
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V. Summary of IS Fxns
5. Excretion
•  Skin glands remove small
amounts of waste
products (i.e. urea, uric
acid, & ammonia) but are
not important to excretion
like the kidneys.
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VI. FX of aging on IS
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VI. Effects of aging on the IS
•  As the body ages, blood flow to the skin
declines, thus skin becomes thinner &
elasticity is lost
•  Sudoriferous & sebaceous glands are less
active and the number of melanocytes
also decreases
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