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Chapter 4
The Integumentary system
Figure 4.1 Functional Organization of the Integumentary System (1 of 2)
Cutaneous Membrane
Epidermis
Dermis
• Protects dermis from
trauma, chemicals
• Controls skin permeability,
prevents water loss
• Prevents entry of
pathogens
• Synthesizes vitamin D3
• Sensory receptors detect
touch, pressure, pain, and
temperature
• Coordinates immune
response to pathogens
and skin cancers
Papillary Layer
Reticular Layer
• Nourishes and
supports
epidermis
• Restricts spread of
pathogens
penetrating epidermis
• Stores lipid reserves
• Attaches skin to deeper
tissues
• Sensory receptors
detect touch, pressure,
pain, vibration, and
temperature
• Blood vessels assist in
thermoregulation
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Figure 4.1 Functional Organization of the Integumentary System (2 of 2)
Accessory Structures
Hair Follicles
Exocrine Glands
Nails
• Produce hairs that
protect skull
• Produce hairs that
provide delicate
touch sensations
on general body
surface
• Assist in
thermoregulation
• Protect and
support tips
of fingers and
toes
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• Excrete wastes
• Lubricate
epidermis
Layers of Skin
Figure 4.3
The Structure and Layers of the Epidermis
Epidermis
(five layers)
Surface
Characteristics
Stratum
corneum
• Multiple layers of flattened, dead, interlocking
keratinocytes
• Typically relatively dry
• Water resistant but not waterproof
• Permits slow water loss by insensible perspiration
Stratum
lucidum
• Appears as a glassy layer in thick
skin only
Stratum
• Keratinocytes produce keratohyalin and keratin
granulosum • Keratin fibers develop as cells become thinner
and flatter
• Gradually the cell membranes thicken, the
organelles disintegrate, and the cells die
Basal lamina
Epidermis of thick skin
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LM × 225
Stratum
spinosum
• Keratinocytes are bound together by maculae
adherens attached to tonofibrils of the cytoskeleton
• Some keratinocytes divide in this layer
• Langerhans cells and melanocytes are often present
Stratum
basale
• Deepest, basal layer
• Attachment to basal lamina
• Contains epidermal stem cells, melanocytes,
and Merkel cells
Dermis
Figure 4.2 Components of the Integumentary System (1 of 2)
Cutaneous
Membrane
Epidermis
Dermis
Papillary layer
Reticular layer
Subcutaneous layer
(hypodermis)
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Capillary loop of
subpapillary
plexus
Dermal Papilla & Epidermal Ridge
Epidermis
Epidermal
ridge
Dermal
papilla
Dermis
Figure 4.5
The Epidermal Ridges of Thick Skin
Pores of sweat
gland ducts
Epidermal
ridge
SEM × 25
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Stratum Basale & Melanocytes
Melanocytes
in stratum
basale
Melanin
pigment
Basal lamina
Thin skin
LM  600
This micrograph indicates the
location and orientation of
melanocytes in the stratum
basale of a dark-skinned person.
Melanosome
Keratinocyte
Melanin
pigment
Melanocyte
Basal
lamina
Melanocytes produce and store melanin.
Melanocytes & UV radiation
Albino animals
Stratum spinosum
This slide used a special stain so you can see
the Langerhan’s cells.
Stratum granulosum
-
Thin skin vs thick skin
Which of the following helps prevent skin
damage by absorbing ultraviolet radiation?
a. melanin
b. carotene
c. keratin
d. a and c
4. Skin can regenerate effectively even after
considerable damage because:
a) Epidermis of skin has rich supply of small blood
vessels
b) Fibroblasts in dermis give rise to new epidermal
germinal cells
c) Contraction in the injured areas bring cells of
adjacent strata together
d) Stem cells persist in both epithelial & CT
components of skin
The color of the epidermis is due to a
combination of all of the following EXCEPT the:
a) variable quantities of carotene and melanin.
b) dermal blood supply.
c) thickness of the stratum corneum.
d) amount of vitamin D.
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DERMIS
Figure 4.7a The Structure of the Dermis and the Subcutaneous Layer
Capillary loop of
subpapillary plexus
Dermal papillae
Epidermal
ridges
Papillary layer of dermis
Reticular layer
Subpapillary
plexus
Lymphatic vessel
Adipocytes
© 2015 Pearson Education, Inc.
Fi
*
Papillary layer
Cutaneous plexus
*
SEM × 649
a The papillary layer of the dermis consists
of loose connective tissue that contains
numerous blood vessels (not visible), fibers
(Fi), and macrophages (not visible). Open
spaces, such as those marked by asterisks,
would be filled with fluid ground substance.
Figure 4.7b The Structure of the Dermis and the Subcutaneous Layer
Capillary loop of
subpapillary plexus
Dermal papillae
Epidermal
ridges
Papillary layer
Reticular layer
Subpapillary
plexus
Cutaneous plexus
Lymphatic vessel
Adipocytes
Reticular layer of dermis
SEM × 1340
b The reticular layer of the dermis contains
dense, irregular connective tissue.
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Figure 4.7c The Structure of the Dermis and the Subcutaneous Layer
Capillary loop of
subpapillary plexus
Dermal papillae
Epidermal
ridges
Papillary layer
Reticular layer
Subpapillary
plexus
Cutaneous plexus
Lymphatic vessel
Adipocytes
Subcutaneous layer
c
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SEM × 268
The subcutaneous layer contains large
numbers of adipocytes in a framework of
loose connective tissue fibers.
Which of the following allows the skin to
stretch and recoil?
a) keratin
b) collagen
c) melanin
d) vitamin D
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Which of the following would be considered
the cutaneous layer?
a) dermis and hypodermis
b) epidermis and dermis
c) epidermis, dermis, and hypodermis
d) epidermis only
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Figure 4.9a Accessory Structures of the Skin
Exposed shaft
of hair
Hair shaft
Boundary
between hair
shaft and
hair root
Hair
root
Sebaceous
gland
Arrector
pili muscle
Connective
tissue
sheath
Hair bulb
Hair papilla
a A diagrammatic view of
a single hair follicle.
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Figure 4.9b Accessory Structures of the Skin
Hair follicle,
cross section
Arrector pili
muscle
Epidermis
Sebaceous
gland
Dermis
Hair
Subcutaneous
adipose tissue
Cortex
Hair bulb
Medulla
Hair papilla
Scalp, sectional view
LM × 66
b A light micrograph showing the
sectional appearance of the skin of
the scalp. Note the abundance of hair
follicles and the way they extend into
the dermis and hypodermis.
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Figure 4.10a Hair Follicles
Hair
Hair Structure
The cortex contains thick layers The cuticle, although
of the hair contains a
of hard keratin, which give the thin, is very tough, and
flexible soft keratin. hair its stiffness.
it contains hard keratin.
The medulla, or core,
Sebaceous
gland
Arrector
pili muscle
Connective
tissue sheath
Root hair
plexus
a A longitudinal section and a cross section through a hair follicle
© 2015 Pearson Education, Inc.
Hair follicle structures
Figure 4.15a Structure of a Nail
Direction
of growth
Free edge
Lateral
nail fold
Nail
Lunula
Eponychium
Proximal
nail fold
a View from the surface
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Figure 4.12 A Classification
of Exocrine Glands in the Skin
Exocrine Glands
consist of
• Assist in thermoregulation
• Excrete wastes
• Lubricate epidermis
Sweat Glands
Sebaceous Glands
• Secrete oily lipid (sebum) that
coats hair shaft and epidermis
• Provide lubrication and
antibacterial action
Sebaceous Glands
Sebaceous Follicles
Secrete into hair follicles
Secrete onto skin surface
• Produce watery solution by
merocrine secretion
• Flush epidermal surface
• Perform other special functions
Apocrine Sweat Glands
• Limited distribution
(axillae, groin, nipples)
• Produce a viscous
secretion of complex
composition
• Possible function in
communication
• Strongly influenced by
hormones
• Merocrine secretion
mechanism
• Widespread
• Produce thin secretions,
mostly water
• Controlled primarily by
nervous system
• Important in thermoregulation
and excretion
• Some antibacterial action
special apocrine glands
Ceruminous Glands Mammary Glands
Secrete waxy cerumen
into external ear canal
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Merocrine Sweat Glands
Apocrine glands
specialized for milk
production
Figure 4.13 Sebaceous
Glands and Follicles (2 of 2)
Lumen (hair
removed)
Wall of
hair follicle
Basal lamina
Discharge of
sebum
Lumen
Breakdown of
cell membranes
Mitosis and
growth
Sebaceous
gland
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Germinative
cells
LM × 150
Figure 4.14a Sweat
Glands
Myoepithelial cell
Connective
tissue of dermis
Sweat pore
Duct
Apocrine
gland cells
Lumen
LM × 440
a
Apocrine sweat glands
are found in the axillae
(armpits), groin, and
nipples. They produce a
thick, potentially
odorous fluid.
© 2015 Pearson Education, Inc.
Duct of
apocrine
sweat gland
Sectional plane
through apocrine
sweat gland
Cross section
of merocrine
sweat gland
Which of the following glands produces the
type of sweat that is involved in cooling the
body during and after a vigorous game of
basketball?
a) ceruminous glands
b) sebaceous glands
c) merocrine sweat glands
d) apocrine sweat glands
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Which type of integumentary gland is involved
in acne formation?
a) apocrine glands
b) merocrine glands
c) sebaceous glands
d) ceruminous glands
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Figure 4.16 The
Skin during the Aging Process
Fewer Active
Melanocytes
• Pale skin
• Reduced
tolerance for
sun exposure
Fewer Active
Follicles
Thinner, sparse
hairs
Reduced Skin
Repair
Skin repairs
proceed
more slowly.
Decreased
Immunity
The number of dendritic cells
decreases to about 50 percent
of levels seen at maturity
(roughly age 21).
Thin Epidermis
• Slow repairs
• Decreased vitamin
D production
• Reduced number
of Langerhans cells
Reduced Sweat
Gland Activity
Tendency to
overheat
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Changes in Distribution
of Fat and Hair
Dry
Epidermis
Due to reductions in
sex hormone levels
Reduction in
sebaceous and
sweat gland
activity
Reduced Blood Supply
Thin Dermis
• Slow healing
• Reduced ability to
lose heat
Sagging and
wrinkling
due to
fiber loss
Watch “Skin” segment National Geographic youtube 5min 40sec
Which of the following is a primary function of
the integument?
a. thermoregulation
b. absorption
c. storage of calcium reserves
d. locomotion
Thick skin and thin skin refer to differences
in:
a) Papillary layer
c) Dermis
b) Hypodermis
d) Epidermis
Layer of skin that contains bundles of
collagen fibers & elastin for strength:
a) Papillary layer
c) Reticular layer
b) St. corneum
d) St. basale
Fingerprint ridge patterns on the fingertips are
unique to each person and are determined
by:
a. genetics.
b. epidermal ridges.
c. dermal papillae.
d. all of the above
3. Epidermal ridges:
a) Are at the surface of epidermis only
b) Cause ridge patterns on surface of skin
c) Connect statum spinosum with stratum
lucidum
d) Are determined by environmental factors
The subcutaneous layer:
a. helps reduce heat loss in infants and
small children.
b. is an integral part of the integument.
c. is evenly distributed throughout the body,
and between sexes.
d. consists of dense regular connective
tissue.