Transcript Chapter 5 Integumentary system.ppt

5
The
Integumentary
System
PowerPoint® Lecture Presentations prepared by
Alexander G. Cheroske
Mesa Community College at Red Mountain
© 2011 Pearson Education, Inc.
Section 1: Skin Functional Anatomy
• Integumentary system
• Most accessible organ system
• Can be referred to as skin or integument
• 16% of total body weight
• 1.5–2 m2 in area
• Body’s first line of defense against environment
• Has two major components
1. Cutaneous membrane
2. Accessory structures
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Section 1: Skin Functional Anatomy
• Cutaneous membrane layers
1. Epidermis (epi, above)
• Stratified squamous epithelium
2. Dermis
• Papillary layer (areolar connective tissue)
• Reticular layer (dense irregular connective tissue)
• Hypodermis (subcutaneous layer)
•
Not part of integument
•
Separates integument from deep fascia
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Section 1: Skin Functional Anatomy
• Accessory structures
• Hair shaft and follicle
• Sweat gland
• Tactile and lamellated corpuscles
• Sebaceous gland
• Arrector pili muscle
• Nerve fibers
• Cutaneous plexus (network of blood vessels)
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The structure of the skin, or integument, which consists of the cutaneous membrane and accessory structures
Accessory Structures
Cutaneous Membrane
The epidermis (epi, above)
consists of a stratified
squamous epithelium.
Hair shaft
Pore of sweat
gland duct
Papillary layer
Tactile corpuscle
Dermis
Reticular layer
Sebaceous gland
The dermis consists of a
papillary layer of areolar
tissue and a reticular layer of
dense irregular connective
tissue.
Arrector pili muscle
Sweat gland duct
Hair follicle
Lamellated corpuscle
The hypodermis
(subcutaneous layer or
superficial fascia) separates
the integument from the
fascia around deeper organs.
Note that this tissue layer is
not part of the integument.
Nerve fibers
Sweat gland
Artery
Fat
Vein
The network of
arteries and veins
connected to smaller
vessels servicing the
tissues of the integumentary system is the
cutaneous plexus.
Figure 5 Section 1
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Layers of the Integument (Figure 6.1)
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Hair shaft
Sweat pore
Epidermis
Epidermal ridge
Dermal papilla
Papillary
layer
Integument
Arrector pili muscle
Sebaceous (oil) gland
Dermis
Sweat gland duct
Reticular
layer
Merocrine sweat gland
Vein
Artery
Subcutaneous
layer
Adipose connective tissue
Hair follicle
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Tactile
(sensory)
receptors
Areolar
Sensory
connective tissue nerve fiber
Figure 5 Section 1
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Figure 5 Section 1
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Module 5.1: Epidermis
• Epidermis
• Dominated by the most abundant epithelial cells
(keratinocytes)
• Continuously produced in the deepest layers and
shed at exposed surface
• Form several layers or strata
• Deep layers form epidermal ridges
• Bind to dermal papilla (papilla, nipple-shaped mound) of
dermis
• Most of body covered with four strata (thin skin)
• Palms of hands and soles of feet have five strata
(thick skin)
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The spatial relationship between epidermal ridges and
dermal papillae
Epidermis
Epidermal
ridge
Dermal
papilla
Dermis
Figure 5.1
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1
The structures of thin skin
and thick skin
Epidermis
Dermis
Thin skin LM x 225
Dermal papilla
Epidermal ridge
Thick skin
LM x 225
Figure 5.1
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– 3
• The epithelium of the integument
• Termed epidermis
• Keratinized, stratified squamous epithelium
• Consists of specific layers, or strata
• Layers from deep to superficial: baby spits green leftover corn
• stratum basale – bottom layer
• stratum spinosum
• stratum granulosum
• stratum lucidum- only where the skin is especially thick, such as the
soles of the feet and the palms of the hands-
• stratum corneum
• first three layers with living keratinocytes
• most superficial two layers with dead keratinocytes
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Module 5.1: Epidermis
• Layers of the epidermis
1. Stratum corneum (cornum, horn)
•
Outermost protective layer
•
15–30 layers of keratinized cells (filled with
keratin)
•
All dead cells attached with desmosomes
•
Remain in stratum corneum ~2 weeks before shed
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Module 5.1: Epidermis
• Layers of the epidermis (continued)
2. Stratum lucidum (“clear layer”)
•
Separates stratum corneum from underlying layers
•
Flattened dead cells filled with keratin and
keratohyalin
•
Absent in thin skin
3. Stratum granulosum (“grainy layer”)
•
3–5 layers of keratinocytes
•
Living cells that have stopped dividing and started
making keratin and keratohyalin
•
As protein fibers develop, membranes become less
permeable
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Module 5.1: Epidermis
• Layers of the epidermis (continued)
4. Stratum spinosum (“spiny layer”)
•
8–10 layers of live keratinocytes bound by desmosomes
•
•
Cells look spiny in histological sections
Dendritic cells (immune system cells) also found here
•
Defend against pathogens and superficial cancers
5. Stratum basale
•
Basal cells (stem cells) attached to basal lamina with
hemidesmosomes
•
•
Actively dividing to replace cells lost on superficial layers
Merkel cells (touch receptors) also found here
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Layers of the epidermis
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
Papillary layer of dermis
LM x 470
Figure 5.1
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Epidermal Strata (Figure 6.2)
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Dead keratinocytes
Stratum corneum
Sweat gland duct
Sweat gland duct
Stratum lucidum
Stratum granulosum
Living keratinocyte
Stratum spinosum
Melanocyte
Epidermal dendritic cell
Stratum basale
Basement membrane
Dermis
Tactile cell
LM 25x
Sensory nerve ending
(a)
(b)
a: © Ed Reschke/Peter Arnold Images
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Variations in the epidermis
• Variations between different body regions
• Variations between individuals
• Variations in thickness, color, and skin markings
• Thick versus thin skin
• Thick skin
• on the palms of hands, soles of feet, and surfaces of fingers
and toes
• has all five layers of epidermal strata
• has sweat glands
• has no hair follicles or sebaceous glands
• from 0.4 to 0.6 mm thick
• Thin skin
• covers most of the body
• lacks a stratum lucidum
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Thick Skin and Thin Skin (Figure 6.3)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Stratum corneum
Epidermis
Stratum granulosum
Stratum spinosum
Stratum
corneum
Epidermis
Stratum basale
LM 75x
LM 40x
Dermis
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
(a) Thick skin
(b) Thin skin
a: © Carolina Biological Supply Company/Phototake b: © Carolina Biological Supply Company/Phototake
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Module 5.2: Skin color
• Skin color
• Influenced by:
• Presence of pigments
• Primarily melanin and carotene
• Degree of dermal circulation
• Thickness and degree of keratinization of epidermis
• UV radiation, but genetically programmed
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Module 5.2: Skin color
• Melanocytes
• Manufacture melanin from amino acid tyrosine
• Package melanin in vesicles (melanosomes)
• Transferred to keratinocytes and maintained until fusion
with lysosomes
• Occurs in stratum basale and spinosum in lightskinned people
• Transfer of larger melanosomes into stratum
granulosum as well for dark-skinned people
• Differences in skin pigmentation is not number of
melanocytes but varying cell synthetic activities
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Coloring from melanin
Pigment produced and stored
in melanocytes
Occurs in black, brown, tan,
yellow-brown shades
Transferred to keratinocytes
in stratum basale
Amount in skin varies
according to heredity and
light exposure
UV light stimulating
melanin production
All people with same number
of melanocytes
Activity and color varying
among individuals
darker skinned producing
more and darker colored
melanin
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The epidermal cells, structures, and pigments
that influence skin coloration
Melanocytes
in stratum
basale
Melanin
pigment
Basal lamina
Thin skin
LM x 400
Melanosomes travel within the processes of melanocytes and are
transferred intact to keratinocytes. The transfer of pigmentation
colors the keratinocyte temporarily, until the melanosomes are
destroyed by fusion with lysosomes. In individuals with pale skin,
this transfer occurs in the stratum basale and stratum spinosum,
and the cells of more superfical layers lose their pigmentation. In
dark-skinned people, the melanosomes are larger, and the transfer
may occur in the stratum granulosum as well; skin pigmentation is
thus darker and more persistent.
Keratinocyte
Melanin is a brown,
yellow-brown, or black
pigment produced by
melanocytes.
Carotene (KAR-uh-tēn) is
an orange-yellow pigment
that normally accumulates
in epidermal cells. It is
most apparent in cells of
the stratum corneum of
light-skinned individuals,
but it also accumulates in
fatty tissues in the deep
dermis and hypodermis.
Carotene is found in a
variety of orange
vegetables.
The melanocytes are
located in stratum
basale, squeezed
between or deep to the
epithelial cells.
Melanocytes manufacture melanin from the
amino acid tyrosine,
and package it in
intracellular vesicles
called melanosomes.
The color of one’s skin is
genetically programmed.
However, increased
pigmentation, or tanning,
can result in response to
ultraviolet (UV) radiation.
Basal lamina
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Figure 5.2
1
Module 5.2: Skin color
• Carotene
• Orange-yellow pigment
• Accumulates in epidermis and fatty tissues of
hypodermis
• Found in variety of orange vegetables
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Module 5.2: Skin color
• Blood supply
• Red coloration from red blood cells with red
hemoglobin pigment
• Hemoglobin color varies with amount of oxygen
binding
• More oxygen: bright red
• Less oxygen: dark red
• Appears blue (cyanosis) seen from surface in thin
skinned areas (lips, under nails)
• Dilation (enlarging) or constriction of dermal blood
vessels also affects observed skin coloration
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The location of the papillary plexus, a network of capillaries
that affects skin color
Hair
Capillary
loop of
papillary
plexus
The papillary
layer of the skin
contains the
papillary plexus,
a network of
capillaries that
provides oxygen
and nutrients to
the dermis and
epidermis.
Papillary
layer
Cutaneous
plexus
Figure 5.2
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Variations in the epidermis
• Nevus
a mole
• Harmless overgrowth of melanin forming cells
• Rarely may become malignant- look for changes
• Freckles
• Yellowish or brown spots
• Represent localized areas of increased melanocyte activity
• Degree of pigmentation based on sun exposure and heredity
• Hemangioma
• Skin discoloration due to benign blood vessel tumor
• Capillary hemangiomas strawberry-colored birthmarks
• appear in skin as bright red to deep purple nodules
usually
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Inc. present
at birth and disappear in childhood
Variations in the
epidermis
• Ridge patterns of the
skin
• Small conical pegs in thin skin
• Complex arches and whorls on
finger, palms, soles, and toes
• called friction ridges
• formed from large folds and
valleys of dermis and
epidermis
• help increase friction on
contact
• each individual with a unique
pattern of friction ridges
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Composition of the Integument: Epidermis
Clinical View: UV Radiation, Sunscreens,
and Sunless Tanners
• Ultraviolet radiation is believed to cause skin cancer.
• UVA between 320 and 400 nm
• UVB between 290 and 320 nm
• Sunscreens block UVA and UVB rays.
• Protect the skin if used correctly
• Need high enough SPF (sun protection factor)
• Sunless tanners create tanned skin without UV light
exposure.
• Offer no protection against UV rays
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Module 5.2: Skin color
• Skin cancers (most common types of cancer)
• Types
• Basal cell carcinoma
• Most common skin cancer
• Originates in stratum basale in response to UV
radiation
• Virtually no metastasis and most people survive
• Malignant melanoma
• Cancerous melanocytes
• Commonly metastasize through lymphatic system
• Detected early, 5-year survival is 99%
• Not detected until metastasis, 5-year survival is 14%
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Figure 5.2
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Figure 5.2
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4
Layers of the Dermis (Figure 6.6)
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Epidermal ridges
Dermal papillae
Epidermis
Papillary layer
Dermis
Reticular layer
Tactile (sensory) receptor
Artery
Vein
Subcutaneous layer
Areolar connective tissue
Adipose connective tissue
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Module 5.3: Dermis and hypodermis
• Dermis
• Between epidermis and hypodermis
• Contains two fiber types
1. Collagen (strong and resists stretching)
2. Elastin (permits stretching and recoil)
• Reduced due to aging, hormonal changes, UV
radiation
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Module 5.3: Dermis and hypodermis
• Dermis
• Has two layers
1. Papillary layer
•
Named for dermal papillae
•
Consists of areolar tissue
•
Contains:
•
Capillaries
•
Lymphatic capillaries
•
Sensory neurons
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Module 5.3: Dermis and hypodermis
• Dermis
• Has two layers (continued)
2. Reticular layer
•
•
Meshwork of dense irregular connective tissue
•
Collagen fibers (extend into papillary layer and
hypodermis)
•
Elastin fibers
Contains similar structures as papillary layer but also
sweat glands and hair follicles
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Clinical View:
Tattoos
• Permanent
images
produced on
integument
• Dye injected
into dermis
• Becomes
permanent
part of dermis
layer
• Usually
impossible to
completely
remove a
tattoo
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Education, Inc.
• Dermis with extensive nerve fibers
• Sensory nerve fibers
• detect pressure, vibration, and cold
• Motor nerve fibers
• control blood flow and gland secretions
• Dermal blood vessels
• Supply nutrients to epidermis and dermis
• Vasoconstriction blood vessel diameters narrowed
• blood shunted from periphery toward deeper structures
• occurring when trying to conserve heat
• look pale when exposed to cold
• Vasodilation blood vessel diameter increased
• more blood close to body surface
• occurs when needing to loose heat
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Module 5.3: Dermis and hypodermis
• Hypodermis
• Separates skin from deeper structures
• Stabilizes skin to underlying tissues
• Allows independent movement
• Dominated by adipose tissue
• Storage of energy
• Accumulation in men: neck, arms, lower back,
buttocks
• Accumulation in women: breasts, buttocks, hips,
thighs
• For both adult sexes: few cells on back of hands and
surfaces of feet, more in abdominal region
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The structures of the dermis and the deeper hypodermis
Epidermal
ridges
Dermal
papillae
Papillary
layer
Reticular
layer
Papillary
plexus
Cutaneous
plexus
Adipocytes
Reticular layer of dermis
SEM x 1500
Hypodermis
SEM x 250
Figure 5.3
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– 3
Integument
Layers
and the
Subcutaneous
Layer
(Table 6.1)
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Module 5.3: Dermis and hypodermis
• Skin sensory receptors
• Epidermis
• Merkel cells in deep layers
• Monitored by tactile discs
• Sensory neuron extensions for pain and
temperature
• Dermis
• Similar to epidermis but more specialized
receptors as well
• Light touch (tactile corpuscles in dermal papillae)
• Deep pressure/vibration (lamellated corpuscles in
reticular layer)
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The sensory receptors in the integument
Merkel cell
Tactile disc
Free nerve
endings of
sensory neurons
Tactile corpuscle
Lamellated
(pacinian) corpuscle
Figure 5.3
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Composition of the Integument: Dermis
Lines of cleavage, stretch marks, and wrinkles
• Collagen and elastic fibers oriented in parallel bundles
– Alignment result of applied stress during routine movement
– Bundles functioning to resist stress
– Orientation indicated by lines of cleavage (tension lines)
– Important consideration for surgery
• incisions parallel
– more likely to heal quickly
• incisions perpendicular to cleavage lines
– more likely to open due to cut elastic fibers
• Sometimes skin stretched beyond its capabilities
• some collagen fibers torn
• stretch marks, termed striae, occur
• Flexibility and thickness of dermis
• diminished by UV light and aging
• may cause sagging or wrinkled skin
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Lines of Cleavage (Figure 6.7)
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An incision
perpendicular
to cleavage lines may
gape and delay healing.
An incision parallel to
cleavage lines is more
likely to heal quickly and
not gape open.
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Section 2: Accessory Organs of the Skin
• Accessory structures
• Hair follicles
• Produce hairs that protect skull
• Produce hairs that provide delicate touch sensations
• Exocrine glands
• Assist in thermoregulation
• Excrete wastes
• Lubricate epidermis
• Nails
• Protect and support tips of fingers and toes
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Module 5.4: Hair
•
Hair
•
•
Found over most of body except palms of hands,
soles of feet, sides of fingers/toes, lips, and external
genitalia
Body has about 2.5 million hairs
•
•
•
75% on body (not head)
Nonliving structures produced by hair follicles
Two types
1. Terminal hairs (large, coarse, darkly pigmented hairs
such as on head or armpits)
2. Vellus hairs (smaller, shorter, delicate on general
body surface)
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Module 5.4: Hair
• Hair follicle
• Forms a single hair
• Composed of epithelial and connective tissues
• Layered structure (from innermost to outermost)
• Internal root sheath (surrounds hair root; deeper only)
• External root sheath (entire length of follicle)
• Glassy membrane (thick, clear basal lamina)
• Connective tissue sheath
• Base has hair bulb (epithelial cap) and hair papilla
(peg of connective tissue with blood vessels and
nerves)
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A cross-section through a hair follicle
Hair Structure
Medulla (core)
Cortex
Cuticle
Hair Follicle Structure
Internal root sheath
External root sheath
Glassy membrane
Connective tissue sheath
Figure 5.4
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Module 5.4: Hair
• Hair layers
• Cuticle (outermost layer made of keratin)
• Cortex (middle layer with hard keratin for
stiffness)
• Medulla (core with flexible soft keratin)
• Hair regions
• Hair shaft (exposed but extends into follicle)
• Hair root (anchoring portion where growth
occurs)
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The structure of a hair follicle
Sebaceous gland
Hair shaft
Hair root
Connective tissue sheath
Root hair plexus
Arrector pili
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Figure 5.4
1
Module 5.4: Hair
• Accessory hair structures
• Root hair plexus
• Sensory nerves surrounding base of follicle
• Arrector pili muscle
• Smooth muscle that pulls on follicle causing hair
to stand erect (goosebumps)
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Module 5.4: Hair
• Hair growth cycle
• Active phase (hair grows 2–5 years at ~0.33
mm/day)
• Variation in growth rate and duration of cycle yield
differences in length of uncut hair
• Follicle regresses and enters resting phase
• Hair loses attachment and becomes club hair
• Club hair shed as follicle reactivates
• Replacement hair growth begins
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The hair growth cycle
The follicle then
begins to undergo
regression and
transitions to the
resting phase.
The active phase lasts
2-5 years. During the
active phase, the hair
grows continuously at a
rate of approximately 0.33
mm/day.
During the resting
phase the hair loses
its attachment to the
follicle and becomes a
club hair.
When follicle
reactivation occurs,
the club hair is
shed and the hair
matrix begins
producing a
replacement hair.
Figure 5.4
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Module 5.4: Hair
• Hair color
• Differences in structure and variation in
pigments produced in melanocytes at hair
papilla
• Different forms of melanin for different hair colors
• Pigment production decreases with age
• White hair lacks pigment and has air bubbles in
the medulla
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Module 5.5: Sebaceous glands and sweat
glands
• Sebaceous glands (oil glands)
• Holocrine glands that discharge an oily lipid
secretion
• Simple branched alveolar glands that secrete
onto one hair follicle
• Contractions of arrector pili muscle cause
release of sebum onto follicle and skin surface
• Sebum
• Mixture of triglycerides, cholesterol, proteins, and
electrolytes
• Lubricates hair shaft and is antimicrobial
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The structure and function of sebaceous glands
Sebaceous Glands
Sebaceous glands secrete sebum (SĒ-bum), which
coats the hair shaft and surrounding epidermal
surfaces. Sebum provides lubrication and keeps the
hair shaft from becoming dry and brittle. It also has
antibacterial properties.
Typical Sebaceous Glands
Sebaceous Follicles
Secrete into hair follicles
Secrete onto skin surface;
located on the face, back,
chest, nipples, and external
genitalia
Sebaceous gland
Lumen
(hair removed)
Wall of hair follicle
Basal lamina
Discharge of
sebum
Lumen
Breakdown of
cell membranes
Mitosis and
growth
Germinative
cells
Figure 5.5
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1
Module 5.5: Sebaceous glands and sweat
glands
• Sweat glands
• Produce watery secretion by merocrine
secretion
• Myoepithelial cells (myo-, muscle)
• Squeeze gland to discharge secretion
• Function to wash epidermal surface
• Two types
1. Apocrine sweat glands
2. Merocrine sweat glands
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Module 5.5: Sebaceous glands and sweat
glands
• Apocrine sweat glands
• Limited distribution (axillae, groin, nipples)
• Produce viscous secretion with complex
composition
• Possible function in olfactory communication
• Strongly influenced by hormones
• Include ceruminous glands and mammary
glands
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Module 5.5: Sebaceous glands and sweat
glands
• Merocrine sweat glands
• Found in most areas of skin
• Produce watery secretions with electrolytes
• Controlled primarily by nervous system
• Important in thermoregulation and excretion
• Some antibacterial action
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Derived from Epidermis
• Nails, hair, exocrine
glands derived from
epidermal epithelium
•
Known as epidermal
derivatives
•
Formed from portions of
epidermis invaginated into
the dermis
• Structure of nails
•
Scalelike modifications of
the stratum corneum
•
Form on the dorsal edges
of fingers and toes
•
Protect the distal tips of
the
digitsInc.
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Education,
Module 5.6: Nails
• Protect exposed dorsal surfaces of tips of fingers
and toes
• Help limit distortion of digits under physical stress
• Are composed of dead cells packed with keratin
• Can be affected by conditions that alter body
metabolism
• Can be used diagnostically
• Examples:
• Nails pitted and distorted: psoriasis
• Concave nails: some blood disorders
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Clinical View: Nail Disorders
• Changes in nails sometimes clinically significant
• Brittle nails prone to vertical splitting and separation of nail
plate layers
• Ingrown nails with edge of nail digging into skin
• Onchomycosis, a fungal infection
• Yellow nail syndrome when growth and thickening slows
• may be a sign of respiratory disease
• Spoon nails, nail malformation where outer surface of nails are
concave
• sign of iron deficiency
• Beau’s lines running horizontally across nail
• indicate temporarily interference with nail growth
• Vertical ridging
• common and usually harmless
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• Structure of nails
•
Distal whitish free edge (no
underlying capillaries)
•
Pinkish nail body
(underlying capillaries)
•
nail root (part embedded
in the skin)
•
nail bed Layer of living
epidermis covered by nail
body
•
nail matrix- Actively
growing part of nail at
proximal end of nail body
•
Lunula Whitish semilunar
area on proximal end of
nail body
•
Cuticle Narrow band of
epidermis
margin of
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The common landmarks of nail structure
The body covers
an area of
epidermis called
the nail bed.
Nail body
Lateral nail groove
Lateral nail fold
Direction
of growth
Free edge
of nail body
Near the root, the dermal blood vessels may
be obscured, leaving a
pale crescent known as
the lunula (LOO-nu-la;
luna, moon).
Proximal nail fold
Eponychium
Phalanx
(bone of fingertip)
Underlying blood vessels
give the nail its
characteristic pink color.
A portion of the stratum corneum
of the nail root extends over the
exposed nail, forming the
eponychium (ep-ō-NIK-ē-um;
epi, over; onyx, nail), or cuticle.
Proximal nail fold
Lunula Nail body
Nail production occurs at
the nail root, an epidermal
fold not visible from the
surface. The deepest
portion of the nail root lies
very close to the bone of
the fingertip.
Epidermis Dermis
The free edge of the
nail—the distal
portion that
continues past the
nail bed—extends
over the
hyponychium
(hī-pō-NIK-ē-um), an
area of thickened
stratum corneum.
Phalanx
Figure 5.6
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1
Module 5.7 : Age-related changes
• Age-related changes in skin
• Fewer melanocytes
• Thinning, drier epidermis
• Diminished immune response
• Thinning dermis
• Decreased participation
• Age-related changes in skin (continued)
• Reduced blood supply
• Slower skin repair
• Fewer active follicles
• Altered hair and fat distribution
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Module 5.8: Endocrine functions and the skin
• Hormones coordinate integumentary system
function with other systems
• Steroid hormones (glucocorticoids)
• Loosen intercellular connections and reduce epidermis
effectiveness as a barrier to infection
• Thyroid hormones
• Maintain normal blood flow to papillary plexus
• Sex hormones
• Increase epidermal thickness
• Accelerate wound healing
• Increase number of dendritic cells protecting against
cancer cells and pathogens
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Module 5.8: Endocrine functions and the skin
• Hormones coordinate integumentary system
function with other systems (continued)
• Epidermal growth factor (EGF)
•
Peptide that has widespread effects on epithelia
•
Produced by salivary glands and glands in duodenum
•
Functions
• Promote cell division in stratum basale and spinosum
• Accelerate production of keratin
• Stimulate epidermal development and repair
• Stimulate synthesis and secretion in glands
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Module 5.8: Endocrine functions and the skin
• Hormones coordinate integumentary system
function with other systems (continued)
• Growth hormone
• Stimulates fibroblast activity and collagen
production
• Stimulates germinal cell division
• Thickens epidermis
• Promotes wound repair
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Module 5.8: Endocrine functions and the skin
• Vitamin D3
• Sources
• Sunlight
• UV radiation causes epidermal cells of stratum spinosum
and basale to convert steroid to cholecalciferol
• Liver creates intermediate product then converted to
calcitriol by kidneys
• Calcitriol allows calcium and phosphate absorption in
intestine
• Diet
• Naturally from fish, fish oils, and shellfish
• From fortified food products
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Module 5.8: Endocrine functions and the skin
• Rickets
• Condition resulting in poorly mineralized bones
• In children, develops from not enough sunlight or
not enough dietary cholecalciferol
• Uncommon in United States
• In elderly, skin production of cholecalciferol
decreases by 75%
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Module 5.9 CLINICAL MODULE: Skin repair
• Steps of regeneration after injury
1. Initial injury
•
Bleeding
•
Mast cells cause inflammation
2. After several hours
•
Blood clot (scab) forms
•
Macrophages patrol and phagocytize debris and
pathogens
•
Stratum basale cells rapidly divide and migrate to wound
•
Granulation tissue forms (blood clot, fibroblasts,
formation of extensive capillary network)
© 2011 Pearson Education, Inc.
The steps in the regeneration of the skin after injury
Initial Injury
Immediately after the
injury, mast cells in
the region trigger an
inflammatory
response.
After Several Hours
Bleeding
occurs at the
site of injury.
Epidermis
Dermis
The blood clot, or scab, that forms at the surface
temporarily restores the integrity of the epidermis and
restricts the entry of additional microorganisms into the
area. The scab is red due to the presence of trapped red
blood cells.
Macrophages patrol the
damaged area of the
dermis, phagocytizing
debris and pathogens.
Cells of the stratum
basale undergo rapid
divisions and begin to
migrate along the edges
of the wound in an
attempt to replace the
missing epidermal cells.
If the wound occupies an extensive area or involves a region
covered by thin skin, dermal repairs must be under way before
epithelial cells can cover the surface. Divisions by fibroblasts and
mesenchymal cells produce mobile cells that invade the deeper
areas of injury. Endothelial cells of damaged blood vessels also
begin to divide, and new capillaries grow in behind the
fibroblasts, enhancing circulation. The combination of blood clot,
fibroblasts, and an extensive capillary network is called
granulation tissue.
Figure 5.9
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1
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Module 5.9 CLINICAL MODULE: Skin repair
• Steps of regeneration after injury (continued)
3. After one week
•
Parts of blood clot dissolve
•
Fibroblasts create more collagen fibers and ground
substance
• Steps of regeneration after injury (continued)
4.After several weeks
• Scab sheds
• Epidermal repair completes
• Scar tissue created by fibroblasts raise up epithelium
• Replaces damaged accessory structures of skin
© 2011 Pearson Education, Inc.
The steps in the regeneration of the skin after injury
After One Week
After Several Weeks
Over time, deeper portions of the clot dissolve, and
the number of capillaries declines. Fibroblast
activity leads to the appearance of collagen fibers
and typical ground substance. The repairs do not
restore the integument to its original condition,
however, because the dermis will contain an
abnormally large number of collagen fibers and
relatively few blood vessels.
Fibroblasts
Severely damaged hair follicles, sebaceous
or sweat glands, muscle cells, and nerves
are seldom repaired, and they too are
replaced by fibrous tissue. The formation of
this rather inflexible, fibrous, noncellular
scar tissue completes the repair process
but fails to restore the tissue to its original
condition.
Scar
tissue
Figure 5.9
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3
– 4
Module 5.9 CLINICAL MODULE: Skin repair
• Keloid
• Raised thickened mass of scar tissue
• Grows into surrounding dermis
• Most often in dark-skinned adults
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