Transcript Skin and Body Membranes

Skin and Body
Membranes
Human Anatomy and Physiology
General Characteristics of
Body Membranes
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Cover surfaces of body/ line body cavities
Form protective and often lubricating sheets
around organs
2 major groups
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Epithelial
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Cutaneous/ Mucous/ Serous Membranes
Connective
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Synovial Membranes
Epithelial Membranes:
covering & lining membranes
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Cutaneous (skin)
Mucous (lines body cavities that open to
exterior)
Serous (lines body cavities closed to exterior)
Remember all include both epithelial tissue
AND an underlying layer of connective
tissue…so these membranes are actually
simple organs
Cutaneous Membrane
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Epidermis on outside
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Dermis under epidermis
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Stratified squamous
Keratinizing
Dense (fibrous)
connective tissue
Cutaneous membrane
is exposed to air so its
considered a “dry
membrane”
Mucous
Membranes
(mucosa)
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Lines body cavities
opening to outside:
respiratory/ digestive/
urinary/ reproductive
tracts
Epithelium resting on
loose connective tissue
“wet membranes”
Adapted for absorption
or secretion
Serous Membranes (serosa)
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Line body cavities that are
not exposed to outside
Simple squamous
epithelium resting on thin
areolar connective tissue
Occurs in pairs: parietal
and visceral
Peritoneum = abdominal
cavity
Pericardium = around
heart
Pleura = around lungs
Parietal layer lines the wall of ventral
body/ Visceral layer covers the outside
of the organ in that cavity
Connective Tissue
membranes: Synovial
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No epithelial cells
Soft areolar connective
tissue
Line fibrous capsules
surrounding joints
Cushion organs rubbing
against each other
Secrete lubricating fluid
Also line bursae
The Integumentary System
(your skin!)
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List 4 important functions of the
integumentary system, and explain how
these functions are accomplished.
Label a diagram of the skin recognizing the
following: epidermis, dermis (papillary and
reticular layers), hair and hair follicle,
sebaceous gland, and sweat gland
Describe the distribution and function of
sebaceous glands, sweat glands and hair
The Integumentary System
(continued)
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Name the factors that determine skin color
and describe the function of melanin
Describe syndromes/ infections/ allergic
reactions in skin
Differentiate first, second and third degree
burns
Explain the importance of the “rule of nines”
Summarize the characteristics of basal cell
carcinoma, squamous cell carcinoma and
malignant melanoma
What specifically is the
integumentary system?
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Cutaneous
membrane
All its derivatives:
 Sweat glands
 Oil glands
 Hair
 Nails
Functions of the Skin
Controls internal body temperature:
1.
1.
2.
2.
3.
Heat loss: activates sweat glands and allows
blood to flush into skin capillary beds so heat
can radiate from skin surface
Heat retention: not allowing blood to flush to skin
capillary beds
Aids in excretion of urea and uric acid:
perspiration by sweat glands
Synthesizes vitamin D: modified cholesterol
molecules in skin
Functions of Skin (cont.)
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Protects deeper tissue from
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Mechanical damage: physical barrier, keratin, fat
cells, pressure receptors to stimulate movement
Chemical damage: impermeable keratin,
chemoreceptors, nociceptors
Bacterial damage: skin secretions
Ultraviolet radiation: melanin
Thermal damage: thermoreceptors/ nociceptors
Desiccation: water proofing glycolipid and keratin
Integumentary system provides
a wealth of sensory data
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Receptors are classified by the following:
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Stimulus type
Location
Structural complexity
Classification by Stimulus
Type
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Mechanoreceptors—respond to touch, pressure,
vibration, stretch, and itch
Thermoreceptors—sensitive to changes in
temperature
Photoreceptors—respond to light energy (e.g.,
retina)
Chemoreceptors—respond to chemicals (e.g., smell,
taste, changes in blood chemistry)
Nociceptors—sensitive to pain-causing stimuli (e.g.
extreme heat or cold, excessive pressure,
inflammatory chemicals)
Classification by Location
1.Exteroceptors
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Respond to stimuli arising outside the body
Receptors in the skin for touch, pressure, pain, and temperature
Most special sense organs
2. Interoceptors (visceroceptors)
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Respond to stimuli arising in internal viscera and blood vessels
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Sensitive to chemical changes, tissue stretch, and temperature
changes
3. Proprioceptors
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Respond to stretch in skeletal muscles, tendons, joints, ligaments,
and connective tissue coverings of bones and muscles
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Inform the brain of one’s movements
Classification by Structural
Complexity
1. Complex receptors (special sense organs)
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Vision, hearing, equilibrium, smell, and taste
(Chapter 15)
2. Simple receptors for general senses:
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Tactile sensations (touch, pressure, stretch,
vibration), temperature, pain, and muscle sense
Unencapsulated (free) or encapsulated dendritic
endings
Unencapsulated Dendritic
Endings
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Thermoreceptors
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Cold receptors (10–40ºC); in superficial dermis
Heat receptors (32–48ºC); in deeper dermis
Nociceptors
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Respond to:
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Pinching
Chemicals from damaged tissue
Temperatures outside the range of thermoreceptors
Capsaicin
Light touch receptors
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Tactile (Merkel) discs
Hair follicle receptors
Table 13.1
Encapsulated Dendritic
Endings
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All are mechanoreceptors
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Meissner’s (tactile) corpuscles—discriminative touch
Pacinian (lamellated) corpuscles—deep pressure and
vibration
Ruffini endings—deep continuous pressure
Muscle spindles—muscle stretch
Golgi tendon organs—stretch in tendons
Joint kinesthetic receptors—stretch in articular
capsules
Table 13.1
Skin (Integument)
Consists of three major regions
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1.
2.
3.
Epidermis—superficial region
Dermis—middle region
Hypodermis (superficial fascia)—deepest region
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Subcutaneous layer deep to skin (not technically
part of skin)
Mostly adipose tissue
Epidermis
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Keratinized stratified squamous epithelium
Cells of epidermis
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Keratinocytes—produce fibrous protein keratin
Melanocytes
 10–25% of cells in lower epidermis
 Produce pigment melanin
Epidermal dendritic (Langerhans) cells—
macrophages that help activate immune system
Tactile (Merkel) cells—touch receptors
Keratin
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Fibrous protein that
helps give the
epidermis its protective
properties
Found not only in skin,
but also hair, nails,
claws, horns, scales,
shells, feathers, even
baleen plates of whales
Strong, waterproof,
contains sulfur
Melanocytes
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Spider-shaped cells
found in stratum basale.
Produce pigment
melanin which
accumulates in granules
called melanosomes
Melanosomes are taken
up by keratinocytes
where they accumulate
on the sunny side of the
nucleus
Layers of the Epidermis:
Stratum Basale (Basal Layer)
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Deepest epidermal layer firmly attached to
the dermis
Single row of stem cells
Also called stratum germinativum: cells
undergo rapid division
Journey from basal layer to surface
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Takes 25–45 days
(a)
Dermis
Stratum corneum
Most superficial layer; 20–30 layers of dead
cells represented only by flat membranous
sacs filled with keratin. Glycolipids in
extracellular space.
Stratum granulosum
Three to five layers of flattened cells,
organelles deteriorating; cytoplasm full of
lamellated granules (release lipids) and
keratohyaline granules.
Stratum spinosum
Several layers of keratinocytes unified by
desmosomes. Cells contain thick bundles of
intermediate filaments made of pre-keratin.
Stratum basale
Deepest epidermal layer; one row of actively
mitotic stem cells; some newly formed cells
become part of the more superficial layers.
See occasional melanocytes and epidermal
dendritic cells.
Figure 5.2a
Layers of the Epidermis:
Stratum Spinosum (Prickly
Layer)
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Cells contain a weblike system of
intermediate prekeratin filaments attached to
desmosomes
Abundant melanin granules and dendritic
cells
Stratum corneum
Most superficial layer; 20–30 layers of dead
cells represented only by flat membranous
sacs filled with keratin. Glycolipids in
extracellular space.
Stratum granulosum
Three to five layers of flattened cells,
organelles deteriorating; cytoplasm full of
lamellated granules (release lipids) and
keratohyaline granules.
Stratum spinosum
Several layers of keratinocytes unified by
desmosomes. Cells contain thick bundles of
intermediate filaments made of pre-keratin.
Stratum basale
Deepest epidermal layer; one row of actively
mitotic stem cells; some newly formed cells
become part of the more superficial layers. See
occasional melanocytes and epidermal
dendritic cells.
Desmosomes
Melanin granule
Melanocyte
(b)
Keratinocytes
Dermis
Sensory
nerve ending Epidermal
Tactile
dendritic cell
(Merkel) cell
Figure 5.2b
Layers of the Epidermis:
Stratum Granulosum (Granular
Layer)
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Thin; three to five cell layers in which the
cells flatten
Keratohyaline and lamellated granules
accumulate
(a)
Dermis
Stratum corneum
Most superficial layer; 20–30 layers of dead
cells represented only by flat membranous
sacs filled with keratin. Glycolipids in
extracellular space.
Stratum granulosum
Three to five layers of flattened cells,
organelles deteriorating; cytoplasm full of
lamellated granules (release lipids) and
keratohyaline granules.
Stratum spinosum
Several layers of keratinocytes unified by
desmosomes. Cells contain thick bundles of
intermediate filaments made of pre-keratin.
Stratum basale
Deepest epidermal layer; one row of actively
mitotic stem cells; some newly formed cells
become part of the more superficial layers.
See occasional melanocytes and epidermal
dendritic cells.
Figure 5.2a
Layers of the Epidermis:
Stratum Lucidum (Clear Layer)
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In thick skin
Thin, transparent band superficial to the
stratum granulosum
A few rows of flat, dead keratinocytes
Layers of the Epidermis:
Stratum Corneum (Horny
Layer)
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20–30 rows of dead, flat, keratinized
membranous sacs
Three-quarters of the epidermal thickness
Functions
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Protects from abrasion and penetration
Waterproofs
Barrier against biological, chemical, and physical
assaults
Stratum corneum
Most superficial layer; 20–30 layers of dead
cells represented only by flat membranous
sacs filled with keratin. Glycolipids in
extracellular space.
Stratum granulosum
Three to five layers of flattened cells,
organelles deteriorating; cytoplasm full of
lamellated granules (release lipids) and
keratohyaline granules.
Stratum spinosum
Several layers of keratinocytes unified by
desmosomes. Cells contain thick bundles of
intermediate filaments made of pre-keratin.
Stratum basale
Deepest epidermal layer; one row of actively
mitotic stem cells; some newly formed cells
become part of the more superficial layers. See
occasional melanocytes and epidermal
dendritic cells.
Desmosomes
Melanin granule
Melanocyte
(b)
Keratinocytes
Dermis
Sensory
nerve ending Epidermal
Tactile
dendritic cell
(Merkel) cell
Figure 5.2b
Dermis
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Strong, flexible connective tissue
Cells include fibroblasts, macrophages, and
occasionally mast cells and white blood cells
Two layers:
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Papillary
Reticular
Hair shaft
Epidermis
Papillary
layer
Dermis
Reticular
layer
Hypodermis
(superficial fascia)
Nervous structures
• Sensory nerve fiber
• Pacinian corpuscle
• Hair follicle receptor
(root hair plexus)
Dermal papillae
Subpapillary
vascular plexus
Pore
Appendages
of skin
• Eccrine sweat
gland
• Arrector pili
muscle
• Sebaceous
(oil) gland
• Hair follicle
• Hair root
Cutaneous vascular
plexus
Adipose tissue
Figure 5.1
Layers of the Dermis: Papillary
Layer
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Papillary layer
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Areolar connective tissue with collagen and
elastic fibers and blood vessels
Dermal papillae contain:
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Capillary loops
Meissner’s corpuscles
Free nerve endings
Epidermal ridges lie atop deeper dermal papillary
ridges to form friction ridges of fingerprints
Friction ridges
Openings of
sweat gland ducts
(a)
Figure 5.4a
(b)
Figure 5.4b
Layers of the Dermis: Reticular
Layer
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Reticular layer
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~80% of the thickness of dermis
Collagen fibers provide strength and resiliency
Elastic fibers provide stretch-recoil properties
Collagen fibers arranged in bundles form
externally invisible cleavage (tension) lines
Incisions made parallel to cleavage lines heal
more readily
Skin Color
Three pigments contribute to skin color:
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1.
Melanin
Yellow to reddish-brown to black, responsible for dark
skin colors
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2.
Carotene
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3.
Produced in melanocytes; migrates to keratinocytes where it
forms “pigment shields” for nuclei
Freckles and pigmented moles
Local accumulations of melanin
Yellow to orange, most obvious in the palms and soles
Hemoglobin
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Responsible for the pinkish hue of skin
Erythema
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Redness of the skin
caused by
embarrassment, fever,
hypertension,
inflammation,
allergy…or even
massage, acne
medicine, waxing, lyme
disease
30-50% erythema of
unknown cause
Pallor or Blanching
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Caused by fear,
anger, certain
emotional stress
Often a symptom
of anemia or low
blood pressure
Raynaud’s
syndrome
Jaundice
Yellow cast
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Can be a result of a
liver disorder in which
yellow bile pigments,
bilirubin, accumulate in
the body
Also could be a result of
eating a lot of
carotene…carotenemia
Albinism
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Absence of
pigment in the
skin, hair and
eyes.
Melanocytes are
present but
melanin not
produced because
of missing or
disabled enzyme
Black and Blue marks
Bruising
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Bruise can also be
called a contusion
Where blood has
escaped from the
circulation and clotted
beneath the skin
Mild Hematoma
Cyanosis
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When hemoglobin is
poorly oxygenated both
the blood and often the
skin appear blue
Skin become cyanotic
during heart failure and
severe respiratory
disorders
Not as evident in
darker skinned people
Blue Fugates of
Troublesome Creek, Kentucky
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Genetic Disorder that
was amplified in a small
Appalachain community
from a French
descendant
Form of hemoglobin,
methemoglobin cannot
be recycled back into
hemoglobin because of
an enzyme deficiency
Part 2 Skin Appendages
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Compare the structure and locations of sweat
and oil glands and their secretions.
Compare and contrast eccrine and apocrine
glands.
List the parts of a hair follicle. Describe
functional relationship of arrector pili muscles to
the hair follicle.
Name the regions of a hair and explain the
basis of hair color.
Describe the structure of nails.
Sweat Glands
Two main types of sweat (sudoriferous)
glands
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1.
Eccrine (merocrine) sweat glands—abundant on
palms, soles, and forehead
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Sweat: 99% water, NaCl, vitamin C, antibodies,
dermcidin (microbe killing peptide), metabolic wastes
(urea, uric acid and ammonia)
pH from 4-6
Ducts connect to pores
Function in thermoregulation
Multicellular Exocrine
Glands
 Multicellular
exocrine glands are
composed of a duct and a secretory
unit
 Classified according to:
 Duct type (simple or compound)
 Structure of their secretory units
(tubular, alveolar, or
tubuloalveolar)
Tubular
secretory
structure
Simple duct structure
Compound duct structure
(duct does not branch)
(duct branches)
Simple tubular
Simple branched
tubular
Example
Example
Compound tubular
Intestinal glands
Stomach (gastric)
glands
Duodenal glands of small intestine
Example
Alveolar
secretory
structure
Simple
alveolar
Simple branched
alveolar
Compound alveolar
Example
Example
Example
No important
example in humans
Sebaceous (oil)
glands
Mammary glands
Surface epithelium
Duct
Compound
tubuloalveolar
Example
Salivary glands
Secretory epithelium
Figure 4.5
Modes of Secretion
 Merocrine
 Products
are secreted by
exocytosis (e.g., pancreas, sweat
and salivary glands)
 Holocrine
 Products are secreted by rupture
of gland cells (e.g., sebaceous
glands)
What type of Secretion
is each picture?
Eccrine Sweat Glands are also
called merocrine sweat glands
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Sweating is regulated by the sympathetic
division of the autonomic nervous system
Major role is to prevent overheating of body
Heat induced sweating begins on forehead
and spreads inferiorly over body
Emotionally induced sweating begins on
palms, soles and axillae then spreads to
other areas of body
Sweat pore
Eccrine
gland
Sebaceous
gland
Duct
Dermal connective
tissue
Secretory cells
(b) Photomicrograph of a
sectioned eccrine gland (220x)
Figure 5.5b
Sweat Glands (cont.)
2.
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Apocrine sweat glands—confined to axillary and
anogenital areas
 Sebum: sweat + fatty substances and proteins so
secretion is yellow or whitish
 Ducts connect to hair follicles
 Functional from puberty onward (as sexual scent
glands?)/ basis of body odor
 Also merocrine glands as opposed to other apocrine
glands (3rd type of gland not seen in humans)
Specialized apocrine glands
 Ceruminous glands—in external ear canal; secrete
cerumen…ear wax!
 Mammary glands
Sebaceous (Oil) Glands
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Widely distributed, large on face, neck and
upper chest
Most develop from hair follicles
Become active at puberty
Sebum
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Oily holocrine secretion
Bactericidal
Softens hair and skin
Sweat
pore
Dermal
connective
tissue
Sebaceous
gland
Sebaceous
gland duct
Eccrine
gland
Hair in
hair follicle
Secretory cells
(a) Photomicrograph of a sectioned
sebaceous gland (220x)
Figure 5.5a
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Whitehead: When a
sebaceous gland duct
is blocked by
accumulated sebum.
If sebum oxidezes and
dries: blackhead
Cradle Cap (seborrhea)
is from overactive
sebaceous glands
“pores” on face are
external outlet of hair
follicles, where
sebaceous glands
empty
What is
Acne?
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Acne is active
inflammation of
sebaceous lands
accompanied by
“pimples” which are
pustules or cysts on
skin
Acne is usually caused
by bacterial infection,
often staphylococcus.
Hair
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Functions in Humans
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Alerting the body to presence of insects on the skin
Guarding the scalp against physical trauma, heat
loss, and sunlight
As opposed to other mammal hair functions like
trapping body heat
Distribution
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Entire surface except palms, soles, lips, nipples,
and portions of external genitalia
Hair
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Consists of dead keratinized cells
Contains hard keratin; more durable than soft
keratin of skin (and doesn’t flake off)
Three layers: medulla, cortex and cuticle
Hair pigments: melanins (yellow, rust brown,
black) produced by melanocyctes at base of
hair follicle amd transferred to cortical cells
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Gray/white hair: decreased melanin production,
increased air bubbles in shaft
Red hair due to iron containing pigment
Follicle wall
Hair shaft
Arrector
pili
Sebaceous
gland
Hair root
• Connective tissue
root sheath
• Glassy membrane
• External epithelial
root sheath
• Internal epithelial
root sheath
Hair
• Cuticle
• Cortex
• Medulla
(a) Diagram of a cross section of
a hair within its follicle
What is the role of hair conditioners?
Hair bulb
Figure 5.6a
Follicle wall
• Connective tissue
root sheath
• Glassy membrane
• External epithelial
root sheath
• Internal epithelial
root sheath
Hair
Hair shaft
Arrector
pili
Sebaceous
gland
Hair root
• Cuticle
• Cortex
• Medulla
(b) Photomicrograph of a cross
section of a hair and hair
follicle (250x)
Hair bulb
Figure 5.6b
Hair Follicle
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Extends from the epidermal surface into
dermis
Two-layered wall: outer connective tissue root
sheath, inner epithelial root sheath
Hair bulb: expanded deep end
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Hair papilla of dermal tissue protrudes into the hair
bulb
Contains a knot of capillaries that provide nutrients
to growing hair
Hair Follicle
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Hair follicle receptor (root hair plexus)

Sensory nerve endings around each hair bulb
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Stimulated by bending a hair
Arrector pili
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Smooth muscle attached to follicle
Responsible for “goose bumps”
Hair shaft
Arrector
pili
Sebaceous
gland
Hair root
Hair bulb
Follicle wall
• Connective tissue root sheath
• Glassy membrane
• External epithelial root sheath
• Internal epithelial root sheath
Hair root
• Cuticle
• Cortex
• Medulla
Hair matrix
Hair papilla
Melanocyte
Subcutaneous adipose tissue
(c) Diagram of a longitudinal view of the expanded hair
bulb of the follicle, which encloses the matrix
Figure 5.6c
Follicle wall
• Connective
tissue root sheath
• Glassy membrane
• External epithelial
root sheath
• Internal epithelial
root sheath
Hair root
• Cuticle
• Cortex
• Medulla
Hair matrix
Hair papilla
Subcutaneous
adipose tissue
Hair shaft
Arrector
pili
Sebaceous
gland
Hair root
Hair bulb
(d) Photomicrograph of longitudinal view
of the hair bulb in the follicle (160x)
Figure 5.6d
Types of Hair
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Vellus—pale, fine body hair of children and
adult females
Terminal—coarse, long hair of eyebrows,
scalp, axillary, and pubic regions (and face
and neck of males)
Hair growth and density influenced by
nutrition, hormones and local blood flow (that
can be increased by physical irritation)
Hirsutism: excessive hairiness
(particularly in women)
May result in
an adrenal
gland or
ovarian tumor
that secretes
abnormally
large
amounts of
androgens.
Types of Hair

Hair Growth


Growth rate averages 2.5 mm per week
Each follicle goes through growth cycles:




Growth phase (weeks to years) followed by regressive
stage and resting phase (1–3 months)
Growth phase varies (6–10 years in scalp, 3–4 months
in eyebrows)
During regressive stage, hair falls out. After resting
phase, cycling starts again and new hair is formed to
replace one that fell out
Loose an average of 90 scalp hairs daily
Hair Thinning and Baldness


Alopecia—hair thinning in both sexes after age
40
True (frank) baldness
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Genetically determined and sex-influenced condition
Male pattern baldness is caused by follicular response
to DHT
Until recently, the only cure for male pattern baldness
was to inhibit testosterone production…problems with
this?
By accident, minoxidil to reduce HBP, also stimulates
hair regrowth
Structure of a Nail

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Scalelike modification of the epidermis on the
distal, dorsal surface of fingers and toes
Made of hard keratin
Each nail has free edge, body and proximal root
Nail matrix at proximal root; responsible for nail
growth
Normally appear pink/ region over thick nail
matrix looks like half moon (lunule)
Lateral
nail fold
Lunule
(a)
Free edge Body
of nail
of nail
Eponychium
(cuticle)
Nail bed
Proximal
nail fold
Root of nail
Nail
matrix
(b)
Hyponychium
Phalanx (bone of fingertip)
Figure 5.7
Nail Basics



Proximal and lateral
borders of nail are
overlapped by skin
folds called nail folds
Proximal nail fold is the
eponychium (aka:
cuticle)
Region beneath the
free edge of the nail
where dirt and debris
accumulate is the
hyponychium (quick)
Functions of the
Integumentary System
1.
Protection—three types of barriers
Chemical

Low pH secretions (acid mantle) and defensins retard
bacterial activity


Physical and Mechanical



Keratin and glycolipids block most water and watersoluble substances
Limited penetration of skin by lipid-soluble substances,
plant oleoresins (e.g., poison ivy), organic solvents,
salts of heavy metals, some drugs
Biological barriers

Dendritic cells, macrophages, and DNA
Functions of the
Integumentary System
Body temperature regulation
2.


~500 ml/day of routine insensible perspiration (at
normal body temperature)
At elevated temperature, dilation of dermal
vessels and increased sweat gland activity
(sensible perspirations) cool the body
Cutaneous sensations
3.

Temperature, touch, and pain
Functions of the
Integumentary System
Metabolic functions
4.


5.
6.
Synthesis of vitamin D precursor and
collagenase
Chemical conversion of carcinogens and some
hormones
Blood reservoir—up to 5% of body’s blood
volume
Excretion—nitrogenous wastes and salt in
sweat
Part Three: Homeostatic
Imbalances of Skin




Summarize the characteristics of three major
skin cancers
Explain why serious burns are life
threatening. Describe how to determine the
extent of a burn and differentiate first, second
and third degree burns.
Discuss various common homeostatic
imbalances from acne to psoriasis.
ID effects of tattoo on skin
Homeostatic Imbalances of
Skin: Infections & Allergies
Skin can develop more than 1000 different
conditions and ailments.
Objectives:
1. Describe cause of several common skin
disorders .
2. Summarize the characteristics of the three
major types of skin cancers.
3. Explain why serious burns are life
threatening. Describe how to determine the
extent of a burn and differentiate first,
second and third-degree burns.
Burns

When skin is burned, 2 life threatening
problems result:



body loses supply of fluids containing proteins
and electrolytes. Dehydration and electrolyte
imbalance can lead to kidney shut down and
circulatory shock (inadequate blood flow to body)
After 24 hours, infection is important
threat…leading cause of death in burn victims.
Rule of Nines: way to determine volume of
fluid lost by burns
Rule of Nines


Divides the body into
11 areas each
representing 9% of
total body area, with
genitals accounting
for remaining 1%
This is obviously only
an approximation
Classification of Burns

First Degree





Only the epidermis is
damaged
Red and swollen
Heals in 2-3 days
Sunburn
Second Degree



Injury to epidermis and
upper region of dermis
Red, painful, blisters
Care to protect from
infection

Third Degree





Destroys entire thickness
of skin
Full thickness burn
Appears blanched (graywhite) or blackened
Nerve endings are
destroyed/ not painful
Regeneration not
possible/ skin grafting
necessary
Skin Cancer



The single most common type of cancer in
humans
1 in 5 Americans will develop skin cancer
Most important risk factor: overexposure
ultraviolet radiation in sunlight




Damages DNA bases (pyrimidines: C and T)
UV light disables tumor suppressor gene: p53
Most skin neoplasms are benign and do not
metastasize. For example: a wart
There are three types of malignant skin
neoplasms
Basal Cell Carcinoma






Least malignant
Most common skin
cancer/ 80%
Skin cells no longer
honor boundary
between epidermis and
dermis/ cannot form
keratin
Shiny domed shaped
nodules
Slow growing
Surgically removed, full
cure in 99% cases
Squamous Cell Carcinoma






Lesion is scaly, reddened,
small and rounded that
gradually forms an ulcer
Arises from keratinocytes
Most often occurs on
scalp, ears, dorsum of
hands, lower lip
Grows rapidly
Sun induced
Chance of cure good if
caught & removed early
Malignant Melanoma





Cancer of melanocytes
Metastasizes rapidly (50%
survival rate if
metastasized)
Resistant to chemotherapy
Forms wherever there is
pigment, sometimes moles
ABCD(E) rule:
Asymmetry/ Border
irregular/ Colors/ Diameter
larger than 6mm/ elevation
above skin
Your epidermal cells scream for
sunscreen!



Sunscreens are currently
rated for their ability to
prevent sunburn but not
for their ability to protect
against DNA damage.
SPF: Sun Protection
Factor
Research = levels of
radiation not strong
enough to burn still
affect DNA


UVA (ultraviolet-A): long- wave solar
rays of 320-400 nanometers (billionths
of a meter). Although less likely than
UVB to cause sunburn, UVA
penetrates the skin more deeply, and
is considered the chief culprit behind
wrinkling, leathering, and other
aspects of "photoaging." The latest
studies show that UVA not only
increases UVB 's cancer-causing
effects, but may directly cause some
skin cancers, including melanomas.
UVB (ultraviolet-B): short-wave solar
rays of 290-320 nanometers. More
potent than UVA in producing
sunburn, these rays are considered
the main cause of basal and
squamous cell carcinomas as well as
a significant cause of melanoma.
Ultraviolet
Light
Suncreens



Sunblocks and sunscreens: Sunscreens chemically absorb UV rays,
sunblocks physically deflect them. Sunscreen has long blocked UVB
effectively, but until recently provided less UVA protection. New
ingredients such as octylcrylene and the benzophenones have improved
sunscreen's defenses against shorter UVA rays, and the revolutionary
chemical avobenzone (Parsol 1789) works against all UVA wavelengths.
Sunblocks have also markedly improved. New preparations such as
micronized titanium dioxide are less conspicuous on the skin and offer
substantial protection against both UVA and UVB.
SPF (sun protection factor): measures the length of time a product
protects against skin reddening from UVB, compared to how long the skin
takes to redden without protection. If it takes 20 minutes without
protection to begin reddening, using an SPF 15 sunscreen theoretically
prevents reddening 15 times longer -- about 5 hours. (Actually, it may
take up to 24 hours after sun exposure for redness to become visible.) To
maintain the SPF, reapply sunscreen every two hours and right after
swimming.
Look for new DNA protecting
Sunscreen

Contains enzymes in
liposomes that initiate
repair of DNA,
particularly at the
pyrimidines that have
fused together.