Download CHAPTER 5: The Integumentary System

Chapter 5:
The Integumentary System
The structures
and functions of the
integumentary system.
Structure of the Integument
• 16% of body mass
• Composed of:
1. Cutaneous Membrane:
1. Epidermis– Superficial epithelium
2. Dermis – underlying CT with blood supply
2. Accessory Structures: originate in dermis
1. Hair
2. Nails
3. Exocrine Glands
Parts of the
Integumentary System
Figure 5–1
Functions of the Integument
•
•
•
•
•
•
Protects underlying tissues from infection,
exposure and dehydration
Excretes salts, water, and organic waste
Maintains normal body temp:
- conserve and radiate heat
Synthesizes Vitamin D3 for calcium metabolism
Stores Nutrients and Fat
Sensory detection:
- touch, pressure, pain, and temp.
Connections
• Circulatory system:
– blood vessels in the dermis
• Nervous system:
– sensory receptors for pain, touch, and
temperature
The main
structures and functions
of the epidermis.
Epidermis
• Avascular stratified squamous epithelium
• Nutrients and oxygen diffuse from
capillaries in the dermis
Cells of the Epidermis
• Keratinocytes:
– contain large amounts of keratin
– the most abundant cells in the epidermis
• Thin Skin: Hairy
– Covers most of the body
– Has 4 layers of keratinocytes
• Thick Skin: No Hair
– Covers the palms of the hands and soles of the
feet
– Has 5 layers of keratinocytes
Structures of the Epidermis
• The 5 strata of keratinocytes in thick skin
Figure 5–3
Layers of the Epidermis
• From basal lamina to free
surface:
–
–
–
–
–
stratum germinativum
stratum spinosum
stratum granulosum
stratum lucidum
stratum corneum
• Transit from stratum basale to
stratum corneum:
– 15-30 days
• Duration at stratum corneum:
– 7-14 days
• Complete turnover ever 25-45
days
1. Stratum Germinativum/Basale
• The “germinative layer”: Single Layer
–
–
–
–
has many germinative (stem) cells or basal cells
is attached to basal lamina by hemidesmosomes
forms a strong bond between epidermis and dermis
Cells:
• basal/germinative cells (stem cells), melanocytes (melanin),
some Merkel cells in hairless skin (touch receptors)
Structure:
• Epidermal ridges (e.g., fingerprints)
• Dermal papillae (tiny mounds):
– increase the area of basal lamina
– strengthen attachment between epidermis and dermis
Layers of the Epidermis
2. Stratum Spinosum:
– 8-10 layers keratinocytes attached by desmosomes
– some cells can divide
– some Langerhans cells present (immune response)
3. Stratum Granulosum:
– 3-5 layers keratinocytes producing keratin fibers,
keratohyaline granules, and lamellated granules
• Keratin = basic structural component of hair and nails
• Keratohyaline = Promotes dehydration of the cells and crosslinking of keratin fibers
– No cell division, nuclei and organelles being to
disintegrate
Layers of the Epidermis
4. Stratum Lucidum:
- thick skin only, flat packed keratin filled
keratinocytes
5. Stratum Corneum:
– 15-30 layers dead keratinocytes that have been
keratinized (cornified)
• Soft keratin fibers glued in paralled arrays by
keratohyaline
– Extracellular space filled with glycolipids from
lamellated granules
• Cornified = water and chemical resistant
– not water proof since interstitial fluid can evaporate
Ridges and Ducts
The corrugated border between dermis and
epidermis helps bond the epidermis and
dermis
- increased surface area for attachment
In thick skin epidermal ridges show on the
surface as fingerprints:
Function – enhance gripping
Figure 5–4
Dandruff is caused by excessive shedding of
cells from the outer layer of skin in the scalp.
Thus dandruff is composed of cells from which
epidermal layer?
1.
2.
3.
4.
stratum germinativum
stratum spinosum
stratum corneum
stratum granulosum
A splinter that penetrates to the third
layer of the epidermis of the palm is
lodged in which layer?
1.
2.
3.
4.
stratum lucidum
stratum germinativum
stratum spinosum
stratum granulosum
Some criminals sand the tips of their fingers so
as not to leave recognizable fingerprints. Would
this practice permanently remove fingerprints?
Why or why not?
1. Yes, because the dermal papillae die if
exposed.
2. No, because the ridge patterns
regenerate.
3. Yes, because the stratum germinativum
thickens hiding ridge patterns.
4. No, because different ridge patterns
will appear with re-growth.
Characteristics of Skin
• Skin is water resistant but not water proof:
– Insensible perspiration:
• Water from interstitial fluids evaporate
• Water loss can not be seen or felt
• water loss through skin: ~500ml (1 pint)/day
– More if damaged (e.g. burn)
– Sensible perspiration:
• Aware of water loss
• Produced by active sweat glands
Characteristics of Skin
– Callus:
• Thickening of skin, due to friction
– Blister:
• Separation of epidermal layers or epidermis
form dermis
• space fills with interstitial fluid
Skin Color
• Pigment based: epidermal pigments
and blood pigments contribute to the
color
1. Epidermal Pigmentation
2. Dermal Circulation
Skin Color
1. Epidermal Pigmentation
A. Carotene: yellow-orange, from diet
- converted into Vitamin A
- localized to epithelium
- functions in normal maintenance
of epithelia and photoreceptors
- excess accumulates in stratum
corneum
B. Melanin: Brown, from melanocytes
- for UV protection
1. Epidermal Pigmentation
• Melanocytes: in stratum basale
– Synthesize melanin from tyrosine
(amino acid)
– Packaged in melanosomes
– Melanosomes are transferred to
cytoplasm of keratinocytes
– Cluster around top side of nucleus
– Eventually digested by lysosomes
• Everyone has ~1000
melanocytes/mm2
– Pale People: small melansomes,
present on in stratum basale and
spinosum
– Dark People: larger, greater number
of melansomes, retained up through
stratum granulosum
1. Epidermal Pigmentation
• Freckles:
– Overproduction of melanin form single melanocytes
• UV exposure:
– Some needed for Vitamin D3 production
– Excess = damage (DNA mutation)
• Harm Fibroblasts  impaired maintenance of the dermis
resulting in altered CT structures
– Wrinkles
• Chromosomal damage of Epidermal cells or melanocytes
 cancer
– Squamous cell carcinoma
– Melanoma
Skin
2. Dermal Circulation: hemoglobin pigment
- Oxygenated blood:
- red color, hemoglobin in RBCs, through skin=pink
- Vasodilation  skin looks more red
- Vasoconstriction  skin looks more pale
- Cyanosis:
- low oxygen, blood deep purple, skin appears
blue/purple
- results form low temp., heart failure, asthma
Abnormal Skin Color
• Jaundice:
– Liver fails to excrete bile
– Bile accumulates in skin = yellow
• Addison’s Disease:
– Pituitary secretes excess adrenocorticotropic
hormone, stimulates melanoctyes, excess melanin,
bronzing
• Albinism:
– Genetic mutation in melanin biosynthesis pathway
– Lack pigmentation in skin, hair and eyes
• Vitiligo:
– Autoimmune disease  destruction of melanocytes
Vitamin D3 Production
• Cells of stratum spinosum and basale:
– UV energy + cholesterol = Vitamin D3
• Vitamin D3:
– used by kidney to synthesize the hormone
calcitriol
• Calcitriol:
– necessary to signal small intestine to absorb
calcium
• No VitD  no calcitriol  no calcium
absorption  weak bones
KEY CONCEPT
• The epidermis:
– is a multilayered, flexible, self-repairing
barrier
– prevents fluid loss
– protects from UV radiation
– produces vitamin D3
– resists abrasion, chemicals, and pathogens
Why does exposure to sunlight or
sunlamps darken skin?
1. UV stimulates melanocytes.
2. Melanin darkens in sunlight.
3. Stratum corneum cells appear
brown.
4. Keratin appears brown when
heated.
Why does the skin of a fair-skinned
person appear red during exercise in
hot weather?
1. Sunlight stimulates erythrocyte
production in skin.
2. Blood is diverted to the superficial
dermis to eliminate heat.
3. Sunlight bleaches fair skin, allowing
blood to be seen.
4. Heat stimulates cutaneous blood vessels,
causing leaks.
In some cultures, women must be covered
completely, except for their eyes, when they go
outside. Explain why these women exhibit a high
incidence of problems with their bones.
1. UV light prevents calcium deposition in
bones.
2. Melanin production is necessary for
bone growth.
3. Cloth prevents oxygen from diffusing
into skin and bones.
4. UV light is necessary to produce the
hormone cholecalciferol (vitamin D3).
The structures and functions
of the dermis.
The Dermis
• Is located between epidermis and
subcutaneous layer
• Anchors epidermal accessory structures
– hair follicles, sweat glands
• Contains:
– All cells of CT proper, accessory organs of
integument, blood vessels, lymphatic vessels,
nerves, and sensory receptors
• Has 2 components:
– outer papillary layer
– deep reticular layer
Dermis
• Papillary layer:
– Thin (20%)
– Consists:
• Areolar CT
• Comprise dermal papillae
• Capillaries, lymphatics, and
sensory neurons
– Function: feed epidermis
• Reticular Layer:
– Thick (80%)
– Consists:
• Dense irregular CT
• Elastic and Collagen fibers
– Function: provide strength and flexibility
Dermis
• Collagen fibers from reticular layer
– blend into papillary and subcutaneous layers to attach
integument to body
• Wrinkles = Dermis stretched beyond its elastic
capacity
– collagen fibers damaged
• Stretch marks = collagen and elastic fibers torn
– Thickened tissue resulting from pregnancy, weight gain,
muscle gain
• Collagen and Elastin fibers arranged in parallel
bundles:
– aligned to resist the expected direction of force = lines
of cleavage
• Cuts parallel to lines of cleavage will heal faster
and with less scar than those perpendicular
Lines of Cleavage
Figure 5–7
Dermis
• Dermis highly vascularized:
– must “feed” itself and epidermis above
• Contusion:
– bruise, trauma that ruptures blood vessels but
does not break skin, blood pools in dermis and
must be removed by phagocytes (slow process)
Dermatitis
• An inflammation of the papillary layer
• Caused by
– infection, radiation, mechanical irritation, or
chemicals (e.g., poison ivy)
• Characterized by
– itch or pain
• Characteristics
– Strong, due to collagen fibers
– Elastic, due to elastic fibers
– Flexible
Skin Damage
• Sagging and wrinkles (reduced skin
elasticity) are caused by:
–
–
–
–
dehydration
age
hormonal changes
UV exposure
Sensory Perception in Integument
• Skin highly innervated for sensory
perception, mostly in dermis
1. Merkel Cells
2. Free Nerve Endings
3. Meissner’s Corpuscles
4. Pacinian/Lamellated Corpuscles
Sensory Perception in Integument
1. Merkel cells: deep layers of epidermis
- superficial touch
2. Free Nerve Endings: superficial dermis
- pain and temperature
3. Meissner’s Corpuscles: superficial dermis
- light tough
4. Pacinian/Lamellated Corpuscles: deep
dermis
- pressure and vibrations
Thin Skin
Thick Skin
Where are the capillaries and sensory
neurons that supply the epidermis
located?
1.
2.
3.
4.
reticular layer of the dermis
epidermis
papillary layer of the dermis
hypodermic layer
What accounts for the ability of the
dermis to undergo repeated stretching?
1. elastic fibers and skin turgor
resilience
2. reticular fibers and fluids
3. adipocytes and elastic fibers
4. sebaceous gland secretions
The structures
and functions of the
subcutaneous layer.
The Hypodermis
• The subcutaneous layer or hypodermis:
– lies below the integument
– Not part of cutaneous membrane
– Stabilizes position of skin while permitting
independent movement of skin and
muscles
Subcutaneous Layer
(aka Hypodermis)
• Areolar and adipose CT
• Tightly interwoven with reticular layer of
dermis
• Children: even layer of adipose
• Puberty: Adipose shifts
– Male: neck, arms, abdomen, lower back
– Female: breast, buttocks, hips, thighs
• No vital organs: safe for “SubQ” injection,
vascular for quick absorption
KEY CONCEPT
• The dermis:
– provides mechanical strength, flexibility
and protection
– is highly vascularized
– contains many types of sensory receptors
Integumentary
Accessory Structures
1.
2.
3.
4.
•
Hair and hair follicles
Sebaceous glands
Sweat glands
Nails
Accessory Structures:
–
–
–
are derived from embryonic epidermis
are located in dermis
project through the skin surface
Hair
• Human body:
– ~2.5 million hairs, 75% on body
• Everywhere except:
– palms, soles, lips, and certain genitalia
• Hair itself is dead, but is derived from
live epidermal tissue
• Hair and Hair Follicle Structure
Hair growth, texture, and
color.
Functions of Hair
• Function:
– Protects and insulates
– Guards openings against particles and insects
– Is sensitive to very light touch
• Structure of Hair Follicle:
–
–
–
–
–
Hair Follicle
Glassy membrane
Hair bulb
Hair papilla
Hair Matrix
• Structure of Hair:
– Hair root
– Hair shaft
The Hair Follicle
• Hair is produced in organs
called hair follicles
• Tube of stratified squamous
epithelium anchored in dermis
• Surrounds, supports, and
produces hair
• Two layers:
– Internal Root Sheath:
• contacts hair
– External Root Sheath:
• contacts glassy membrane
Hair Follicle Structure
• Glassy membrane
– Thick basal lamina between epithelial
follicle and connective tissue dermis
• Hair bulb consist of epithelial cells
– Expanded base of follicle that
surrounds papilla and matrix
– Responsible for producing hair by
forming the hair matrix layer
• Hair Matrix
– Dividing epithelial/basal cells and
melanocytes above papilla that form
new hair
– Cells gradually push toward the surface
• Hair papilla
– CT at base of bulb, contains capillaries
and nerves
– Supports matrix
Hair Structure
• Hair Root:
–
–
–
Embedded in dermis
Not yet fully formed
Contains live cells
• Hair Shaft:
–
–
–
1.
Pokes through epidermis
Fully organized dead hair
Three layers
Cuticle: outermost, overlapping dead keratinized
cells form shiny surface
2. Cortex: middle layer, dead cells contain hard
keratin to provide stiffness
3. Medulla: core, dead cells contain soft keratin and
air to provide flexible
Hair Structure
•
Shape of the Shaft determines feel:
–
–
–
•
Flattened shaft = kinky hair
Oval shaft = silky and wavy hair
Round shaft = straight and often stiff hair
Two types of Hair produced:
1. Vellus Hairs = “peach fuzz”
-
Lacks medulla
Covers body, at puberty hormones can trigger switch to
terminal hairs
- Vellus hairs present at the armpits, pubic area, and
limbs switch to terminal hairs in response to
circulating sex hormones
2. Terminal Hairs = head, eyebrows and eyelashes
- Thick, coarse, pigmented
Hair Color
• red: iron added
• Range yellow to black due to melanin
from melanocytes in hair matrix
– Melanin stored in cortex and medulla
With age, melanin declines, air pockets
in medulla increase = gray or white
hair
Hair Growth
• Hair in the Scalp:
– Grows for 2-5 yrs, at a rate of 0.33 mm per day
• During hair growth:
– Cells of the hair root absorb nutrients and incorporate
them into the hair structure  History of Exposure
• Result  clipping or collecting hair for analysis is helpful
in diagnosing several disorders (ex. Heavy Metals,
nucleus = DNA)
– The root is firmly attached to the matrix of the follicle
• At the end of growth:
– The follicle becomes inactive  termed club hair
• Follicle gets smaller
• Connections between the hair matrix and the club hair
root breaks down.
• Another cycle begins:
– Follicle produces a new hair
– The old club hair is pushed to the surface and shed
Hair Growth
~0.33mm/day, not continuous: cycle of growth and rest
1. Active phase:
- new hair added to hair root by dividing cells of hair
matrix (weeks – years)
2. Regressive phase:
- cells of hair matrix stop dividing
- hair root and hair papilla separate loose hair = club hair
3. Resting phase:
- cells of hair matrix and hair follicle remain inactive (1-3
months)
New Active Phase Begins
Hair length differences = difference in time spent in active phase:
eyebrows = few months
head – many years
• Shedding of the hair occurs only after the next growth
cycle begins and a new hair shaft begins to emerge.
• On average 50 - 100 hairs are shed every day.
• The percentage of follicles in the resting phase will vary
at any time depending on the body area.
• Factors that can affect the hair growth cycle and cause
temporary or permanent hair loss (alopecia) including:
– medication, radiation, chemotherapy, exposure to
chemicals, hormonal and nutritional factors, thyroid
disease, generalized or local skin disease, stress, and
high fevers.
Hair Growth
• Alopecia:
– Shift from terminal hair to vellus hair,
thinning/balding, some degree expected with age
• Male Pattern Baldness:
– Genetic alopecia, early age onset
– Caused by a shift from terminal to vellus hair
production due to a change in the level of sex
hormones circulating in the blood
– Treatment:
• Aimed at converting vellus hairs to terminal hairs
• Hair Removal:
– Difficult to achieve permanent result
– Any remaining matrix cells can regenerate all hair
follicle structures
Hair Function
• Head:
– UV protection
– Cushion from trauma
– Insulation
• Nostrils, Ear canals, Eyelashes:
– Prevent entry of foreign material
• Body Hair:
– sensory detection
Hair Function: Sensory Detection
• Root hair plexus:
– Sensory nerves at base of hair
follicle that detect slight
movement of hair
• Arrector pili muscle:
– Attached to every hair follicle
– Contract to stand hair
perpendicular to skin surface
• Goose bumps
– Smooth muscle: involuntary
What happens when the arrector pili
muscle contracts?
1.
2.
3.
4.
Sebum is released.
Goose bumps are evident.
Sweat is produced.
Blood flow is increased.
Once a burn on the forearm that destroys
the epidermis, and extensive areas of the
deep dermis heals, will hair grow again in
the affected area?
1. Yes.
2. No.
3. Only in areas where the deep dermis
was destroyed.
4. Only in areas where the epidermis
and deep dermis were not destroyed.
The skin glands
and secretions.
Exocrine Glands
• Sebaceous glands (oil glands):
– holocrine glands (which destroys gland cells)
– secrete sebum
• Sudoriferous Glands/Sweat Glands
A. Merocrine/Eccrine sudoriferous glands
B. Apocrine sudoriferous/sweat gland
Sweat glands:
• merocrine glands
• watery secretions
Integumentary Glands
•
All are exocrine glands
–
1.
Secrete product onto skin surface via a duct
Sebaceous glands
-
-
Holocrine secretion
Secrete sebum into hair follicle
Sebum = lipids + cholesterol + proteins +
electrolytes
Function:
- Lubricate and protect keratin
- Prevent evaporation
- Inhibit bacterial growth
Sebaceous glands active in fetus, then off
until puberty, and then back on for the
whole adult life
Acne = Inflammation of a sebaceous gland,
* Usually due to bacterial infection
Integumentary Glands
2. Sudoriferous Glands/Sweat Glands
A. Merocrine/Eccrine sudoriferous glands
- 2 to 5 million all over body
- produce sensible perspiration:
- 99% water
- electrolytes + organic nutrients
+ antibodies + antimicrobial agents
+ organic waters
- merocrine secretion
- secretion via exocytosis of vesicles
- small coiled tubular glands
- located in superficial dermis
- open directly on surface of skin
- secrete in response to high temp. or stress
Functions of Sensible Perspiration
1. Evaporation cooling of surface of skin to
reduce body temp.
2. Excrete waste electrolytes and drugs
3. Protection:
-
Prevent adherence of microbes: antibodies
Physically wash off microbes
Antimicrobial agents of kill microbes
-
Dermiciden (antibiotic)
Integumentary Glands
2. Sudoriferous Glands/Sweat Glands
B. Apocrine sudoriferous/sweat gland
-
merocrine secretion
armpits, nipples, groin
secrete into hair follicle
secretion is stick and cloudy:
- sensible perspiration + protein + lipids
microbes eat it  wastes = body odor
glands deep in dermis
Surrounded by myoepithelial cells: myo = muscle
- contraction of cells in response to sympathetic nervous system
stimulation causes discharge of secretion
Active only after puberty
Special Apocrine Sweat Glands:
1. Mammary Glands:
- Located in female breast & Secrete milk during lactation
2. Ceruminous Glands:
- Located in external ear canal & Secrete cerumen (earwax)
Integumentary Gland Control
• Merocrine sudoriferous glands:
– can be turned on and off in localized regions in
response to temperature or emotions
• Sebaceous and apocrine sudoriferous glands:
– Autonomic nervous system controls the activation
and deactivation of these glands therefore they
affect all the glands
– are either all on (body wide) or all off
– no local control
What are the functions of sebaceous
secretions?
1. inhibits the growth of bacteria
2. lubricates and conditions the
surrounding skin
3. lubricates and protects the
keratin of the hair shaft
4. all of the above
Deodorants are used to mask the effects
of secretions from which type of skin
gland?
1.
2.
3.
4.
ceruminous glands
apocrine sweat glands
merocrine sweat glands
mammary glands
Which type of skin glands are most
affected by the hormonal changes that
occur during puberty?
1.
2.
3.
4.
ceruminous glands
sebaceous glands
apocrine sweat glands
merocrine sweat glands
The structure of nails.
Nails
• Scale like projections on dorsal
surface of distal digits
• Function:
– protect tips from mechanical
stress, assist in gripping
• Consists of dead cells
containing hard keratin
• New nail formed at nail root
• Cuticle = stratum corneum
• Nail growth is continuous
How injured skin
responds and repair itself.
Injury and Repair
• Integument can function independent
of nervous and endocrine systems to
maintain own homeostasis
• Mesenchymal cells of dermis can
regenerate connective tissue
• Germinative cells (basal cells) of
epidermis can regenerate tissue
Repair of Localized Injuries
to the Skin: Step 1
• Bleeding occurs
• Mast cells trigger
inflammatory
response
Figure 5–13 (Step 1)
Repair of Localized Injuries
to the Skin: Step 2
• A scab stabilizes
and protects the
area
Figure 5–13 (Step 2)
The Inflammatory Response
• Germinative cells migrate around the
wound
• Macrophages clean the area
• Fibroblasts and endothelial cells move
in, producing granulation tissue
Repair of Localized Injuries
to the Skin: Step 3
• Fibroblasts
produce scar
tissue
• Inflammation
decreases, clot
disintegrates
Figure 5–13 (Step 3)
Repair of Localized Injuries
to the Skin: Step 4
• Fibroblasts
strengthen scar tissue
• A raised keloid forms
Figure 5–13 (Step 4)
Injury and Repair
• Repair may end up like original tissue or keloid
– Keloid = thick area of scar tissue covered by smooth
epidermis
• Burns:
– First degree burn: heals on own
• Damage to surface of epidermis
– Second degree burn: heals on own
• Damage to epidermis and superficial dermis
– Third degree burn: Requires skin grafts or
“living bandages”
• Damage to whole cutaneous layer (epidermis, dermis,
accessory structures), granulation tissue cannot form
thus no healing
Burns
• If burn > 20% of body can kill
–
It affects:
1. Fluid and electrolyte
balance
2. Thermoregulation
3. Protection from
pathogens
What do you call the combination of fibrin
clots, fibroblasts, and the extensive
network of capillaries in healing tissue?
1.
2.
3.
4.
granulation tissue
scar
scab
callus
Why can skin regenerate effectively,
even after considerable damage?
1. Stratum germinativum persists
deep within the body.
2. Stem cells persist in all components
of the skin.
3. Hypodermis will transform into
epidermis and dermis.
4. Surrounding skin spreads and fills in
damaged area.
The effects
of aging on the skin.
Age Related Changes
1.
2.
3.
4.
5.
6.
7.
8.
Stem cell activity declines:
- Skin thin, repair is difficult
Langerhans cells decrease:
- Reduced immune response
Vitamin D3 production declines:
- Calcium absorption declines  brittle bones
Glandular activity declines:
- skin dry, body can overheat
Bloody supply to dermis declines:
- tend to feel cold
Hair follicles die or produce thinner hair:
- terminal  vellus
Dermis thins and becomes less elastic  wrinkles
Sex characteristics fade:
- Fat deposits spread out, hair patterns change
Older individuals do not tolerate the summer
heat as well as they did when they were young,
and they are more prone to heat-related
illness. What accounts for these changes?
1. Blood supply to the dermis is
reduced.
2. Glandular activity declines.
3. Melanocyte activity declines.
4. All of the above.
The
integumentary system work
with other systems.
Importance of the
Integumentary System
• Protects and interacts with all organ
systems
• Changes in skin appearance are used to
diagnose disorders in other systems
Interactions with the
Integumentary System
Figure 5–15
SUMMARY
• Division of:
– integument into epidermis and dermis
– epidermis into thin skin and thick skin
• Layers of the epidermis:
–
–
–
–
stratum
stratum
stratum
stratum
germinosum
spinosum
lucidum
corneum
• Roles of epidermal ridges and dermal papillae
• Functions of specialized cells:
– Langerhans cells & Merkel cells
SUMMARY
• Skin pigments:
– Carotene & Melanin
• Metabolic functions of epidermis:
– vitamin D3 &epidermal growth factor
• Divisions of the dermis:
– papillary layer
– reticular layer
• Mobility of the dermis:
– stretch marks & lines of cleavage
• Blood supply of the dermis:
– cutaneous plexus
– papillary plexus
SUMMARY
• Role of the subcutaneous layer
• Structure of hair and hair follicles
• Glands of the skin:
– sebaceous
– sweat
– Ceruminous
• Structure of nails
• Processes of inflammation and regeneration
• Effects of aging on the integument