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Chapter 5: The Integumentary System


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Title: 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
  • Cutaneous Membrane
  • Epidermis Superficial epithelium
  • Dermis underlying CT with blood supply
  • Accessory Structures originate in dermis
  • Hair
  • Nails
  • Exocrine Glands

Parts of the Integumentary System
Figure 51
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.

  • Circulatory system
  • blood vessels in the dermis
  • Nervous system
  • sensory receptors for pain, touch, and temperature

The main structures and functions of the
  • 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
  • Has 5 layers of keratinocytes

Structures of the Epidermis
  • The 5 strata of keratinocytes in thick skin

Figure 53
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

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
  • No cell division, nuclei and organelles being to

Layers of the Epidermis
  • 4. Stratum Lucidum
  • - thick skin only, flat packed keratin filled
  • 5. Stratum Corneum
  • 15-30 layers dead keratinocytes that have been
    keratinized (cornified)
  • Soft keratin fibers glued in paralled arrays by
  • Extracellular space filled with glycolipids from
    lamellated granules
  • Cornified water and chemical resistant

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 54
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. stratum germinativum
  2. stratum spinosum
  3. stratum corneum
  4. stratum granulosum

A splinter that penetrates to the third layer of
the epidermis of the palm is lodged in which
1. stratum lucidum 2. stratum germinativum 3.
stratum spinosum 4. 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 loss through skin 500ml (1 pint)/day
  • More if damaged (e.g. burn)
  • 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
  • Epidermal Pigmentation
  • Dermal Circulation

Skin Color
  • 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
  • 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 spinnsum
  • 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)
  • Fibroblasts ? altered CT structures
  • Wrinkles
  • Epidermal cells, melanocytes ? cancer
  • Squamous cell carcinoma
  • Melanoma

  • 2. Dermal Circulation hemoglobin pigment
  • - Oxygenated blood
  • - red color, hemoglobin in RBCs, through
  • - Vasodilation ? skin looks more red
  • - Vasoconstriction ? skin looks more pale
  • - Cyanosis
  • - low oxygen, blood deep purple, skin
  • blue/purple
  • - results form low temp., heart failure,

Abnormal Skin Color
  • Jaundice
  • Liver fails to excrete bile
  • Bile accumulates in skin yellow
  • Addisons Disease
  • Pituitary secretes excess adrenocorticotropic
    hormone, stimulates melanoctyes, excess melanin,
  • 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
  • necessary to signal small intestine to absorb
  • No VitD ? no calcitriol ? no calcium
  • absorption ? weak bones

  • The epidermis
  • is a multilayered, flexible, self-repairing
  • prevents fluid loss
  • protects from UV radiation
  • produces vitamin D3
  • resists abrasion, chemicals, and pathogens

Why does exposure to sunlight or sunlamps darken
1. UV stimulates melanocytes. 2. Melanin
darkens in sunlight. 3. Stratum corneum cells
appear brown. 4. Keratin appears brown when
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
  • 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

  • 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

  • Collagen fibers from reticular layer
  • blend into papillary and subcutaneous layers to
    attach integument to body
  • Wrinkles Dermis stretched beyond its elastic
  • 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
  • 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 57
  • 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)

  • 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
  • Merkel Cells
  • Free Nerve Endings
  • Meissners Corpuscles
  • Pacinian/Lamellated Corpuscles

Sensory Perception in Integument
  • Merkel cells keep layers of epidermis
  • - superficial touch
  • Free Nerve Endings superficial dermis
  • - pain and temperature
  • Meissners Corpuscles superficial dermis
  • - light tough
  • Pacinian/Lamellated Corpuscles deep dermis
  • - pressure and vibrations

(No Transcript)
Where are the capillaries and sensory neurons
that supply the epidermis located?
1. reticular layer of the dermis 2.
epidermis 3. papillary layer of the dermis 4.
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
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

  • The dermis
  • provides mechanical strength, flexibility and
  • is highly vascularized
  • contains many types of sensory receptors

Integumentary Accessory Structures
  • 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

  • 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
  • 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
  • Expanded base of follicle where cell division
  • Surrounds papilla and matrix
  • Hair papilla
  • CT at base of bulb, contains capillaries and
  • Supports matrix
  • Hair Matrix
  • Dividing epithelial cells and melanocytes above
    papilla that form new hair

Hair Structure
  • Hair Root
  • Embedded in dermis
  • Not yet fully formed
  • Contains live cells
  • Hair Shaft
  • Pokes through epidermis
  • Fully organized dead hair
  • Three layers
  • Cuticle outermost, overlapping dead keratinized
    cells form shiny surface
  • Cortex middle layer, dead cells contain hard
    keratin to provide stiffness
  • 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
  • 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
  • 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
  • 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

Hair Growth
  • 0.33mm/day, not continuous cycle of growth and
  • Active phase
  • - new hair added to hair root by dividing cells
    of hair matrix (weeks years)
  • Regressive phase
  • - cells of hair matrix stop dividing
  • - hair root and hair papilla separate loose hair
    club hair
  • 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)
  • 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
  • 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
  • Goose bumps
  • Smooth muscle involuntary

What happens when the arrector pili muscle
1. Sebum is released. 2. Goose bumps are
evident. 3. Sweat is produced. 4. Blood flow is
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
  • 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
  • Secrete product onto skin surface via a duct
  • Sebaceous glands
  • Holocrine secretion
  • Secrete sebum into hair follicle
  • Sebum lipids cholesterol proteins
  • 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
  • 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
  • - 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
  • Evaporation cooling of surface of skin to reduce
    body temp.
  • Excrete waste electrolytes and drugs
  • 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
  • - contract in response to sympathetic nervous
    system stimulation
  • - 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

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
  • 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. ceruminous glands 2. apocrine sweat
glands 3. merocrine sweat glands 4. mammary
Which type of skin glands are most affected by
the hormonal changes that occur during puberty?
1. ceruminous glands 2. sebaceous glands 3.
apocrine sweat glands 4. merocrine sweat glands
The structure of nails, and how do they grow.
  • Scale like projections on dorsal surface of
    distal digits
  • Function
  • protect tips from mechanical stress, assist in
  • Consists of dead cells containing hard keratin
  • New nail formed at nail root
  • 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 513 (Step 1)
Repair of Localized Injuries to the Skin Step 2
  • A scab stabilizes and protects the area

Figure 513 (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 513 (Step 3)
Repair of Localized Injuries to the Skin Step 4
  • Fibroblasts strengthen scar tissue
  • A raised keloid forms

Figure 513 (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
  • Damage to whole cutaneous layer (epidermis,
    dermis, accessory structures), granulation tissue
    cannot form thus no healing

  • If burn gt 20 of body can kill
  • It affects
  • Fluid and electrolyte
  • balance
  • Thermoregulation
  • Protection from
  • pathogens

What do you call the combination of fibrin clots,
fibroblasts, and the extensive network of
capillaries in healing tissue?
1. granulation tissue 2. scar 3. scab 4.
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
  • 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 515
  • Division of
  • integument into epidermis and dermis
  • epidermis into thin skin and thick skin
  • Layers of the epidermis
  • stratum germinosum
  • stratum spinosum
  • stratum lucidum
  • stratum corneum
  • Roles of epidermal ridges and dermal papillae
  • Functions of specialized cells
  • Langerhans cells Merkel cells

  • 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

  • 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
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