Chapter 4
Guiding Question:
What are the components of the
integumentary system?
 Not just a covering for the body
• Largest organ
 Blood vessels, connective tissue structures, glands,
hair, nails, nerves, skin
• Plays a large role in homeostasis
 Has inherent and adaptive
• Calluses
• Darken in sun
• Elasticity
• Sensitive to moisture
Guiding Questions:
1.) What embryonic layers form the
integumentary system?
2.) Describe the development of the
integumentary system.
3.) What are some various causes of hair
 Ectoderm
& mesoderm in origin
 Skin is a complex structure
 Many things can go wrong in its
 Let’s make a timeline!
 Simple
ectoderm epithelium over
• outermost layer of skin form a simple
squamous tissue that becomes stratified as
the embryo develops from the ectoderm
 Deeper
parts of skin begin to form from
mesoderm (dermis, hypodermis)
 8-9
wks: mesenchyme begins to mature
and fibroblasts form, and dents occur
in the upper squamous layer
 form lanugo.
• 10 weeks: ridges form between the outer
and inner layers of skin—so don’t separate
when rubbed
• 11 weeks: small nails at the tips of fingers &
toes, followed by development of special
blood vessels in the layers of skin
 Angiogenic factors stimulate the production of
these vessels
• 20 weeks: Glandular structures form
 Inward growths of the outermost squamous
cell layer
 Will eventually produce oils and sweat
• 25 weeks: Pigmentation
• About 26 weeks: melanoblasts mature
into melanocytes (build pigments)
• nervous tissue structures develop
 What
are the three major layers of the
 Describe the basic characteristics of the
three major layers of the skin
(recommend a chart)
1. Epidermis: Epithelial
 Superficial & thinnest
 cells are very tightly packed
 New cells produced here
2. Dermis: Connective
 Deep to epidermis & thick
 Primarily connective tissue
 loosely packed cells
3. Subcutaneous/Hypodermis (adipose tissue)
• Deep to the skin/dermis
• Layer of insulation
 Outermost: Stratum
• Dry, dead,
• keratin filled (waterproof,
 Stratum Granulosum
• Waterproof
• Contains granules of keratin
 Stratum Spinosum
• “Prickly” layer
• Contains Langerhans cells
(fight infections)
 Stratum
/ basale
• Cells undergoing mitosis,
move up and horizontally
• Contains malpighian
layer or “Pigment layer”
with melanosomes
• Forms epidermal ridges
Stratum corneum:
Dead squamous cells
Stratum lucidum: (only in
thick skin); oils from
lysosome disintegration
Stratum granulosum:
Granules with lipids and
keratin – forms waterproof
Stratum Spinosum:
cuboidal cells, desmosomes
hold together >> spiny
Stratum Germinativum/
Basale: dividing columnar
 Specialized
cells within epidermis:
• Melanocytes
 Melanin: pigment, inc. w/sun (protection)
• Keratinocytes
 Keratin: tough, waterproof material
 Abrasion resistance for cells
• Langerhans cells
 Immune response against microbes invading the skin
Second layer of the skin
 Collagen, elastin
fibers– scattered
 Dense, irregular
connective tissue
 Loose, connective tissue = areolar
connective tissue
• Binds blood vessels, membranes, muscles,
nerves, and skin to other structures
• Contains extensive meshwork of protein fibers
 Involved primarily in body growth
 Connective tissue maintenance
 Wound healing
Dermal papillae: parallel rows of
peg-like projections
• Unique to each individual; akin to
Third layer of the skin
 Third, innermost
layer of the skin
 Thickness, composition vary throughout
 Composed of loosely-arranged elastic
fibers that anchor the skin to the fascia
• Sheet of fibrous connective tissue
• Covers muscles, skull bones, some organs
 Large
amount of adipose (fat) cells
 Large network of blood vessels,
capillaries, lymphatic vessels
3 Types:
• Ceruminous
• Sebaceous
• Sweat/sudoriferous
cerumen (waxy secretion),
an apocrine secretion (ear wax)
Found lining ear canal
 Holocrine
glands (secrete whole dead
 Produce, store abundance of fat, which
burst and die, releasing sebum
 Sebaceous
• Secrete oil (sebum) for hair/skin
• Ducts open into hair follicles
• Accumulated sebum enlarges ducts>>white
• Darkened sebum>>black head
 Sudoriferous/Sweat
• Eccrine Glands
 Widespread
 Watery Fluid
 Separate pore
• Apocrine Glands
 Armpits/Genitals
 Thick/milky fluid
 Secrete into hair follicle
 Aprocrine
• Odorous, sweat-like material in armpits, navel, groin
region, areolae
• Inactive until puberty
• Contain pheromones
• Broken down by bacteria, creating odor
 Eccrine
• Skin of armpits, foreheads, palms, soles
• Mostly secrete water, w/ salts, organic compounds,
and wastes (like urea)
• Microbes feed on these as well, producing odors
 Specialized
• Hair follicle: cells of the epidermis extend into
the dermis forming a small tube
Hair bulb: base of the follicle
Hair papilla: cluster of cells (live); nourished by
Root: part of hair hidden in follicle
Shaft: visible part of hair
 Sensory
• Communicate information from environment to
the body
• Found in all skin layers
 Mostly in innermost regions, fascia
 Free
nerve endings/Nociceptor
• Pain-sensing structures
• Found throughout inner part of epidermis
• Detect chemicals associated with tissue damage
and bleeding
 Merkel
• Sensitive to gentle physical sensation
• Found in stratum germinativum
• Abundant in fingertips
 Elongated, club-shaped
pile of
connective tissue
 Upper region of dermis (in dermal
 Respond to touch
 Look
like onions
 Deeper parts of hypodermis
 Hard pressure, vibrations
 Pressure, constant
 Sensitive
touch receptors
 Found mostly in mucous membrane of
 Merely
a keratin secretion
 Nail root
• Lies beneath skin-nail fold
• Grow back as long as nail root and skin-nail fold
are not severely damaged
• Grow 1/8 in per month
 Modified
stratum corneum
 Grows from an individual follicle buried
in subcutaneous layer
 Specialized
Structures (continued)
• Arrector pili: tiny, smooth muscle attached to
base of dermal papillae & side of hair follicle
 Contracts: pulls on both simultaneously>>goose
 What
are the major roles of the
integumentary system?
 What are “commensals”?
 How does heat regulation in the skin
 How does sensation in the skin work?
 Briefly describe the three classifications
of burns
 Protection
 Heat
 Sensation
 Waste excretion
 The
skin protects from:
• Chemical Damage
 Can break down connections between cells
 Can disintegrate cells
 Sweat dilutes & neutralizes
 Cerumen and sebum are oily barriers
 Repels water
 Repels dangerous chemicals that are dissolved in water
 Prevents water from escaping the body through the skin.
 The
skin protects from:
• Mechanical Damage
 Any type of force that can compress, erode, stretch or
tear the skin.
 Loose connective tissue = flexibility
 Shedding stratum corneum = reduce erosion
 Calluses, adipose tissue and reticular fibers = shock
absorption to minimize compression damage
 The
skin protects from
• Microorganism damage
 Produce destructive secretions in sebum / sweat
 Kept in check by chemicals that benefit commensals—
”good” bacteria and yeast that reduce the chance that
harmful bacteria will survive on the skin.
 Shedding of stratum corneum removes microorganisms
 The
body’s ability to maintain a constant
internal temperature (98.6F)
• Blood vessels contract / expand
• Evaporation of the sweat from the surface
• Adipose tissue is a natural “blanket”
 Sensation: received
stimuli from the
environment which is interpreted in a
way that the brain can comprehend
• Done by sensory nerves in the skin
• Cold, heat, injury, pressure, stretching, touch
• Transducers: nerve cells that convert various
environmental messages into body signals.
 Eccrine
sweat glands
• Removes urea, organic chemicals, and excess
• Not as efficient as the Excretory System
 Other
• Vitamin D production when exposed to sunlight
• Predictor of a person’s health
 Skin
loses ability to maintain homeostasis
locally and for the whole body
 Sun, cooking, acids, bases, corrosive
chemicals, electricity, fires, and steam
 Damage the skin differently
 Severity of burn is based on the extent of
the skin damage.
 Reddening,
 Superficial
 Steam, sun
 Damage
to Strata
spinosum & basale
 Blisters, reddening,
swelling and fluid
build up under the
Entire epidermis affected, could be missing so
stratum basale not available
 Damage to dermis: nerve cell loss
 Pain registers b/c histamine from immune
system is released in response to the damage.
 Susceptible to dehydration, loss of body heat,
and infection
 Skin
entirely damaged; bone, muscle
underlying skin damaged as well.
 (Too
graphic to show)
 Guiding
• What are the three major categories of disease
in the integumentary system?
• What are the various types of degenerative skin
disorders? Genetic skin disorders? Infectious
skin disorders?
 Degenerative
• Progressive deterioration of tissue,
environmental or physical stress
 Genetic
• Mutations
 Infectious
• Microorganisms that damage tissues and organs
 Solar
• People in their 30s w/ overexposure
 Dermatitis
• Cosmetics
• Facial cleansers
• Toners
• Can accelerate skin aging
 Skin
• Underlying genetic component—precancerous
• If damaged, genes cause abnormal divisions of
• Sun exposure
 Irregularly shaped black or brown spots that can
develop into open sores
• Injury deep in the skin
 Discolored blisters or sores
Moles: flat squamous cell tumors
Skin tags: soft knobby tumors that grow out of
 Seborrheic keratosis: Black to brown growth on
face or body that creates a greasy, rough
appearance to the skin
 Sebaceous hyperplasia: caused by oil glands,
small yellow bumps with an opening in the
 Syringomas: sweat-gland duct tumor, small
lumps on the cheeks and eyelids
 Lipomas: fat cell tumor, don’t cause problems
 Acne: stimulated
by hormonal changes
that cause and increase in sebum around
the hair follicles.
• Furuncle or boil: a buildup of dead cells and
blood components caused by the inflammation
of hair follicles.
• Cysts or nodules: a sack-like structure filled with
a fluid or semi-solid
• Bacteria that feed on the acne pimple produce
chemicals that aggravate acne
 Psoriasis
• Increased amt of skin cell production
• Causes a build up of thick scales on skin.
• Unsightly, inflamed, painful, swollen
 Birthmarks
• Port wine: begins at birth and grows, can bleed
• Spider veins: central blood vessel with smaller
vessels branching from it
• Strawberry hemangiomas: enlarged blood
 Vitiligo
• Michael Jackson
• White spots—hypopigmentation
• Reduced melanocytes
 Albinism
• No melanin production in the eyes, hair or skin
 Melasma
• Brown patches on both sides of the face
• Symmetrical
• Does not completely disappear
 Staphylococcus
aureus (bacteria)
• destructive secretions that erodes and inflame
the skin
• Impetigo, SSSS, folliculitis
 Candida
albicans (fungus)
• Yeast in digestive system and female
reproductive tract infect skin when immune
system is compromised
• Degrade tissue and cause inflammation
 More
fungal infections = dermatophytes
• Eat keratin-rich materials: hair, nails, and outer
layers of epidermis
• Itching, hair loss, deformation of nails
• Ringworm (aka tinea)
 Contracted from furry pets
 Spread from one person to another through contact
via clothes and skin
 Related to athlete’s foot or jock itch
 Warts
• 60 types
• HPV (human papilloma virus)
 Incurable
 Removal procedure
 Protists
• Exotic tropical diseases that are spread by insect
• Can cause severe bodily damage if spread to
internal organs
 Arthropods
• Insects with exoskeletons, segmented bodies,
jointed limbs
• Follicle mite—undetected until inflammation of
eyelash follicle occurs
• Lice—blood sucking insects that irritate skin and
spread infection as they feed
 Guiding
• What are “intrinsic” factors? How can they affect
the skin’s aging?
• What kinds of extrinsic factors can affect skin
• How does lifestyle accelerate skin aging?
 Extrinsic
• Also external aging
• Environmental factors: disease, pollution, sun
 Intrinsic
• Natural maturation
• Also internal aging
• Accelerated by stress—pathology of other organ
systems or environmental interactions
 Characteristics
of skin aging
• Loss of head hair
• Graying and whitening of hair
• Excessive growth of body and facial hair
• Wrinkling
• Drying of the skin due to diminished oil
• Skin sagging due to muscle atrophy
• Regular irritation due to microbial population
changes on the skin
 Impossible to stop
• Natural decline of cells
• Can be slowed by living in a mild environment
• Elastin is naturally degraded by the dermis and
subcutaneous layers
 Makes the skin less flexible, thinner, more brittle
 Decrease in blood flow slows cell division in basale &
causes thinning of the epidermis
 More difficult to repair skin damage
 People with vascular diseases exhibit premature
 Decrease
in melanocytes, nerves
• More susceptible to environmental damage
• Older skin can’t protect from UV and has
difficulty registering injury.
 Susceptible
to DNA damage
• Oxidizing chemicals and sunlight
• Cause cancers and tumors
 How to slow…
• Diet, reducing exposure to UV, avoiding skin
irritation, not smoking, protecting from air
 Smoking reduces blood flow to skin
 Can’t heal
 Decreases ability to maintain body’s temp
 Skin needling
 Promotes growth and swelling in wrinkled depression areas
 Makes skin smooth for a while
• Take care of skin at a young age…difficult to
reverse skin aging once the damage is done

Integumentary System