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Integumentary SystemBiology II
“The finest clothing made is a person's own skin, but, of course, society demands something more than this.”
Mark Twain
Case Study
•The brown recluse spider has a venom that contains an enzyme called phospholipase.▫This destroys the phospholipid bilayer that
makes cell membranes.•The venom liquefies the cells of its prey,
allowing it to feed by sucking in the nutrients.
Case Study
•Brown recluse spiders have small chelicerae (fangs),so the bite doesn’t go deep and the damage is superficial.
•Enzymes can be re-used over and over again, so the tissue damage gradually gets deeper, eventually reaching the blood vessels and muscle underneath.
Case Study
•The outermost layers of skin exist to prevent foreign substances from entering the body.
•The resulting tissue damage from the bite is highly prone to infection, as these outer layers are broken down.▫Infection is the biggest
long-term risk from this injury.
• The longer the bite is left untreated, the more tissue damage that occurs, and the greater the risk of infection.
The Integumentary System• The integument is the largest system
of the body.
▫ 16% of body weight
▫ 1.5 to 2 m2 in area
• The integument is made up of two
parts Cutaneous membrane (skin)
Accessory structures (sweat glands,
etc)
Subcutaneous fat and connective
tissue.
•The cutaneous membrane has two components
▫Outer epidermis
Made of epithelial tissues.
▫Inner dermis
Made of connective tissues.
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•Accessory Structures
▫Originate in the dermis▫Extend through the epidermis
and eventually reach the skin surface
Hair
Nails
Exocrine glands (sweat and
oil)
The Integumentary System•Subcutaneous layer (a.k.a.
hypodermis)
▫Made of loose areolar connective tissue
▫Located directly below the dermis
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The Integumentary System•Connections to Other Body Systems
▫Cardiovascular system
Blood vessels are present in the dermis layer.
▫Nervous system Sensory receptors for pain, touch, and
temperature are also present in the dermis layer.
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Injection Points
•There are three main injection points based on integumentary anatomy:▫Intradermal occurs inside the dermis
layer.▫Subcutaneous occurs below the dermis
layer in subcutaneous connective tissue.▫Intramuscular goes through the entire
integument into the muscles underneath.
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Injection Points
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Introduction to the Integumentary System•Functions of Skin
▫Protects underlying tissues and organs
▫Excretes salts, water, and organic wastes
(glands)▫Maintains body temperature (insulation and
evaporation)
▫Synthesizes vitamin D3
▫Stores lipids
▫Detects touch, pressure, pain, and temperature
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Epidermis• The epidermis is made of
avascular stratified squamous epithelium.
▫Avascular means no blood
vessels.▫Stratified squamous means
multiple layers of flattened cells.▫As there are no blood vessels,
nutrients and oxygen must reach these cells by diffusion from capillaries in lower layers.
Epidermis•Keratinocytes are cells in the epidermis
that contain large amounts of keratin, a hard protein.
These are the most abundant cells in the
epidermis
Forms a layer of dead, protective cells.
Found on all exposed skin surfaces except
eyes
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Epidermis• Skin has different thicknesses,
depending on where it is in the body.
▫ Thin Skin
Covers most of the body
Has four layers of keratinocytes
▫ Thick Skin
Covers the palms of the hands and soles
of the feet
Has five layers of keratinocytes
Hyperkeratinosis: Excess keratin production
Life Cycle in the Epidermis• Cells of the epidermis pass
through five different stages as they grow and move outward.
• Cells begin at the base (near the dermis) and gradually move towards the outer surface.
• Each layer is called a stratum.
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Stratum Germinativum•The “generative” layer.
▫ Name comes from the presence of many
germinative (stem) cells.
▫ Strongly attached to the dermis by desmosomes.
▫ Forms a strong bond between epidermis and
dermis
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Stratum Germinativum•The Stratum Germinativum has a few
specialized types of cells:▫Oval-shaped receptor cells are found in hairless
areas of skin that specifically respond to touch.
▫Melanocytes containing the pigment
melanin. Melanin, along with carotene (orange pigment) creates
different tones of skin color.
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Skin Color•Skin color is a
polygenetic trait, meaning it is controlled by more than one gene.
•Certain genes increase the size and number of melanocytes.
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Tanning•Ultraviolet light in small doses helps the
body produce Vitamin D.•Large doses cause DNA damage,
accelerates skin aging, and increases the risk of cancer.▫The skin responds by producing more melanin,
which produces the darkened effect.▫Individuals with fair skin may not have enough
melanocytes to achieve this protection.•Tanning beds specifically produce
ultraviolet light to induce the production of melanin.
•Stratum Spinosum
▫The “spiny layer”▫Cells continue to
divide and produce keratin.
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•Stratum Granulosum
▫The “grainy layer” ▫Cells lose their nuclei,
stop dividing and begin producing much more keratin.
▫Keratin is a tough protein that is also found in the outer skin, fingernails, and hair.
•Stratum Lucidum
▫The “clear layer”▫Found only in thick
skin, not in thin skin.▫These cells are so far
away from the blood supply that sufficient nutrients cannot diffuse to them, causing them to die.
•Stratum Corneum▫The “horn layer”▫This is the exposed
surface of skin 15 to 30 layers of
keratinized cells, makes up about 75% of the epidermis.
Water resistant. Shed and replaced
every 2 weeks.
Dust•Indoor dust has three main components:
▫Dead skin cells▫Dried feces and corpses of dust mites
Microscopic arachnids that eat shed skin cells.
Most likely cause of a dust allergy.▫Tiny fibers from clothing.
The Dermis•Located between epidermis and
subcutaneous layer.
•Anchors epidermal accessory structures
(hair follicles, sweat glands)
•Has two components
▫Outer papillary layer
▫Deep reticular layer
•Papillary Layer▫Consists of loose areolar tissue▫Contains smaller capillaries, tiny lymph glands,
and sensory neurons
▫This layer forms epidermal ridges
(fingerprints) Purpose is not fully known.
Hypotheses: Leftover from primate ancestors that gripped and climbed
rough surfaces.
Drains water quickly to maintain grip when wet.
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•The Reticular Layer▫Consists of dense fibrous connective tissue▫Contains larger blood vessels, lymph vessels,
and nerve fibers▫Contains collagen and elastic fibers
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The Dermis•The dermis contains two types
of proteins: Collagen fibers:
very strong, resist stretching but bend easily
provide flexibility Elastic fibers:
permit stretching and then recoil to original length
limit the flexibility of collagen fibers to prevent damage to tissue
Skin is flexible yet resistant.
The Dermis▫Collagen and elastic fibers in the dermis
are arranged in parallel bundles that travel in a specific direction.
▫The direction of these fibers influence how well a cut (or incision) will heal. A parallel cut will remain shut, heals well
A cut across (right angle) pulls open and
scars
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The Dermis
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The Dermis•The dermis contains all the arteries and
veins that supply skin cells with nutrients and oxygen.
•Damage to blood vessels results in “black–and–blue” bruising as the hemoglobin and other cell components gradually break down and reabsorb.
•All nerves are also in this layer.
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Tattoos•Ink is injected into the
upper dermis layer of the skin using a hollow needle.
•The dermis is used because the cells are more stable and do not continually move up, like the epidermis.
Tattoos and MRI• Minimyth: Tattoo ink contains small amounts of metal
ions. How will it be affected by an MRI (magnetic resonance image) scan?
• http://www.youtube.com/watch?v=AiE3in71YEo&noredirect=1
Figure 5–9 Dermal Circulation.
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The Hypodermis
•The subcutaneous layer lies directly below the dermis.▫This layer is made of areolar and adipose
tissues.▫The primary function of this layer is fat storage
and an anchoring point for the rest of the skin. What is the fattiest part of chicken?
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Accessory Structures•Hair, hair follicles, sebaceous glands,
sweat glands, and nails are all considered accessory structures.
▫Each is located in the dermis.
▫All project through the skin surface
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Hair•The human body is covered with hair,
except▫Palms
▫Soles
▫Lips
•Functions of Hair▫Protects and insulates
▫Guards openings against particles and insects
(e.g. nasal passages)
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Hair•The Hair Follicle
▫Is located deep in dermis▫Produces hair, which is made
of nonliving keratin protein.▫Base is surrounded by
sensory nerves. This makes hairs especially
sensitive to detecting touch or motion.
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Hair•Accessory Structures of Hair
▫Arrector pili
Involuntary smooth muscle
Causes hairs to stand up
Produces “goose bumps”
Considered a vestigial structure in humans.
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Hair•Which types of
tissue are present in this slide?
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Hair•Hair Color
▫Hair color is the result of two different types of melanin pigment produced by melanocytes at the hair root.
▫One type of melanin causes red color, the other dark brown/black.
▫Determined by genes.
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Sebaceous Glands and Sweat Glands•Exocrine Glands in Skin
▫Sebaceous glands (oil glands)
Produce oil, which helps to protect hair and
skin.
Help to control bacteria.
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Sebaceous Glands and Sweat Glands
What types of tissue are present around sebaceous glands?
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Sebaceous Glands and Sweat Glands•Apocrine sweat glands
▫Found in armpits and groin.
▫Produce a sticky, cloudy secretion.
▫Breaks down and releases odors.
▫May contain pheromones.
▫Purpose in humans not fully known.
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Sebaceous Glands and Sweat Glands
What kinds of tissue are found lining apocrine sweat glands?
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Sebaceous Glands and Sweat Glands•Eccrine sweat glands
▫Widely distributed on body surface, especially on the palms of hands and soles of the feet.
▫Discharge water and salts directly onto skin surface
▫Functions of eccrine sweat glands: Cools skin Excretes water and electrolytes (salt ions) Flushes microorganisms and harmful chemicals from
skin
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Sports Drinks and Sweat
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Sebaceous Glands and Sweat Glands•Other Integumentary Glands
▫Mammary glands
Produce milk
▫Ceruminous glands
Produce cerumen (earwax)
Protect the eardrum
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Nails•Nails protect fingers and toes
▫Made of dead cells packed with keratin
•Nail production▫Occurs in a deep epidermal fold near the
bone called the nail root
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Skin Anatomy
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Epidermis
Dermis
Hypodermis (Subcutaneous))
Stratum Corneum
Hair
Adipose Tissue
NerveHair FollicleNerve
Arector Pili Muscle
Sebaceous Gland
Sweat Gland
Stratum Germinativum
Sweat Pore
Repair of the Integument
1. Bleeding occurs
2. Inflammation is triggered, increasing blood flow.
Repair of the Integument
3. A scab stabilizes and protects the wound.
4. Cells from the stratum germinativum surround the injured area.
5. White blood cells clean the area of bacteria and foreign substances.
Repair of the Integument
6. Special cells
called
fibroblasts
move in,
producing scar
tissue that fills
in the area
underneath the
epidermis.
Skin Damage•Sagging and wrinkles (reduced skin
elasticity) are caused by▫ Dehydration▫ Age▫ Hormonal changes▫ UV exposure
•Stretch Marks▫ Thickened tissue resulting from
excessive stretching of skin due to: pregnancy weight gain
Effects of Aging
•Effects of aging include
▫Thinning of the epidermis.
▫Decreased melanin production.
▫Decreased glandular activity (sweat and oil
glands)
▫Reduced blood supply, slower healing rate.
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Epidermis•Hydration
▫Results from immersion in hypotonic
solution (e.g., freshwater [osmosis])
▫Causes swelling of epithelial cells, evident
on the palms and soles
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Skin Disorders
•Cyanosis▫Bluish skin tint
▫Caused by severe reduction in blood flow or blood-oxygen levels.
•Jaundice▫Buildup of bile from the
liver.
Vitamin D3 Deficiency
•Vitamin D3
▫Epidermal cells produce vitamin D3 in the
presence of UV radiation.▫Liver and kidneys convert
vitamin D3 into a
compound that helps absorption of calcium and phosphorus.
▫Insufficient vitamin D3
can cause rickets.
Botox
•Botulinum toxin is one of the most powerful neurotoxins known.
•Produced by the bacteria Clostridium botulinium.
•Botox blocks a neurotransmitter that signals the contraction of muscles. ▫This can diminish certain types of wrinkles
(brow lines, frown lines)•Side effects – can immobilize too much of
the face, affecting facial expressions.
Botox
•Effects will wear off; Injections must be repeated every 4-6 months.
Skin Infections
•Fungal Infections▫Athlete's foot▫Toenail fungus▫Ringworm
•Each is caused by related fungus species. •Spread by contact, especially prevalent in
dark, moist areas.▫Locker room, shower floors▫Shared footwear
•Only antifungal medications are effective (e.g. Lamisil)
Skin Infections•Bacterial infections
▫Impetigo▫Boils▫Staph infections
•Caused by a species of bacteria (Staphylococcus aureus) that colonizes in skin and begins producing toxins.
•Treated with antibiotics.•Transmitted by contact.•MRSA is a strain of Staph that is resistant
to many antibiotics.
Viral Infections• Chicken pox
▫ Infects epidermal cells, causing itching and raised bumps.
▫ Airborne and direct contact.• Warts
▫ Causes the outer strata of the epidermis to overgrow.
▫ Spread by direct contact.• Cold sores
▫ Caused by the herpes virus. Able to lay dormant within infected cells for an entire lifetime.
Viral Infections•Viral infections are difficult to treat. The
best course is usually prevention with an immunization shot.
Irritation•Dermatitis
▫An inflammation of the papillary layer of the dermis.
▫Caused by infection, radiation, mechanical irritation, or chemicals (e.g., poison ivy)
▫Characterized by itch or pain•Itching
▫Nerves begin firing when an irritant lands on the skin surface and is rubbed into the dermis.
▫Scratching is meant to remove the irritant with the nails.
Acne•Acne is the
formation of pimples due to the blockage of sebaceous gland pores.▫Whiteheads are
infected and black heads are not.
▫The white pus is made up of white blood cells.
Skin Burns• First-degree burns
▫ Only epidermis is damaged▫ Skin is red and swollen▫ Sun burns
• Second-degree burns▫ Epidermis and upper dermis are damaged▫ Skin is red with blisters▫ Boiling water burns
• Third-degree burns▫ Destroys all layers, including nerves and blood vessels.▫ Burn is gray-white or black, often no pain felt.
Skin Cancer•There are different types of skin cancer,
classified based on the type of cell that grows uncontrollably:▫Basal cell carcinoma affects cells in the
bottom stratum of the epidermis. The least malignant and most common type of
skin cancer.
Skin Cancer
•Squamous cell carcinoma occurs in the second stratum (the “spiny” layer) of the epidermis.
•These tumors must be removed quickly, as they can metastasize through nearby lymph nodes and into the rest of the body.
•This form of cancer is usually caused by overexposure to the sun.
Skin Cancer
•Malignant melanoma is the most dangerous type of skin cancer.
•Caused by out of control growth in melanocytes.
•Can metastasize quickly to blood and lymph vessels.
•Can be differentiated from regular moles by the ABCD rule.
Skin Cancer•A = Asymmetry
▫Two sides of pigmented mole do not match•B = Border irregularity
▫Borders of mole are not smooth•C = Color
▫Different colors in pigmented area•D = Diameter
▫Spot is larger then 6 mm in diameter