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