The Integumentary System (skin)

• is the largest system

Skin

of the body –16% of body weight

–you have 21 square feet of it

–it weighs ~9 pounds

–it contains more than 11 miles of blood vessels

–you shed 50,000 cells every MINUTE!!!

Functions

• Protects

• infection • desiccation

• UV rays

–temperature regulation

–excretion

of Skin

you from

• Important for

(insulation and evaporation)

• it releases 3 gallons of sweat each day!

of salts, water, and organic wastes (glands)

• Synthesizes vitamin D3

Detects sensations

Functions of Skin

–which you need to extract calcium from your diet and incorporate it into your bones!

• –touch, pressure, pain, and temperature: as a

huge sensory receptor, the skin is your constant communication with the outside world First Line of Defense!

Skin is one huge sensory organ! It is responsible for sending information to the brain to protect the body from injury.

–Nerve sensory receptors for •pain

• touch

•vibration

• pressure

•temperature

Components • Outer Epidermis :

– epithelial tissue • stratified squamous keratinized • loose and dense

• Inner Dermis : – connective tissue

of Skin

of Epidermis Types • Thin skin :

–Covers most of the body

–Has only a few layers of dead surface cells

: • Thick skin – Covers the palms

– This skin is also hairy skin for the most part

of the hands and soles of the feet

–Has many layersof dead surface cells

Dermis

Source of blood and nutrients for the epidermis

•

• Composed of 2 layers: – “papillary”layer: • loose connective tissue

– “reticular”layer: • dense irregular connective tissue

• Directs the characteristics of the epidermis

DermisA. Overall Features

1. thick in some areas, thinner in others2. contains blood supply, nerves, glands, hair follicle

B. Papillary Layer (Region)1. loose connective tissue - much "elastin"2. dermal papillae cause ridges in the epidermis superficially3. Meissner's corpuscles - sense organ for deep touch4. small capillaries supply O + nutrients

C. Reticular Layer (Region)1. dense, irregular connective tissue "collagen"2. collagen fibers interlace in net-like fashion3. contains: adipose, hair follicle, nerves, glands4. subcutaneous layer attaches skin to tissue below

a. Paccinian corpuscles - sense pressure change

The Hypodermis

• AKA subcutaneous tissue or superficial fascia: – NOT a part of the “skin”

– Deep to the dermis

– Composed of loose connective tissue (primarily fat)

– Location of hypodermic injections

of the Epidermis Major Cell Types • Keratinocytes : – the most abundant cells

Melanocytes : – secrete the pigment melanin

Langerhans and dendritic cells :

– antigen-presenting cells

in the epidermis – synthesize and secrete keratin(a waxy hydrophobic protein that creates a water barrier)

– responsible for the “keratinized”epithelium

fibrous structural proteins. Keratin is the key structural material making up the outer layer of human skin. It is also the key structural component of hair and nails. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and insoluble and form strong unmineralized tissues

• protects the keratinocytefrom the sun

for the immune response (a type of macrophage)

– decrease in # with a sun tan!

lucid

granular

spiny

basal

Layers of the Epidermis and the Life Cycle of the Keratinocyteas it moves towards the surface:

Layers:

cornified

Layer of Epithelium

Epidermis (epithilial tissue)1. stratum corneum2. stratum lucidum – only palms and

soles – “clear”3. stratum granulosum4. stratum spinosom5. stratum basale

Basal

• Contains the stem cells

– Cells are attached to thebasement

– This is where mitosis

Layer

for keratinocytes – 1 layer thick – also contains melanocytes

occurs (about every 15-30 days)

• (psoriasis = ↑mitotic activity (turnover every 7 days)

membrane (by adherens junctions)

• hence the name of this layer

The Basal Layer meets the underlying Dermis

• Epidermal ridges (e.g.,fingerprints)

• Dermal papillae (tiny mounds): –strengthen attachment between epidermis and dermis

Spiny

adherens junctions

spines

Layer

• Contains 2–10 layers of keratinocytes attached to each other by many

• As the cells move away from the basal layer, they – begin to shrink • further from source of nutrition

– are still connected to adjacent cells by adhering junctions

– these connections look like

• hence the name of this layer

Stratum spinosum

Granular

amounts of keratin

Layer • Contains 2-5 layers of keratinocytes

• By this point in their life cycle, keratinocytes are producing significant

– which accumulates in and around the cells

– they now take on a granular appearance

• hence the name of this layer

• The cells are now far enough away from the source of nutrition that they are dehydrating and flatteningas well

Stratum granulosum

Lucid

dying keratinocytes

Layer • The clear (or “lucid”,

hence the name of this layer) layer

• Contains 1-5 layers of

• The cells are now very flat so it is difficult to see individual cells

• The cytoplasm appears homogeneous all the major organelles have died and degenerated

Stratum lucidum

Cornified

layers of dead cells

• Layers slough off

Layer

• Contains 10 -100’s of

– depending on whether thick or thin skin

• Basically composed of flat sheets (scales) of keratin

• (desquamate) here

Stratum corneum

Skin Color

– the pigments carotene :

melanin :

– and blood

• Skin color depends on:

• Orange-yellow pigment

• Found in orange vegetables

• Accumulates in epidermal cells and fatty tissuesof the dermis

• Can be converted to vitamin A

– and • Yellow-brown or black pigment • Produced by melanocytes in the basal layer

• Transferred to keratinocytes

• Protects DNA in nuclei of keratinocytes from sun (UV) damage

circulation (red blood cells) • Oxygenated red blood contributes to skin color:

– blood vessels dilate from heat, skin reddens

– blood flow decreases, skin pales

Melanocytes

Basal layer

More facts about skin color

• With a tan –pre-existing melanin darkens

–the rate of new melanin synthesis increases

Illness

• Jaundice :

• Cyanosis :

Vitiligo :

and Skin Color

– buildup of bileproduced by liver – yellow color

– Bluish skin tint – Caused by severe reduction in blood flow or

oxygenation

• – loss of melanocytes – loss of color

Accessory Structures

• Originate in the dermis

• Extend through the epidermis to skin surface: –hair

–nails

–exocrine glands

• sweat

• sebaceous

The sensory receptors in the skin are:cutaneous mechanoreceptors

Ruffini's end organ (sustained pressure)Meissner's corpuscle (changes in texture, slow vibrations)Pacinian corpuscle (deep pressure, fast vibrations)Merkel's disc (sustained touch and pressure)Free nerve endings (light touch)

Thermoreceptor (temperature)Nociceptor (noxious sensations)Chemoreceptor (sensitivity to chemicals)

Hair – protects and

insulates

– associated with touch receptors

• Functions:

• Composed of dead cells that are heavily keratinized

• Hair color is produced by melanocytes at the hair papilla

• Associated with: – Arrector pili: • smooth muscle

• causes hairs to stand up producing “goose bumps”

– Sebaceous glands

A Hair Shaft

External layer

Internal layer

Interesting hair facts

• Hairs grow discontinuously –There are periods of growth and periods of rest •Scalp: – growth periods may last many years

– rest periods average 3 months

• Hair in different regions of the body grows at different rates

Nails

•Nails protect fingers and toes :

and Nail Production

– composed of dead cells packed with keratin

– metabolic disorders can change nail structure

• Nail production occurs in a deep epidermal fold near the bone called the nail root

Interesting nail facts

• Transparency of the nail provides a useful window re amount of oxygen in the blood! –Indicator used during surgery • No nail polish!

Sweat glands : – most are merocrine

• found in both thick and thin skin

• secrete water and ions

– apocrine glands: • found in axillary, areolar

and anal regions only

• secrete apical portion of the cell with the water and ions

• associated with body odor

• active at puberty

Exocrine Glands •

glands:

Sebaceous oil glands:

whole cell is secreted

with hair follicles

puberty • lubricate

skin only

Exocrine Glands

•

– holocrine glands:

– associated with thin

– mainly associated

– begin to function at

and protect the epidermis

• inhibit bacteria so can produce the familiar odor of arm pits

  First Second(Superficial or Deep)

Third (Full Thickness)

Depth (howdeep the burn is)

Epithelium Epithelium and top aspects of the dermis Epithelium and dermis

How the wound looks No blisters; dry pink Moist, oozing blisters; Moist, white, pink, to red Leathery, dry, no elasticity; charred appearance

Causes Sunburn, scald, flash flame Scalds, flash burns, chemicals Contact with flame, hot surface, hot liquids, chemical, electric

Level of Pain (sensation)

Painful, tender, and sore Very painful Very little pain, or no pain

Healing Time Two to five days; peeling Superficial: five to 21 days. Deep: 21-35 days Small areas may take months to heal; large areas need grafting.

Scarring No scarring; may have discoloration

Minimal to no scarring; may have discoloration Scarring present

Burns

• First degree:• Includes only the outer layer of skin, the epidermis• Skin is usually red and very painful• Equivalent to superficial sunburn without blisters• Dry in appearance• Healing occurs in 3-5 days, injured epithelium peels

away from the healthy skin• Hospitalization is for pain control and maybe fluid

imbalance

Second Degree

• Second degree: Can be classified as partial or full thickness.

• Partial thickness– Blisters can be present– Involve the entire epidermis and upper layers of

the dermis– Wound will be pink, red in color, painful and wet

appearing– Wound will blanch when pressure is applied– Should heal in several weeks (10-21 days) without

grafting, scarring is usually minimal

Third Degree

• Third degree:• All layers of the skin is destroyed• Extend into the subcutaneous tissues• Areas can appear, black or white and will be

dry• Can appear leathery in texture• Will not blanch when pressure is applied• No pain

3rd degree full thickness

Fourth Degree• Full thickness

– Can be red or white in appearance, but will appear dry.

– Involves the destruction of the entire epidermis and most of the dermis

– Sensation can be present, but diminished– Blanching is sluggish or absent– Full thickness will most likely need excision & skin

grafting to heal– Extends into bone and muscle

This chart divides the body surface into

areas, each of which represents 9 percent. The "rule of nines" is

generally used for quick assessment of the total body surface area (TBSA) that has

been injured. In infants and small

children, the surface area of the head and neck is greater and

the lower extremity is smaller than an adult. Therefore, the Lund-Browder chart more

accurately determines the extent

of a burn.

Skin Cancer Facts

• 1/3 of all tumors are of the skin

• Rarely lethal (deadly) if diagnosed early: –Basal cell carcinoma: easily curable• derived from cells in the basal layer

–Squamouscell carcinoma: • derived from cells in the spiny layer

• Most serious and invasive tumors: –(Malignant) melanoma: • derived from melanocytes Any condition resulting in hair loss is called alopecia

• Actinic Keratosis: Precursor to Squamous Cell Carcinoma

• Rough, red or pink scaly patches on sun-exposed areas of the skin,usually <0.5cm in diameter

• Precurser lesion for squamous cell carcinoma (Squamous Cell Carcinoma)

• Up to 1% of these lesions can develop into a Squamous Cell Carcinoma

Ref:http://www.dermatology.ucsf.edu/skincancer/professionals/types.aspx

• Basal Cell Carcinoma :• Raised, pink, waxy bumps that may bleed

following minor injury• May have superficial blood vessels and a

central depression• Locally invasive• Rarely metastasizes• Organ transplant recipients have a 10-fold

higher risk for Basal Cell Carcinoma compared to the general population(2)

http://www.dermatology.ucsf.edu/skincancer/professionals/types.aspx

• Melanoma:• Neoplasm of pigment (melanin) producing cells• Brown or black skin lesion with irregularities in symmetry, border

and coloration• Prognosis dependent on depth of invasion• ~100,000 new cases of melanoma are diagnosed in the United

States each year– Only 4% of diagnosed skin cancer, but 77% of skin cancer related

deaths• Organ transplant recipients have a 3 to 4-fold higher risk for

melanoma compared to general population(12)– Melanoma accounts for ~6% of post transplant skin cancers in adult

transplant recipients(13)– Melanoma accounts for 12-15% of post transplant skin cancers in

pediatric organ transplant recipients(13)– Transplant recipients with a pre-transplant history of melanoma

have a high risk of recurrence (~20%)(14)

Quick Facts:

• The most readily cured type of cancer is basal cell carcinoma

• A condition involving absence or loss of hair is called alopecia

• Loss of skin color is called vitiligo• A single celled layer of squamous

epithelium is found lining blood vessels and alveoli and are called “endothelial” cells

Diabetes

• Exposure to high blood sugar levels damages the basement membrane of endothelial cells (sometimes called basal lamina). This may cause kidney disease and blindness

The 2 major components of skin are:

A. dermis and hypodermis

B. epidermis and dermis

C. dermis and subcutaneous layer

D. epidermis and hypodermis

Functions of the skin include:

A. temperature regulation

B. protection from infection

C. synthesis of vitamin D

D. sensory organ

E. all of the above

Thin skin is found in all of the following locations EXCEPT:

A. back

B. legs

C. arms

D. face

E. palms

The most abundant cell type of the epidermis is the:

A. melanocyte

B. Langerhanscell

C. fibroblast

D. keratinocyte

E. basal cell

The layer of skin in which keratinocytes divide is the:

A. cornified layer

B. basal layer

C. granular layer

D. spiny layer

E. lucid layer

The layer of skin in which keratinocytes slough off is the:

A. cornified layer

B. basal layer

C. granular layer

D. spiny layer

E. lucid layer

Most of your sweat glands:

A. release only water and ions

B. release a part of the cell with the water and ions

C. release the whole cell with the water and ions

D. release oil

E. are found in thick skin only

Skin color is determined by:

A. melanin

B. carotene

C. blood

D. none of the above

E. all of the above

What are the 5 layers of the epidermis?

• Be sure that you can name them in order and how changes occur which actually forms these layers.

What is the nature of a fingernail?

• Know the features of the fingernail• Know the features of a hair• Based on the rule of 9s, what percent of the

body surface is occupied by the skin of the trunk?

• What is meant by 1st degree, 2nd degree and 3rd degree burns?

• What are the three main types of skin cancer and what are their features?

Damage to the basal lamina due to untreated diabetes may lead to kidney failure and what other

malady?• You have to come up with the answer!