integumentary system skin, hair, nails, associated glands & structures skin is sometimes called...

Integumentary System

Skin, Hair, Nails, Associated Glands & Structures

Skin is sometimes called the cutaneous membrane.

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Skin & Accessory Structures

• Skin– large waterproof covering– UV light and chemical protection– Covers 3000 square inches of the body– Weighs 6 lbs– Helps regulate body temperature

• Accessory structures– hair, nails, glands

Skin Functions

• Protects deeper tissues from:– Mechanical damage– Chemical damage– Bacterial damage– Thermal damage– Ultraviolet radiation– Desiccation

Skin Functions

• Aids in heat regulation• Aids in excretion of urea and uric acid• Synthesizes vitamin D

Meissner’s CorpuscleA Mechanoreceptor of Touch

5.

Epidermis

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General Characteristics

• Stratified, squamous, keratinized, epithelium

• Held together by desmosomes (allows the flexibility of the skin)

• Thickest on the palm and soles• Thinnest over the ventral surface of

trunk

Skin Structure

• Epidermis – outer layer– Stratified squamous

epithelium– Often keratinized

(hardened by keratin)• Dermis

Figure 4.3

Layer of Epidermis

• Stratum corneum– Shingle-like dead cells

• Stratum lucidum– Occurs only in thick skin

Layer of Epidermis

• Stratum granulosum• Stratum spinosum• Stratum basale

– Cells undergoing mitosis– Lies next to dermis

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The Stratum Corneum

• Outermost layer• Dead, keratinized cells• Barrier to light, heat, chemicals,

microorganisms• “leathery” layer

Stratum Corneum

• Consists of about 20% water• Constantly losing this layer• Thickness depends on use (hands, soles)• A thick Callus can form from heavy use• Abrasions on the foot produce Corns

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The Stratum Lucidum

• One to two cell layers thick• Flat and transparent• Difficult to see

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The Stratum Spinosum

• Several layers of spiny-shaped cells• Desmosomes prevalent

– Desmosomes: interlocking cellular bridges

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The Stratum Granulosum

• Two or three layers• Flattened cells• Active keratinization• Lose nuclei• Compact and brittle

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The Stratum Germinativum

• Deepest and most important layer• Rests on basement membrane• Lowermost layer called stratum basale• New cells produced here (mitosis)• This layer must remain intact so the

epidermis will regenerate

Stratum Germinativum

• Melanocytes - produce melanin• Produces skin color• Irregularly shaped• All races have the same number of

melanocytes, but specific genes that determine the amount of melanin produced

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Skin Structure

Figure 4.4

• Non-vascularized• The lowermost cells divide by mitosis• Keratinization occurs as new cells rise

– cells move to surface, lose water and nuclei change

– Filled with keratin (protein)

• Composed of five layers

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The Dermis

True Skin (Corium)

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Divisions of the Dermis

• Papillary– adjacent to the epidermis

• Reticular– between papillary and subcutaneous

• Subcutaneous (hypodermis)– layers of fat below the dermis– Where you get hypodermic injections

Dermis• Two layers– Papillary layer

• Projections called dermal papillae• Pain receptors• Capillary loops

– Reticular layer• Blood vessels• Glands• Nerve receptors

Hypodermisaka

Subcutaneous Layer

• Deep to dermis– Not part of the skin– Anchors skin to underlying organs– Composed mostly of adipose tissue

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Structures Found in Dermis

• The following are all found here in the dermis– Blood and lymph vessels– Nerves– Muscles– Glands– Hair follicles

Sebaceous Glands

– Produce oil (Sebum)• Lubricant for skin• Kills bacteria

– Most with ducts that empty into hair follicles

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Sebaceous Glands

– Brushing hair brings more out– secretion controlled by endocrine system– Increases at puberty

• Causes acne• Later on, it decreases and causes dry skin

Suderiferous Glands

• Sweat glands– Widely distributed in skin– Two types

• Eccrine– Open via duct to pore on skin surface

• Apocrine– Ducts empty into hair follicles

Suderiferous Glands

• Sweat– most numerous in palms and soles

• 3000 per square inch on palms

– Not found on lips or male genitalia– sweating helps cool the body

• Same materials as blood• Odorless (smell is bacteria)

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Sweat and Its Function

• Composition– Mostly water– Some metabolic waste– Fatty acids and proteins (apocrine only)

• Function– Helps dissipate excess heat– Excretes waste products– Acidic nature inhibits bacteria growth

• Odor is from associated bacteria

Normal Skin Color Determinants

• Melanin– Yellow, brown or black pigments

• Carotene– Orange-yellow pigment from some vegetables

• Hemoglobin– Red coloring from blood cells in dermis capillaries– Oxygen content determines the extent of red

coloring

Melanin

• Pigment (melanin) produced by melanocytes• Color is yellow to brown to black• Melanocytes are mostly in the stratum basale• Amount of melanin produced depends upon

genetics and exposure to sunlight

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Dermis

• Pink tint of light skinned individuals is a result of the blood vessels here

• When you get embarrassed, blood vessels here dilate and causes blushing

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•Hair

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Hair

• One main characteristic of mammals• Covers most of the surface of the body• Three parts - cuticle, cortex, medulla

– Cuticle• Outermost part

– Cortex• Principal portion of hair• Contain fibers that determine hair color

– Medulla – central part of the hair

• Shaft - visible portion• Root - hair follicle

– Has an outer connective tissue sheath

• Arrector pili - smooth muscle– Causes goose bumps– Involuntary

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Hair Characteristics

• Growth– hair follicle– cycles of growth and rest– Begins in the hair bulb (blood vessels to nourish)– Hair loss occurs because new hair pushes old hair

down – baldness occurs because the follicle is lost too– The cycles depend on hair:

• Scalp hair grows for 3 years and rests for 1 or 2

Hair

• Texture - straight, curly, or tightly curly– Based on keratin in hair

• Color - based on complex genetic factors– Gray hair occurs due to a loss of pigment in

the cortex

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Appendages of the Skin• Hair– Produced by hair

bulb– Consists of hard

keratinized epithelial cells

– Melanocytes provide pigment for hair color

Figure 4.7c

Hair Anatomy• Central medulla• Cortex surrounds

medulla• Cuticle on outside of

cortex– Most heavily keratinized

Figure 4.7b

Nails

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Nails

• Modified epidermal cells– Composed of very hard keratin

• Lunula - white crescent– Caused by air mixed in the keratin

• Body - visible portion• Root - covered by skin• Growth occurs from the nailbed

– Grows about 1mm per week– Cuticle extends over the proximal end of the nail body– Fingernails grow faster than toe nails

Nails

– Scale-like modifications of the epidermis• Heavily keratinized

– Stratum basale extends beneath the nail bed• Responsible for growth

– Lack of pigment makes them colorless

• Free edge• Body• Root of nail• Eponychium –

proximal nail fold that projects onto the nail body

Figure 4.9

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Miscellaneous and

Pathology

Homeostatic Imbalances

• Burns– Tissue damage and cell death caused by heat,

electricity, UV radiation, or chemicals– Associated dangers

• Dehydration• Electrolyte imbalance• Circulatory shock

Rule of Nines

• Way to determine the extent of burns

• Body is divided into 11 areas for quick estimation– Each area represents

about 9%

Figure 4.11a

Severity of Burns

• First-degree burns– Only epidermis is damaged– Skin is red and swollen

• Second degree burns– Epidermis and upper dermis are damaged– Skin is red with blisters

• Third-degree burns– Destroys entire skin layer– Burn is gray-white or black

Critical Burns

• Burns are considered critical if:– Over 25% of body has second degree burns– Over 10% of the body has third degree burns– There are third degree burns of the face, hands, or

feet

Skin Cancer

• Cancer – abnormal cell mass• Two types

– Benign• Does not spread (encapsulated)

– Malignant• Metastasized (moves) to other parts of the body

• Skin cancer is the most common type of cancer

Skin Cancer Types• Basal cell carcinoma

– Least malignant– Most common type– Arises from statum basale

• Squamous cell carcinoma– Arises from stratum spinosum– Metastasizes to lymph nodes– Early removal allows a good chance of cure

Skin Cancer Types

• Malignant melanoma– Most deadly of skin cancers– Cancer of melanocytes– Metastasizes rapidly to lymph and blood vessels– Detection uses ABCD rule

ABCD Rule

• 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