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Integumentary System:Essential Learning(s)

Skin and Its Tissues

List the general functions of the skin.

Describe the structure of the layers of skin.

Summarize the factors that determine skin color.

Accessory Structures of the Skin

Describe the accessory structures associated with the skin.

Explain the functions of each accessory structure of the skin.

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Integumentary System:Essential Learning(s)

Regulation of Body Temperature

Explain how the skin helps regulate body temperature.

Healing of Wounds and Burns

Describe the events that are part of wound healing.

Distinguish among the types of burns, including a description of healing with each type.

Lifespan Changes

Summarize lifespan changes in the integumentary system.

Levels of Organization

Subatomic particles

Atom

Molecule

Macromolecule

Organelle

Cell

Tissue

Organ

Organ system

Organism

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Introduction:Integumentary System

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• Two or more kinds of tissues grouped together and performing specialized functions constitutes an organ.

•The integumentary system consists of a major organ, skin, and many epidermal derivatives (accessory struc)which include hair follicles, sebaceous glands, sweat glands, and nails.

What is the function of the skin? What does it do?

Skin and Its FunctionsProtection:

Physical barriera. From water lossb. From injury c. From chemicals and microorganismsChemical barriera. ph of 5 – 6b. Prohibits microbial growthBiological barriera. Langerhan’s cells (epidermis) – function

with leukocytes to trigger immune

reactionsb. Macrophages and mast cells (dermis)

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Skin and Its Functions

Protection: Surface film – produced by the mixing of residue and secretions from sweat and sebaceous glands with epithelial cells constantly being cast off from the epidermis

Functions: Antibacterial and antifungal activityLubricationHydration of skin surfaceBuffering of caustic irritantsBlockage of many toxic agents

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Skin and Its FunctionsExcretion: (minimal, most through kidneys!)

through sweat - urea and uric acid

Regulation of Body Temperaturerecall negative feedback mechanism from Ch. 1

Cutaneous SensationLight touch detection = tactile (Meissner’s) corpuscles

a. egg-shapedb. Located in dermal papillaec. populate areas in the fingertips, palms, soles,

eyelids, tip of the tongue, nipples, clitoris, and tip of penisPressure detection = lamellated (Pacinian) corpuscles

a. Onion-shapedb. located in deep dermis and subcutaneous

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Skin and Its Functions

Vitamin D synthesis:

UV rays in sunlight activate its synthesis

Vitamin D is required for bone homeostasis Blood Reservoir:

The dermis houses about 10% of the body’s blood vessels

Skin only requires 1 – 2% of the body’s blood

Immunity:

Langerhan’s cells (macrophages)

interact with T-helper cells in immune responses 9

Layers of Skin

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• Epidermis - outermost layer of cells

• Dermis - inner layer

• Subcutaneous layer - adipose tissue

• A.k.a hypodermis• Beneath dermis

Stratifiedsquamousepithelium

Dense irregularconnectivetissue

Adipose tissue

Epidermis

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(a)

Hair shaft

Epidermis

Hair follicle

(b)

Sebaceous gland

Dermis

Sweat

Epidermis

Dermis

Hair shaft

Sweat gland pore

Capillary

Stratum corneum

Stratum basale

Dermal papilla

Arrector pili muscle

Lamellated (Pacinian) corpuscle

Basement membrane

Sebaceous gland

Hair follicle

Sweat gland

Nerve cell process

Adipose tissue

Blood vessels

Muscle layer

Sweat gland duct

Subcutaneouslayer

T Tactile (Meissner’s) corpuscle

• Structure = keratinized stratified squamous epithelium

•Function = Protection (keratin) prevents water loss; prevents injury by penetration; prevents microbe/chemical entry

•Pigment = melanindetermines skin colorproduced by melanocytes in stratum basale

o genetic factorso environmental factorso physiological factors

b: © Victor Eroschenko

Epidermis

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There are five (5) layers of the epidermis:• Stratum corneum – outermost layer• Stratum lucidum (only in thick skin – palms, soles)• Stratum granulosum – 3-5 layers of flattened granular cells (keratin)• Stratum spinosum - many layers of spiky cells w/ large nuclei• Stratum basale – innermost layer (directly above basement mem)

* Together the spinosum and basale make up the stratum germinativum

Stratum corneum

Stratum lucidum

Stratum granulosum

Stratum spinosum

Stratum basale

Basementmembrane

Dermis

Dermal papilla

(a) (b)

EpidermisStructure = keratinized stratified squamous epitheliumFour distinct layers

each determined by the extent of keratinization in the epithelial cells:

Stratum corneum = outermost layer dead epithelial cells filled with the protein keratin

Stratum lucidum = translucent layer separating s. corn & s. granextra layer only in thick skin of soles & palms

Stratum granulosum = composed of 3-5 layers of flattened granular cells (filled w/ keratin granules)

Stratum spinosum = composed of many layers of “spikey” cells with large nuclei

Stratum basale = innermost layer; directly above basement m.singe row of mitosing cuboidal cells & melanocytes

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Epidermis

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Genetic Factors• Varying amounts of melanin• Varying size of melanin granules• Albinos lack melanin

Environmental Factors• Sunlight• UV light from sunlamps• X-rays• Darkens melanin

Physiological Factors• Carotene may accumulate in

s. corneum = orange• Hb in dermal b vessels = pink• Lack of Hb = blue (cyanosis)• Inability to breakdown Hb (liver problem) = yellow

Pigment = melanina) determines skin colorb) produced by melanocytes in s. basale

Heredity and environment determine skin color

Dermis

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Ex. nails, hair follicles and skin glands

Functions: A. nourishment of epidermis B. provides strength/flexibility

inner layer of skin; binds epidermis to underlying tissues

Structure: A. two distinct layers

1) papillary layer2) reticular layer

B. houses epidermal derivativesor accessory structures

(a)

Sweat

Epidermis

Dermis

Hair shaft

Sweat gland pore

Capillary

Stratum corneum

Stratum basale

Dermal papilla

Arrector pili muscle

Lamellated (Pacinian) corpuscle

Basement membrane

Sebaceous gland

Hair follicle

Sweat gland

Nerve cell process

Adipose tissue

Blood vessels

Muscle layer

Sweat gland duct

Subcutaneouslayer

Tactile (Meissner’s) corpuscle

Accessory structures of the Skin Nails:

1. structure: epithelia undergoing keratinization

(mitotically active in lunula)

2. functions:

a. manipulation

b. protection of ends of digits Hair follicles:

1. structure:

a. root or base in deep dermis

b. follicle throughout dermis

c. shaft in epidermis extending beyond the surface

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Accessory structures of the Skin Hair follicles: cont

2. Keratinization

a. cell are epithelium

b. cells in root = mitotically active

c. cells in follicle = maturing & accum. keratin

d. cells in epidermis = dead epith. cells; full of keratin

= exposed hair or hair shaft

3. Pigment = melanin

a. albinism = lack of melanin

b. red hair = trichosiderin

4. Arrector pili muscle = bundle of smooth muscle assoc. w/

every hair follicle

a. causes hair to stand on end when frightened or cold

= “goose bump”

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Accessory structures of the Skin Skin glands:

1. Sebaceous glandsStructure:

a. holocrine gland (simple cuboidal epith.)b. assoc w/ every hair folliclec. secretion = sebum (ie. oil) fat and cell

materialsebum is secreted into hair follicle

Function:a. sebum keeps skin/hair soft, pliable, &

waterproofDisorders:

a. acne (hypersecretion sebum;ducts clog & inflame)

b. seborrhea (hyperprod of sebum; oily scales)

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Accessory structures of the Skin Skin glands: cont

2. Sweat glands & sudoriferous glands * Two types (based on glandular secretion)a. Merocrine (eccrine) glandsStructure: coil in deep dermis; duct in dermis; pore at surfaceCharacteristics: respond to elevated temp/exercise; no odor in secretion; function throughout life; not assoc w/ hair follicleLocation: forehead; neck; backSecretion: water + salts + waste (urea/uric acid)

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Accessory structures of the Skin Skin glands: cont

2. Sweat glands & suboriferous glandsb. Apocrine glands Structure: ducts terminate into fair follicles Characteristics: respond to stress/emotions; odor in secretion;

function at puberty/continue thru life; assoc w/ hair follicles

Location: armpits & groin Secretion: sweat (as above) + oil + cellular debris Modified Apocrine glands: ceruminous gland=ear wax mammary

gland=milk

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Dermis

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1) Papillary layer (20%) a. superficial = below epidermis b. loose areolar CT c. dermal papillae here

form fingerprints in thick skin d. Meissner’s corpuscles

- light touch receptor

2) Reticular layer (80%) a. collagen/elastic/reticular

fibers = strength & resiliency b. cleavage, tension or

Langer’s lines are here c. Lamellated (Pacinian) corpuscles

– deep pressure receptors

Two layers of the dermis:

(a)

Papillary layer

Reticular layer

Subcutaneous Layer

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Hypodermis

Structure:Loose connective

tissue and adipose tissue Function:

Insulates

Major blood vessels present(a)

Sweat

Epidermis

Dermis

Hair shaft

Sweat gland pore

Capillary

Stratum corneum

Stratum basale

Dermal papilla

Arrector pili muscle

Lamellated (Pacinian) corpuscle

Basement membrane

Sebaceous gland

Hair follicle

Sweat gland

Nerve cell process

Adipose tissue

Blood vessels

Muscle layer

Sweat gland duct

Subcutaneouslayer

Tactile (Meissner’s) corpuscle

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Hair Follicles

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• Epidermal cells

• Tube-like depression

• Extends into dermis

• Three (3) parts:• Hair root• Hair shaft• Hair papilla

• Dead epidermal cells

• Melanin• Arrector pili muscle

(a)

Hair shaft

Pore

Hair root(keratinizedcells)

Arrector pilimuscle

Sebaceousgland

Hair follicle

Region ofcell division

Hair papilla

Eccrinesweat gland

Dermal blood vessels

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Nails

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Function: protective covering

Structure: Three (3) parts:

Nail plate

Nail bed

Lunula

Nail bed Nail plateLunula

Sebaceous Glands

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Usually associated w/ hair follicles

Holocrine glands

Secrete sebum (oil)

Absent on palms and soles

Hair

Sebaceousgland

Hair follicle

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© Per H. Kjeldsen

Sweat Glands

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• A.k.a sudoriferous glands

• Widespread in skin

• Originates in deeper dermis or hypodermis

• Eccrine glands

• Apocrine glands

• Ceruminous glands

• Mammary glands

Dermalpapilla

Sebaceousgland

Duct

Hair shaft

Hairfollicle

Eccrinesweatgland

Apocrinesweatgland

Pore

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Regulation of Body Temperature

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1. Regulation of body temperature is vitally important because even slight shifts can disrupt metabolic reactions * Heat production is mostly a by-product of cellular metabolism

2. Heat loss controlled by regulating dermal blood flow a. vasodilation – increases dermal blood flow = incr. heat loss b. vasoconstriction – decreases dbf = decr. Heat loss 3. Four methods of heat loss

a. radiation – most heat loss; infrared heat rays move from

area of high heat (blood) to low heat (environ)

b. conduction – less heat loss; heat moves by phys contact

c. convection – heat loss to surrounding air; incr. as air moves

d. evaporation – heat loss varies; if heat incr. sweating incr.

lose heat by sweat evaporating on skin

Regulation of Body Temperature 4. Low body temperature requires heat loss to be

minimized

a. the hypothalamus signals for sweating to decrease

(decreasing heat loss by evaporation) and dermal

vasoconstriction (decreasing heat loss by radiation)

b. usu. brings body temp back to normal 5. If body temp remains low (after the above action)

a. heat must be produced

b. shivering occurs and the tiny muscle contrations

involved produce heat28

Regulation of Body Temperature Problems in Temperature Regulation

1. Hyperthermia = elevated body temperature

requires heat to be dissapated

a. Two common causes:

1. humid air decreases evaporation

2. air temp exceeds body temperature

heat is gained/ not lost

2. Hypothermia = low body temperature

a. very dangerous is core temp. drops below 94 F

b. limbs can withstand 65 F because they contain

no vital organs

c. intentional during some surgical procedures

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Regulation of Body Temperature

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If body temperaturecontinues to drop,control center signalsmuscles to contractinvoluntarily.

too high

too low

Normal bodytemperature37°C (98.6°F)

Control centerHypothalamusdetects the deviationfrom the set point andsignals effector organs.

Control centerHypothalamusdetects the deviationfrom the set point andsignals effector organs.

StimulusBody temperature risesabove normal.

EffectorsDermal blood vesselsdilate and sweat glandssecrete.

ResponseBody heat islost to surroundings,temperature drops towardnormal.

EffectorsDermal bloodvessels constrictand sweat glandsremain inactive.

EffectorsDermal bloodvessels constrictand sweat glandsremain inactive.

ResponseBody heat is conserved,temperature rises toward normal.

StimulusBody temperaturedrops below normal.

ReceptorsThermoreceptorssend signals to thecontrol center.

ReceptorsThermoreceptorssend signals to thecontrol center.

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Healing of Wounds and Burns

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A. Cuts1. Epidermal cuts are closed by increased cell

division in the stratum basale2. Deep cuts involve blood vessel damage resulting in: a. inflammation b. blood clotting c. scab formation d. fibroblast infiltration e. scab falls off f. scar may or may not form

B. Burns1. superficial partial- thickness burns (1st degree)

a. epidermis onlyb. reddening due to increased blood

flowc. mild paind. common in sunburne. heals in a few days to 2 weeks

Healing of Wounds and Burns B. Burns (cont)

2. Deep partial-thickness burns (2nd degree)

a. epidermis & some dermal damage

b. reddening and blistering (blood vessel damage)

c. moderate pain

d. common to physical contact w/ hot objects

e. heals in 2-6 weeks w/0 scars unless infected

3. Full-thickness burns (3rd degree)

a. epid., derm., and subcutaneal damage

b. dry, leathery tissue w/ red or black color

c. severe pain

d. caused by prolonged heat or chemical contact

e. healing rarely occurs due to lack of surviving skin

cells; grafts needed; usually extensive scarring

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Healing of Wounds and Burns B. Burns…cont

3. Full-thickness burns (3rd degree)f. autograft – transplant from

undamaged area of selfg. homograft – temporary transplant

from cadaver4. Body surface affected

a. estimated by “rule of nines”b. important for determining

treatment/prognosis

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(a) (b)

(f) (g)

(c) (d) (e)

Scartissue

Fibroblasts

Scartissue

Blood cells

Site of injury

Scab

Bloodclot

Scab

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Rule of Nines for Adults

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Anteriortrunk18%

Posteriortrunk18%

Anterior upperextremities 9%

Posterior upperextremities 9%

Posterior lowerextremities 18%

Perineum 1%

Anterior andposterior upper

extremities18%

Anterior andposterior lower

extremities36%

100%

Anterior andposterior trunk

36%

Anterior and posterior head and neck9%

Anterior headand neck 41/2%

Posterior headand neck 41/2%

Anterior lowerextremities 18%

9% 9% 9% 9%

41/2%

41/2% 41/2% 41/2% 41/2%

41/2%

Lifespan Changes A. Aging skin exhibits:

1. wrinkling

a. some individuals choose “botox” injections to temp

reduce wrinkles

2. sagging

3. age spots or liver spots

B. Efficient regulation of body temperature declines w/ age

1. number of sweat glands changes

2. capillary beds in the skin shrink

C. Synthesis of vit. D declines as skin ages, which affects

skeletal health = ex. osteoporosis36

Lifespan Changes

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• Skin becomes scaly• Age spots appear• Epidermis thins• Dermis becomes reduced• Loss of fat• Wrinkling• Sagging• Sebaceous glands secrete less oil

• Melanin production slows• Hair thins• Number of hair follicles decreases• Nail growth becomes impaired• Sensory receptors decline• Body temperature unable to be controlled• Diminished ability to activate Vitamin D