The Integumentary System

Group 4

Integumentary System

• is the organ system that protects the body from damage, comprising the skin and its appendages.

•  the largest of the body's organ systems.•  this system accounts for about 12 to 15 % of total

body weight.• composed of 3 major layers of tissue:

the epidermis, dermis, and hypodermis.• The study of the skin is Dermatology

Skin

• Layers of the skinConsists of 3 main layers:

EpidermisDermisHypodermis

Epidermis

• Outermost or the epidermal layer• Composed of stratified squamous, keratinized cell

epithelial cells• Held together by highly convoluted, interlocking

cellular links called desmosomes • Is the thickest where it receives the most abrasion and

weight (on the palms of the hand and the soles of the feet)

• There are 5 layers of the epidermis

Epidermis

• The 5 layers of the epidermis (from outermost to deep):Stratum CorneumStratum LucidumStratumGranulosumStratum SpinosumStratum Germinativum/Basale

Epidermis

• Stratum CorneumHorny or leathery layerForms the outermost layer of the epidermis Consist of dead cell converted to proteinMany layers thickThe thickness of this layer is determines by the

amount of stimulation on the surface by abrasion or weight bearing.

Epidermis

• Stratum LucidumClear layerLocated directly beneath the s. corneumOnly one or two cell layers thick Cells are transparent and flat

Epidermis

• Stratum GranulosumGranular layerConsists of two to three layers of flattened cellsGranules tend to accumulate in these cells,This layer is very active in keratinizationIn this layer, the cells lose their nuclei and become

compact and brittle

Epidermis

• Stratum SpinosumSpiny or prickly layerConsists of several spiny-shaped cellsIn this layer, desmosomes are still quite prevalent

Epidermis

• Stratum GerminativumInnermost and most important or the regenerative layerContains the only cells capable of dividing by mitosisThe epidermis will regenerate itself only so long as the s.

germinativum remains intactHas basal layer called Stratum Basale which rests on the

basement membraneContains melanocytes which produces a pigment called

melanin

Dermis

• Also known as the corium • Lies directly beneath the epidermis• Often referred to as the “true skin”• Composed of dense CT with tough white collagen

fibers and yellow elastin fibers• Blood vessels, nerves, lymph vessels, sweat glands,

hair follicles, sebaceous glands are all embedded in this layer

• Can be divided into two portions

Dermis

• Two portions:Papillary portionReticular Portion

Dermis

• Papillary portionArea adjacent to the epidermis

• Reticular PortionFound between the papillary portion and the fatty

subcutaneous tissue beneath

Hypodermis

• Also called the hypoderm, subcutaneous tissue, or superficial fascia

• Lowermost layer of the integumentary system

• It is in this layer where hypodermic injections are given

• Attaches the reticular layer to the underlying organs

Functions

• Thermoregulation• Protection• Attachment site for sensory receptors/Sensation• Excretion• Storage and synthesis

Functions• Thermoregulation

Normal body temp. is regulated by blood vessel dilation and constriction in the dermis of the skinHigh temperature

Dilate surface blood vessels Sweating

Low temperature Surface vessels constrict shivering

Functions• Protection

Physical AbrasionDehydrationUltraviolet radiationsPrevents passage of harmful chemical agentsBody’s first line of defenseKills most bacteria and microorganisms that make contact

with our skin (acid mantle)Lipid content of the skin inhibits excessive loss of water

and electrolytes through the skinMelanin protects us from harmful uv rays of the sun

Functions

• Attachment site for sensory receptors/SensationMechanoreceptors - responds to mechanical

pressure or distortion.There are 4 main types of mechanoreceptors:

Pacinian corpusclesMeissner's corpusclesMerkel's discsRuffini endings

Functions

• Mechanoreceptors:Pacinian Corpuscle

-or Lamellar corpuscle

-they are nerve endings in the skin, responsible for sensitivity to vibration and deep pressure.

-large encapsulated endings located in the subcutaneous tissue.

-sense transient disturbances at high frequencies.

-rapid adapting

-located at the deep subcutaneous tissue

Functions

• Mechanoreceptors:Meissner’s Corpuscle

-or Tactile Corpuscle

-they are a type of nerve ending in the skin that is responsible for sensitivity to light touch and vibration.

-rapid adapting

-located superficially

Functions

• Mechanoreceptors:Merkel’s disc

-or Merkel nerve endings

-play a major role in the static discrimination of shapes, edges, and rough textures.

-slow adapting

-most sensitive of all the 4 mechanoreceptors

-located superficially

Functions

• Mechanoreceptors:Ruffini ending

-or Bulbous Corpuscle or Ruffini Corpuscle

-respond to sustained pressure

-also a thermoreceptor

-slow adapting

-located in the deep layers of the skin

Functions

• ExcretionWhere salts and urea exits during sweatingExcretes also dead cells

Functions

• Storage and synthesisAids in the absorption of CaVitamin D synthesis through exposure to

ultraviolet lightStores lipids and water

Accessory structure of the skin

• Hair

• Nails

• Sebaceous glands

• Sweat glands

• Ceruminous glands or wax

• Mammary glands

Accessory structure of the skin

• Hairsmain characteristic of all mammalsCovers the entire part of the body except the palms

of the hands and the soles of the feetEpidermal growths that function in protectionShaft, root, and follicleEach individual hair is composed of three parts

Accessory structure of the skin

• Three layers of the hair:CuticleCortexMedulla

Accessory structure of the skin

• CuticleOutermost portionConsists of several layers of overlapping scale-like

cells

Accessory structure of the skin

• CortexPrincipal portion of the hairIts cells are elongated and united to form flattened

fibers

Accessory structure of the skin

• MedullaMiddle or central part of the hairComposed of cells with many sides which

frequently contain air spaces

Accessory structure of the skin

• Parts of the hair:Hair shaftRootHair follicle

Accessory structure of the skin

• Hair shaftVisible portion of the hair

• RootFound in an epidermal tube called the hair follicle

• Hair follicleMade of an outer CT sheathWhere production of hair occursBundles of smooth muscle fibers that make up the

arrector pili muscle

Nails

• Plates of highly packed, keratinized cells

• Protection, scratching, & manipulation

• Formed by cells in nail bed called the matrix

• 1 mm / week

• Has 4 parts

• Fingernails grow faster than toenails

• As we age, the rate of the nail growth, slows

Nails

• Parts:Nail matrixNail rootEponychiumLunulaNail bodyFree edgeNail grooveNail bed

Nails

• Nail MatrixThe tissue which the nail protectsPart of the nail bed that rests beneath the nail and

contains nerves, blood vessels and lymph vesselsResponsible for producing the nail itself

• Nail rootPart of the nail attached to the nail bedIt is the bas of the nail underneath the skin

Nails

• EponychiumOr cuticleIs a stratum corneum that extends out over the

proximal end of the nail body

• LunulaWhite crescent at the proximal end each nailThe size varies from person to person and

sometimes from nail to nail due to genetic factors

Nails

• Nail bodyVisible part of the nail

• Free edgeanterior margin of the nail bodycorresponds to the abrasive or cutting edge of the

nail

Nails

• Nail grooveOr nail foldare the cutaneous slits into which the lateral

margins are embedded.

• Nail bedFrom which the nail growsSkin beneath the nail

Nail groove

Sebaceous Glands

• Usually connected to hair follicles

• Holocrine glands

• Fats, cholesterol, proteins, salts, and cell debris

• Moistens hair and waterproofs skin

Sweat (sudoriferous) glands

Eccrine sweat glands

Merocrine glands

Water, salt, wastes

Function is to cool the body (also nervous)

Apocrine sweat glands

Larger, merocrine glands

Associated with hair follicles

More viscous – fatty acids and proteins

Odor occurs when broken down by bacteria

Ceruminous glands

Modified sudoriferous glands

Secrete cerumen (ear wax)

Mammary glands

Secrete milk

Skin color

• Genetic factorsSame number of melanocytesAlbinism

• Environmental factorsUv light or x-rays

• Physiological factors

Amount of blood

Amount of oxygen

CyanosisCarotene accumulationJaundice – liver disorder

Skin Diseases

• Albinism-also called achromia, achromasia, or achromatosis, is a congenital disorder characterized by the complete or partial absence of pigment in the skin, hair and eyes due to absence or defect of tyrosinase, a copper-containing enzyme involved in the production of melanin

Skin Diseases

• Skin Allergies

Skin Diseases

• Skin Cancer-Skin cancer is a condition caused by exposure to certain light rays from the sun and from tanning beds

-this cancer has been on the rise in the general population for many years and has emerged as the leading type of cancer in men.

Wound healing

• InflammationBlood vessels dilate and become permeable

Heat, redness, swelling and pain

• Shallow cutsEpithelial cells migrateContact inhibition

Deeper wounds

• Inflammatory phaseFibrin forms clot

• Migratory phaseFibroblasts make granulation tissue

• Proliferative phase

• Maturation phase

• Scars – hypertrophic scar keloid

Burns

• First degree or partial thickness burnOnly epidermis is damagedErythema, mild edema, surface layer shedHealing – a few days to two weeksNo scarring

• Second degree- deep partial-layer burnDestroys epidermisBlisters form Healing depends on survival of accessory organsNo scars unless infected

• Third degree or full-thickness burnDestroys epidermis, dermis and accessory organs

of the skinHealing occurs from margins inwardSkin grafting may be needed

AutograftHomograft

• Rule of Nines