The Integumentary System

The Integumentary System1 organ + accessory organsSkin is an organAccessory organsHair folliclesSebaceous glandsSweat glandsnails

2Like other organsSkin is made of many tissuesHas many functions

Stratified squamous epithelial, simple cuboidal around the glands, dense irregular connective tissue in dermal layer along with adipose tissues3Cutaneous MembraneAnother name for skinWhat are the other two epithelial membranes?Hint: end of chapter 5

SerousMucousSerous membranes line cavities that do not open to the outside of the body. They secrete serous fluid. Mucous membranes secrete mucous and DO open to the outside world.4FunctionsProtectionExcretionMaintain homeostasisSensory reception Blood reservoirimmunity

Memorize this!!8-10% of blood is there.Fatty acids in sebaceous glands and bacteria in skin flora inhibit growth of fungi and other bacteria. Lysozymes in the sweat & Langerhands cells52 Distinct Regions

EpidermisDermisEpidermis is keratinized. Dermis has keritinized cells along the edge of the hair follicles, glandular epithelium, dense irregular CT, smooth muscle tissue, nervous tissue (corpuscles) and blood vessels.Subcutaneous layer, or hypodermis is below the skin.6FunctionsPhysical BarrierWater lossInjuryChemicals & microbes

Chemical BarrierpH of 5-6Prevents microorganism growth

Antibiotic peptides along with sweat and sebum in the skin make it difficult for foreign microorganisms to live there. The resident microbes fight invaders.People with excema or other sensitive skin conditions have to be really careful about maintaining proper pH8Biological BarrierLangerhans cellsMacrophages and mast cells

Langerhans cells are in the epidermis. These cells originate in the bone marrow and migrate to the epidermis. There are about 700 to 800 per square mm in your epidermis. They activate dormant T-helper cells to fight infections. When they are done with a fight, they are removed by the lymphatic system.Macrophages consume invaders by phagocytosis. Mast cells give us allergy symptoms, but they are also an important part of our immune system. They look like white blood cells.Tattoos are just pigments captured in fibroblasts in the dermal layer. However, as the skin tries to recup from the wounds of tattooing, these phagocytotic cells also eat the pigment and carry it away fading, moving ink.9ExcretionUrea waste product from metabolizing protein (colorless, odorless). Excreted in sweat and urine. Used in cosmetic products.Uric acid (guano) different chemical compound. Leads to kidney stones. Only excreted through urine.

99%waterMinimal compared to kidneysKidneys do the heavy lifting in excreting liquids, but skin performs a small part of it too.10Regulate Body TemperatureToo hot? Too cold?

RADIATION and DILATION

Vessels constrict and sweating stopsHeat detected in thermorecpeptors that transmit a signal to the brain. The brain tells more superficial vessels to dilate and lower vessels to constrict. We cool mainly by radiation.The opposite happens when we are cold. Vessels contract. (We turn blue) and then shiver if it keeps getting colder.11Cutaneous Sensation

Meissners Corpuscles: (light touch detection) egg shaped, in dermal papillae. Lots of them in fingertips, palms soles, eyelids, tongue, nipples, clitoris, tip of penisPacinian Corpuscle:: (pressure detection) onion shaped deep dermis and subcutaneous regions.Merkels Disk: 12Nerve FibersAssociated with muscles, glands and sensory receptors.

Vitamin D Synthesis

UV rays from the sun stimulate molecules in the skin that travel to the kidneys and liver to be converted to vitamin D.14Blood Reservoir

Structure of Epidermis

BOYS SAY GIRLS LOVE CHOCOLATE5- layers in palms and heels, but only 4 everywhere else. No Stratum lucidum. You must read and learn about the different layers. Basically, they are live cells at the bottom but die on their way to the top and become keratinized.Stratum basale: single row of mitosing cuboidal epithelial cells and melanocytes16KeritanizationProcess that converts basale skin cells into dead, flattened, hardened bags of keratin protein.http://www.youtube.com/watch?v=OKosGSm7Ps4Melanocytes

Specialized cells that produce the pigment melanin. Melanin absorbs UV rays and gives our flesh its color. Notice how the melanocyte has arms that reach up between the cells of the stratum spinosum.18EpidermisMain Job: ProtectionWaterproofingProtect lower layers from traumaBarrier against microorganisms and chemicalsDermisPapillary layer (20%)Loose areolar CTReticular layer (80%)Dense irregular CT

Dermis is where all the blood vessels and nerves are found. These layers supply nutrients to the epidermis layer called stratum basale.20Papillary Layer

Papillary layerReticular LayerSection 2 is the papillary layer of areolar loose CT. The curviness gives the boundary between epidermis and dermis more surface area. Thats a good thing, since that is the only source of nutrients to the epidermal layer. Reticular layer of dense irregular CT allows stretchiness in every direction making our skin resilient. 21Dermal Papilla = fingerprints

Projections from the papillary region are visible on our fingertips as a fingerprint. A similar pattern is seen on our heels. Dermal papillae contain nerve endings (Meissners Corpuscles) for touch and capillaries.22Reticular Layer

Pacinian CorpuscleMeissners CorpuscleHome of Pacinian corpuscles: sensory receptor for deep pressure. Reticular CT can stretch in many directions. It gives skin its strength and resiliency. Small tears in this layer are what make stretchmarks. Pacinian Corpuscles in this layer sense pressure.23Subcutaneous Layer(hypodermis)

Adipose TissueAndLoose CTMostly adipose tissue and blood vessels.24Accessory Organs I

Hair papillaHair is present all over except on the palms, soles, lips, nipples and external parts of some reproductive organs. Hair on forehead or inside of arm is not well-defined, but it is there. Hair follicle: tube-like depression in the epidermal layer.Hair papilla: connective tissue where hair cells divide. Blood vessels housed here. They are living cells at the bottom of the shaft, but die and become keratinized toward the skin surface. Hair is just dead epidermal cells.Arrector Pili Muscle: smooth muscle found with every hair follicle. It causes hair to stand on end when frightened or cold.25HairRoot vs. shaftGrowth influenced by nutrition and testosteroneAlopecia

Alopecia = thinning hair or loss of hair.26Accessory Organs II

Specialized Epithelial CellsNails grow from epithelial cells that divide and become keratinized. The nail plate overlies the nail bed. The nail bed is just specialized epithelial cells continuous with the skin. The lunula is the most active growing region.27Accessory Organs IIISkin glandsSebaceousSudoriferous (Sweat)MerocrineApocrine

Stinky and associated with hair folliclesSebaceous glands are holocrine (excrete the whole cell). They secrete a mixture of fat and dead cells called sebum that keep hair soft and waterproof.On your lips, they are not associated with a hair follicle.Sweat glands are merocrine glands. They secrete mostly water, but some salts and wastes through skin pores.Apocrine glands are the sweat glands in the armpits, the groin and around the nipples. They open into hair shafts, but are really just merocrine glands. The secretion of these glands begin to smell when they are eaten by skin bacteria.Ear wax comes from a specialized sweat gland, and so does breast milk.28Sudoriferous GlandsEccrine or Sweat Glands(Merocrine)

Most numerous overall. 2.5 million distributed over your body. Lots of them in the palms of hands, soles of feet and forehead.29Sudoriferous GlandsApocrine glands found in axillary regions

Also a merocrine type of gland, but the secretions are stinky when eaten by bacteria on the surface of your skin. Earwax, or cerumen, is secreted by a specialized sweat gland called a ceruminous gland.30Sebaceous (Oil) GlandsSecrete sebum oilBlackheads & Acne

Secretion stimulated by hormones. The oil helps waterproof our skin, keep hair moisturized. Also prevents bacterial growth on surface of skin.Blackheads = dead skin cells and sebum blocks the hair follicle. The condition can become Acne.31Accessory OrgansAll of these accessories are located in the dermis, but they are derived from embryonic epidermal cells!

Glands, skin, nails all develop from embryonic epidermis.32

Skin ColorMelanin production controlled by several genes.UV exposure darkens melanin and stimulates melanocytes to produce more pigment

We all have essentially the same number of melanocytes, but they produce different amounts of melanin determined by DNA.

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Darker or Lighter?Same # melanocytesMore melaninLarge, single pigment granules

Same # melanocytesLess melaninSmaller granules in groups of 2 to 4MelaninBrown or blackProtects deeper layers from UVFrecklesAlbinismVitiligo

Freckles are melanin in patches. Albinism is an inherited inability to produce melanin. Vitiligo is a partial loss of melanocytes from a small portion of the skin.35Other pigmentsCarotene in the dermisHemoglobin in capillaries

Skin Color CluesCyanosisJaundiceErythemaPallorBronzingBruises

ErythemaJaundiceCyanosisCyanosis is from low oxygen content. Jaundice is caused by a build up of bilirubin associated with liver dysfunction. Pallor is just going pale maybe from shock. Bronzing can be caused by a build up of too much iron. Erythema is redness caused by the immune system sending blood to the site of an injury or infection. Bronzing may be from a buildup of iron.37Healing WoundsShallow CutsIncreased production in stratum basale

Deeper CutsInflammationBlood clottingScabbingFibroblast infiltrationScab falls offIf shallow, epithelial cells along the margin divide more rapidly to bridge the gap.If Deeper:Inflammation occurs to kill microbesA clot of fibrous proteins (fibrin), blood cells and platelets forms. The clot forms a scab. Fibroblasts migrate to the region and form new collagen fibers that help close the wound. Growth factors in the matrix stimulate growth and repair.In large open wounds, granulations may develop during the healing process. They are clusters of newly formed blood vessels and fibroblasts that eventually turn into scar tissue.The scab falls off.38Wound Healing

InjuryBlood leaves vesselsClot forms Scab = dried blood and tissueFIBROBLASTS form new CTScab falls off

GRANULATIONTissue(vessel + fibroblasts)39Granulation Tissue

Healing burnsFirst degree (superficial partial-thickness)Epidermis onlyRedding from increased blood flowMild painHeals in a few days or weeks

2nd Degree Burns(Deep Partial-thickness)Epidermis and DermisRedness, BlistersModerate PainHeals in 2-6 weeks without scarsCommon kitchen burn423rd Degree BurnFull-thickness burnPossible subcutaneal damageProlonged heat or chemical contactRequires a graft

Autograft is from yourself. Homograft is from a cadaver. Skin substitutes are available. Major scarring and loss of ability to grow hair, sweat or feel.43Life-Span ChangesPatches of pigments (AGE SPOTS)Wound repair is slowerLess oilSlowed melanin production = gray hairLess Vitamin D synthesisShrinking vessels & glandsShrinking dermis & loss of fat = wrinkles & saggingFewer pain/pressure receptors

Skin CancerBasal Cell CarcinomaOriginates from basal cell keratinocytes Open sores, red patch, bump or scarOver 40, light skinCan be disfiguring but not life threatening

Skin CancerSquamous Cell CarcinomaLeast malignant & most commonKeratinocytes in stratum spinosum

http://www.mayoclinic.com/health/melanoma/MM0065746Skin CancerCutaneous melanomaCancer of melanocytesFair skinned people who get a few blistering sunburns

Dont forget your sunscreen.