Learning Objectives1.) Name the layers of the epidermis.2.) Name appendages within the dermis.3.) List the major functions of the skin.4.) Name components of the pilosebaceous unit.5.) Name the three stages of hair growth.
Integumentary systemThe skin and its accessory organs Sebaceous glands Sudoriferous glands Sensory perceptors Hair Nails
Pilosebaceous unitThe hair follicle and its appendages Internal and external root sheaths Hair shaft Dermal papilla Sebaceous gland Arrector pili muscle
Overall Look at SkinBody’s largest organ Up to 20 square feet on the average personMade of epithelial tissue and connective tissue Epithelial – forms thin protective layer Connective – binds, protects, cushions, & supports3 main layers Epidermis Dermis Subcutis or subcutaneous layer
Epidermis “Horny Zone” Cells divide in the lowestStratum Corneum layer Migrate up to replace deadStratum Lucidum cells that have been shedStratum Granulosum As they move up, they are “Germinal Zone” filled with keratin to protectStratum Spinosum against invasion (keratinization)Stratum Germinativum
Stratum CorneumA.K.A – “horny layer”Outermost layer of dead skin cellsConstantly sheddingMostly bound by sebum Sebum – fatty or oily secretion of sebaceous gland; serves as lubrication
Stratum LucidumBelow stratum corneumCells allow light to pass through themOnly present in palms of hands and soles of feet, where epidermis is thickestPurpose unknown
Stratum GranulosumAKA – “granular layer”Cells are livingAs cells are pushed upward, lose nuclei and dieGives skin opaque appearanceVaries in thickness Persistent friction and pressure cause areas to thicken for protection and form calluses
Stratum SpinosumAKA – “Prickle cell layer”Made of living cellsAttached to each other by prickly shaped fibers
Stratum GerminativumLowest layer of epidermisMitosis (cell division) occurs hereCells migrate up, replacing dead skin cells that have been shedDesquamation (exfoliating dead skin cells) takes about 28 daysStratum mucosum – single cell layer
Stratum GerminativumContains melanocytes UV rays react with amino acid tyrosine found in melanocytes to produce melaninMelanin Dark pigment gives skin color and protects dermis from UV radiation and sun damage
Skin ColorSkin color depends on melaninPeople have same number of melanocytes Dark skin – melanocytes are more active, producing more melanin
DermisLiving layer or “true skin”Made of dense connective tissueDivided into two layers Papillary layer Reticular layer
Papillary layerMade of fibers called papillae Connects epidermis and dermisSuperficial capillaries looped around papillaeNerve endings sensitive to touchThis layer forms the connective tissue sheath around hair follicles.
Reticular LayerThickest layer of skinDense bundles of collagen fibers Fibers are denser closer to papillary layer and thin as they near the fatty subcutaneous tissueAppendages Arrector pili muscles Blood vessels Fat cells Hair follicles Lymph vessels Nerve endings Sebaceous glands Sudoriferous glands
Blood SupplyArteries and veins circulate into the dermis and branch into smaller capillaries at the hair follicles, the hair papillae, and glandsTransports oxygen-rich blood and nutrients essential for: Growth Reproduction Tissue repair
Lymph SupplyLymph glands produce lymph Contains waste products, salts, nitrogenous wastes Carried through vessels to lymph nodes and fluid is filtered for excretion
Sudoriferous GlandsSweat glandsFound deep in dermis Tubular ducts going to pores in epidermisTwo kinds of sweat glands: Apocrine Eccrine
Types of Sudoriferous GlandsApocrine Found in genital area and armpits (axillae) Create body odor Believed to excrete pheromonesEccrine Found all over body Increased numbers on forehead, palms, soles of feet
Sebaceous GlandsFound all over skinMost often appendages to the hair follicles and open into the shafts of the folliclesProduce waxy, oily substance called sebum which lubricates skin Most active during puberty
Nerve EndingsCarry impulses to the brainFound at various levels, various shapes, depending on purposeMost superficial are responsible for touchClose to surface is pain receptor Below that are receptors for heat and coldDeeper in dermis are pressure receptors
Hair AKA – pilosebaceous unit Found all over body except palms of hands and soles of feet Most is invisible to naked eyeDenser on head and limbs, after puberty in groin area and axillae (armpits) Hair growth influenced by hormones and genetic inheritance
Subcutaneous LayerLocated at base of dermisLayer of fatty tissueAKA – subcutis; adipose tissueSeparates dermis from muscles and helps skin to move over themContains arteries, veins, lymph, nerve endings, fat cells
Structure of Hair – Follicular Canal and SheathsFollicular canal – depression in the skin that houses the hairExternal root sheath – inner side of canal
Hair ShaftLined with epidermal tissue extends through dermis into subcutaneous tissueEpidermal cells produce follicle and hair matrixBase of follicle widens into hair follicle bulb Bulb – where hair grows; contains hair matrix which is where cell division occurs Hair matrix produces the hair and external and internal root sheath
Internal Root SheathInnermost layer of the follicleCan sometimes see on tweezed hair Looks like clump of petroleum jellyProtects hair up as far as sebaceous gland
Dermal Papilla and PapillaeDermal papilla – located at base of bulb Layer of dermal tissue that attaches itself to the epidermis with papillaePapillae contain blood vessels – needed for nutrients and hormones for growth
Arrector Pili MuscleAttaches to the underside of the hair at the dermal papilla and the hair shaftResponsible for lifting the hair, trapping a layer of air on the skin’s surface assisting in heat regulation fear and cold stimulate contraction causes “goose bumps”
Sebaceous GlandAttached to hair follicle and opens into shaftSecretes sebum Lubricates hair to prevent dryness and breakage Lubricates epidermis to prevent dryness and to prevent bacteria and germs from entering
Layers of the Hair3 layers compose the hair: 1.) Cuticle 2.) Cortex 3.) Medulla
CuticleOutermost layerPurpose: protect inner layers of the hair
CortexBelow the cuticleContains pigment that gives hair its colorGives hair its strength and elasticity
MedullaInnermost layerAKA – pith or marrowFine hair lacks medullaCan be found in all wavy hair General rule: curlier the hair, the stronger the medulla
3 Types of Hair1.) Lanugo2.) Vellus3.) Terminal
LanugoAKA – fetal hairSoft, downy hair on fetuses in utero and infants at birth, covering bodies and scalpMay contain pigment, light or darkSheds a few weeks after birthPermanent hair begins to grow in
Vellus – “peach fuzz”Confused with lanugo; difference is vellus is present through adulthoodFine, short, often no pigment or medullaWomen believed to have 55% more vellus hair than men
TerminalLonger, coarser hair that covers scalp, arms, legs, groin area, axillae, and on faces, chests, and backs of menHair follicles can produce vellus or terminal hair.Affected by: Age Genetics Health Hormonal changes of puberty, pregnancy, and menopause
Anagen: The Growing PhaseHair follicle at its deepestHair matrix active, surrounding the dermal papillaCan be affected by health of the individualOnce hair reaches full length it can remain there, depending on location, for varying amounts of time.
Catagen: The Transitional PhaseFollicle separates from dermal papilla and shrinks to 1/3 of sizeThin cord of epidermal tissue attaching follicle to dermal papilla retracts upward with the dermal papillaShortest hair growth stage
Telogen: The Resting StageFollicle is 1/3 of original sizeBase looks like clubBulb is usually whiteDermal papilla is separated from hair follicle and attached by thin cord of epidermal cells; will be released by end of phase
Hair GrowthIncomplete scienceThings we know: Hair grows faster in the summer Good health improve hair growth Young people experience more hair growth Increase in number of telogen hairs during illness, after childbirth, and when experiencing stress.
Functions of the SkinLargest sensory organMultiple functions: Protection Heat regulation Excretion – discharging waste material Secretion – producing and discharging substances from glands Absorption – uptake of one substance into another Sensation Synthesis of Vitamin DHair plays important role in these functions.
ProtectionSkin protects the body against the environment and invasion of bacteria.Skin is usually NOT sterile and is covered by bacteria Noninvading and nonpathogenic bacteriaBuilt-in protective aid, ACID MANTLE
Acid MantlepH of 5 to 5.6Created by the combined activity of sweat and sebaceous glands Perspiration is acidic and acts as bactericide (inhibits growth of bacteria) NOT TRUE of areas of higher perspiration (groin and axillae), skin is softer and less acidity in excessive perspiration
Protection continuedWhen organism does invade skin, reactions (inflammation, swelling, welts) occur.Leucocytes are released and destroy the invading organism.Reactions help to prevent spread of infection to surrounding tissue.
Protection continuedHorny layer acts as barrierSkin is waterproof (thanks in part to sebum)Sebum prevents drying and cracking → prevents bacteria and germs from enteringWhen intact, skin prevents harmful fluids from entering and prevents water, blood, and lymph from leaving.
Protection continuedStratum germinativum protects by containing melanocytes which produce melanin Melanin – the body’s own sunscreen which protects from harmful UV radiationDark skin get better protection, few incidences of skin cancer
Protection continuedAdipose tissue – cushions the body from falls, protects against minor trauma, and provides source of energy
Protection by Lymphatic SystemLymphatic fluid and lymphocytes are produced in lymph nodes. Lymphocytes transported through lymph vessels Engulf bacteria Carried back to lymph nodes Filtered and drained of waste products
Heat RegulationHealthy body temperature of 98°F or 37°CSkin helps body to adjust and maintain a safe temperature Evaporation Perspiration Radiation Insulation
Heat Regulation - RadiationRadiation from constriction or dilation of capillaries affect body temperature. Dilation (expansion) causes surface heat of body to be reduced through radiation. Causes flushed appearance. Constriction (contraction) slows blood flow, preserving heat. Gives skin bluish tint.
Heat Regulation - InsulationArrector pili muscle contracts, lifts hair, trapping a layer of insulating air on skin’s surface. (Air is the best insulator!)Sebum lubricates hair, preventing it from breaking; allows hair to do its job.Adipose tissue acts as effective insulator, keeping body warm.
Secretion and ExcretionSebaceous glands – secrete sebum, skin’s natural lubricantSudoriferous glands – excrete salt, urea, and other waste material during perspiration.
SensationExperience heat, cold, pain, pressureDamage to nerves can leave the skin numb, once tissue has healed.
Absorption and PenetrationSkin can absorb oil- and fat-based substancesPharmaceutical creams and lotions penetrate the dermis and absorb into the blood supply Require medical guidance and physicians’ prescriptions to be obtained
Absorption and PenetrationCosmoceuticals contain NO drugs or medications but could cause drug reactions. May have deeper absorption qualities than over-the-counter cosmetics. Obtained from and require professional guidance of dermatologist, plastic surgeon, or skin-care professional.
1.) What are the three main layers of theskin?Epidermis, dermis, and subcutis or subcutaneous layer.
2.) Into which two zones is the epidermisdivided?Horny zone and germinal zone.
3.) Name two layers of the epidermis.Stratum corneum,stratum lucidum,stratum granulosum,stratum spinosum,stratum germinativum.
4.) In which layer are melanocytes found?Stratum germinativum
5.) What are the two layers of the dermis?Papillary layer and reticular layer
6.) What is a sudorific gland?A sweat gland, or gland that excretes salt, urea, and other waste material.
8.) Where is the hair matrix?In the hair follicle bulb
9.) What are the three stages of hairgrowth?Anagen, catagen, and telogen
10.) Name at least five functions of theskin.Protection, heat regulation, excretion, secretion, absorption, sensation, synthesis of Vitamin D.