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I. INTEGUMENTARY SYSTEM Components: Integument

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I. INTEGUMENTARY SYSTEM Components: Integument LECTURE OUTLINE & REVIEW QUESTIONS: INTEGUMENTARY SYSTEM ANATOMY 25 - GUTHRIE I. INTEGUMENTARY SYSTEM Stem cells > mitosis > new keratinocytes Components: Stratum spinosum Integument: outer covering of body Production of keratin filaments Appendages: hairs, nails, glands Progressive flattening of cells Increasing surface area II. INTEGUMENT Cells held together by desmosomes Components, superficial to deep: Stratum granulosum Epidermis } = “Skin” } Keratin filaments + keratohyaline granules > Dermis } } Integument keratin Hypodermis: } Lamellated granules: glycolipids > extracellular subcutaneous tissue or superficial fascia space Areolar c.t. Cell death Deep fascia Stratum corneum Dead, flattened cells packed with keratin Skin averages about: Desquamation 16% of body weight 2 square meters surface area Thin Skin vs. Thick Skin 2 mm thickness Refers to epidermal thickness Thin skin: A. EPIDERMIS Most of body Stratified squamous keratinized epithelium ~ 0.07-0.12mm thick (varies) Keratin = “soft” form Hairs 1. Cell Types: Thick skin: a. Keratinocytes Palms and soles Life Cycle: 0.4-0.6mm thick Mitosis of stem cells in basal layers glabrous (no hairs) Pushed toward surface by newer cells Keratin production & accumulation Thick skin: Progressive flattening All strata thicker. Lose nucleus and organelles May have an additional layer: Desquamate (~ 1 gram/day) Stratum lucidum Average Time: 28-30 days Between granulosum and corneum Functional Layers of Epidermis, Thin skin: (deep to superficial): All strata thinner Stratum basale (germinativum) No stratum lucidum A25lectout.inegument.mguthrie 1 LECTURE OUTLINE & REVIEW QUESTIONS: INTEGUMENTARY SYSTEM ANATOMY 25 - GUTHRIE Melanocyte processes contact keratinocytes Epidermal functions: surrounding it. Stratum corneum Produce and release melanin (pigment) Keratinized cells protect against: Tyrosine >>> melanin > melanosomes > physical and chemical trauma keratinocytes bacterial and parasitic invasion dehydration and imbibition Types of melanin: Eumelanin: brownish pigment, ovoid Stratum granulosum melanosomes Final keratin processing Pheomelanin: red-orange pigment, round Glycolipid coating of keratinocytes melanosomes Initial steps in Vitamin D production Melanocytes often “clearer” than surrounding Stratum spinosum keratinocytes Keratin precursors Increase in cell surface area Melanin function: Cell-to-cell adhesion: desmosomes Protects DNA from potentially mutagenic UV radiation (especially 290-320nm wavelengths) Stratum basale Stem cell divisions Tanning reactions: Initial: Some common epidermal phenomena Increased release of existing melanosomes Calluses & corns from melanocytes Blisters Melanosomes darken; cluster between Mucocutaneous junctions nucleus and incoming radiation. Response is ephemeral. b. Langerhans Cells Subsequent Exposures: Dendritic or APC cells Increased melanosome production and Part of mononuclear phagocyte system (MPS) release. Phagocytize and present antigens Tan loss: Initial: reversal of darkening, clustering c. Melanocytes Secondary: lysosomal destruction of Located mostly at dermal-epidermal junction, melanosomes; desquamation of cells lower layers of epidermis Form melanocyte-keratinocyte units: A25lectout.inegument.mguthrie 2 LECTURE OUTLINE & REVIEW QUESTIONS: INTEGUMENTARY SYSTEM ANATOMY 25 - GUTHRIE Skin color (pigmentation): Inability of melanocytes to take up tyrosine or Three additive components: defective tyrosinase. Melanin Melanocyte ger tyrosinase golgi body Carotenoids: yellowish pigment in tissues melanosome: tyrosine uptake; tyrosinase Hemoglobin: reddish pigment in blood catalyzes conversion of tyrosine to DOPA (1,3,4 Population and individual variations: dihydroxyphenalanine); DOPA Darker complexions: dopaquinone melanin Melanocytes more active > more melanosomes Melanomas Melanosomes: larger, tend remain unclustered in cell d. Merkel’s Cells persist through more layers of epidermis Tactile (touch) receptors Lighter complexions: Processes between surrounding keratinocytes Melanocytes less active > fewer Cell in contact with sensory nerve ending melanosomes Melanosomes: B. DERMIS smaller, tend cluster in cell Between epidermis and hypodermis restricted to lower layers of epidermis Two layers: Superficial: papillary layer. Loose (areolar) ct Some phenomena due to melanocytes: Projections (“papillae”) interlock with undersurface of Freckles epidermis Moles Deep: reticular layer. Dense irregular ct Pregnancy: Abundant collagenous & elastic fibers Cloasma: increased melanin in cheeks, Arranged to withstand mechanical stresses forehead Directions vary with body region Linea nigra: increased melanin over linea alba Cleavage planes in abdomen Areola: increased melanin Contents: “Mongoloid spot” Hair follicles & Arrectores pilorum mm. Bluish area of skin, usually in sacral region Sebaceous glands More common in Asian infants Sweat glands Melanin in deep dermis Eccrine Usually disappears with age Apocrine (axilla & perineum only) Albinism Sensory receptors Melanin absence Nerves: Genetic: autosomal recessive A25lectout.inegument.mguthrie 3 LECTURE OUTLINE & REVIEW QUESTIONS: INTEGUMENTARY SYSTEM ANATOMY 25 - GUTHRIE Autonomic > smooth m., glands Vascular Supply: Somatic > sensory receptors Arteries: Blood vessels Rete cutaneum: dermis-hypodermis junction Rete subpapillare: reticular-papillary junction Dermal – Epidermal interlocking Capillary loops into dermal papillae Thick skin: Veins: Basic pattern: Rete cutaneum: dermis-hypodermis junction Dermal ridge projects into undersurface of Rete subpapillare: reticular-papillary junction epidermis Plexus in middle of reticular layer Epidermal ridge projects into primary groove A-V Shunts: Direct artery-vein connections running length of dermal ridge. Thermoregulation: Papillae project from dermal ridge into epidermis Cold temperature exposure: A-V shunts dilate > Epidermal ridges project into furrows between less blood to outer skin capillaries > minimizes dermal ridges heat loss Sweat glands open into primary groove Hot temperature exposure: A-V shunts constrict > Functions: more blood to outer skin capillaries > maximizes Mechanical support heat loss Blood supply Blushing, flushing, and blanching Dermatoglyphs Palmar and plantar surfaces C. HYPODERMIS Surface grooves and ridges; reflect interlocking Aka: superficial fascia, subcutaneous tissue pattern Finger prints Superficial layer: Loops, whorls, arches White fat Palm prints, foot prints, toe prints Paniculus adiposus Genetics + environmental factors Lobulated or loculated Function: Increased friction Amount varies with age, sex, diet, health Functions: Flexion creases and expansion folds Insulation Cushioning Thin Skin: Lipid storage Interlocking less complex and extensive: Body contours “Peg” and “Socket” Secondary sexual characteristics Regional surface patterns A25lectout.inegument.mguthrie 4 LECTURE OUTLINE & REVIEW QUESTIONS: INTEGUMENTARY SYSTEM ANATOMY 25 - GUTHRIE Brown fat (adults) Follicle Structure & Terminology: Small amounts in limited areas Layers (external to internal) Dermal or connective tissue sheath III. APPENDAGES Glassy membrane Hairs, nails, glands External root sheath} essentially stratum basale. All are epidermal derivatives Internal root sheath } spinosum, granulosum Cuticle of the follicle (lower part of follicle only) A. HAIRS Bulb (bottom of follicle) Types: Hair matrix Coarse (terminal): scalp, axilla, pubic Small “hill” of epidermal cells Vellus (fine): most of body Mitosis of cells generates hair Lanugo (woolly): fetus Dermal papilla Hair Follicle Dermal connective tissue Downgrowth of epidermis into dermis Invaginates bottom of hair bulb Stratum corneum disappears Capillaries: vascular supply to matrix cells Follicle associated structures: Hair bulge Arrectores pilorum muscles (sing. = arrector pili) Located in upper follicle wall, near sebaceous Bands of smooth muscle gland duct Angle from follicle wall up to skin Cluster of stem cells Attachments: Migrate to hair matrix Lower end: ct of upper part of follicle Initiate hair growth Upper end: dermis just below epidermis Genetic control: nFAT gene ? Functions: Hair Structure & Terminology Hair follicles set at an angle to skin surface Essentially composed of concentric cylinders of dead Contraction of arrectores pilorum muscles keratinized cells produced by hair matrix cells. Decreases follicle angle (hairs “stand up”) Cuticle Pull surrounding skin down (“goose bumps”) Outermost cylinder of overlapping cells Occurs in response to cold, fear, excitement “Hard” keratin Thermoregulation: Cortex Traps insulating layer of air next to skin Inside cuticle Protection against assault: Thickness varies Animal looks “bigger” and “tougher” “Hard” keratin Harder to get a good “bite” Medulla (most coarse hairs) Sebaceous glands Inside cortex Located in angle between follicle and arrector pili “Soft” keratin Ducts open into follicle A25lectout.inegument.mguthrie 5 LECTURE OUTLINE & REVIEW QUESTIONS: INTEGUMENTARY SYSTEM ANATOMY 25 - GUTHRIE Hair root & shaft Eponychium (cuticle) = fold of epidermis at proximal Root anchored to follicle walls end of plate. Shaft free of follicle walls, exits at skin surface Hyponychium = attachment of undersurface of plate Hair growth cycles to epidermis of digit; just proximal to “free” or distal Active follicle end of the plate Hair bulge stem cells > matrix Lunula (“little moon”) = whitish area of plate just Dermal papilla invades matrix distal to eponychium Matrix cells divide mitotically to produce hair Most noticeable on pollex Hair
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