1. 1 Chapter 6 The Integumentary System Skin and its accessory structures Skin and its accessory structures –structure –function –growth and repair –development –aging –disorders

2. 2 General Anatomy A large organ composed of all 4 tissue types A large organ composed of all 4 tissue types 22 square feet 22 square feet 1-2 mm thick 1-2 mm thick Weight 10 lbs. Weight 10 lbs.

3. 3Overview 2 Major layers of skin 2 Major layers of skin –epidermis is epithelial tissue only –dermis is layer of connective tissue, nerve & muscle Subcutaneous tissue (subQ or hypodermis) is layer of adipose & areolar tissue Subcutaneous tissue (subQ or hypodermis) is layer of adipose & areolar tissue –subQ = subcutaneous injection –intradermal = within the skin layer

4. 4 Overview of Epidermis Stratified squamous epithelium Stratified squamous epithelium Contains no blood vessels Contains no blood vessels 4 types of cells 4 types of cells 5 distinct strata (layers) of cells 5 distinct strata (layers) of cells

5. 5 Cell types of the Epidermis Keratinocytes--90% Keratinocytes--90% –produce keratin Melanocytes-----8 % Melanocytes-----8 % –produces melanin pigment –melanin transferred to other cells with long cell processes Langerhan cells Langerhan cells –from bone marrow –provide immunity Merkel cells Merkel cells –in deepest layer –form touch receptor with sensory neuron

6. 6 Layers (Strata) of the Epidermis Stratum corneum Stratum corneum Stratum lucidum Stratum lucidum Stratum granulosum Stratum granulosum Stratum spinosum Stratum spinosum Stratum basale Stratum basale

7. 7 Stratum Basale Deepest single layer of cells Deepest single layer of cells Called stratum germinativum Called stratum germinativum Combination of merkel cells, melanocytes, keratinocytes & stem cells that divide repeatedly Combination of merkel cells, melanocytes, keratinocytes & stem cells that divide repeatedly

8. 8 Stratum Spinosum 8 to 10 cell layers held together by desmosomes 8 to 10 cell layers held together by desmosomes During slide preparation, cells shrink and look spiny During slide preparation, cells shrink and look spiny Melanin taken in by phagocytosis from nearby melanocytes Melanin taken in by phagocytosis from nearby melanocytes

9. 9 Stratum Granulosum 3 - 5 layers of flat dying cells 3 - 5 layers of flat dying cells Show nuclear degeneration Show nuclear degeneration Contain dark-staining keratohyalin granules Contain dark-staining keratohyalin granules Contain lamellar granules that release lipid that repels water Contain lamellar granules that release lipid that repels water

10. 10 Stratum Lucidum Seen in thick skin on palms & soles of feet Seen in thick skin on palms & soles of feet Three to five layers of clear, flat, dead cells Three to five layers of clear, flat, dead cells Contains precursor of keratin Contains precursor of keratin

11. 11 Stratum Corneum 25 to 30 layers of flat dead cells filled with keratin and surrounded by lipids 25 to 30 layers of flat dead cells filled with keratin and surrounded by lipids Continuously shed Continuously shed Barrier to light, heat, water, chemicals & bacteria Barrier to light, heat, water, chemicals & bacteria Friction stimulates callus formation Friction stimulates callus formation

12. 12 Keratinization & Epidermal Growth Stem cells divide to produce keratinocytes Stem cells divide to produce keratinocytes As keratinocytes are pushed up towards the surface, they fill with keratin As keratinocytes are pushed up towards the surface, they fill with keratin 4 week journey unless outer layers removed in abrasion 4 week journey unless outer layers removed in abrasion Psoriasis = chronic skin disorder Psoriasis = chronic skin disorder –cells shed in 7 to 10 days as flaky silvery scales –abnormal keratin produced

13. 13 Skin Grafts New skin can not regenerate if stratum basale and its stem cells are destroyed New skin can not regenerate if stratum basale and its stem cells are destroyed Skin graft is covering of wound with piece of healthy skin Skin graft is covering of wound with piece of healthy skin –autograft from self –isograft from twin –autologous skin  transplantation of patients skin grown in culture

14. 14 Dermis Connective tissue layer composed of collagen & elastic fibers, fibroblasts, macrophages & fat cells Connective tissue layer composed of collagen & elastic fibers, fibroblasts, macrophages & fat cells Contains hair follicles, glands, nerves & blood vessels Contains hair follicles, glands, nerves & blood vessels Major regions of dermis Major regions of dermis –papillary region –reticular region

15. 15 Papillary Region Top 20% of dermis Top 20% of dermis Composed of loose CT & elastic fibers Composed of loose CT & elastic fibers Finger like projections called dermal papillae Finger like projections called dermal papillae Functions Functions –anchors epidermis to dermis –contains capillaries that feed epidermis –contains Meissner’s corpuscles (touch) & free nerve endings (pain and temperature)

16. 16 Reticular Region Reticular Region Dense irregular connective tissue Dense irregular connective tissue Contains interlacing collagen and elastic fibers Contains interlacing collagen and elastic fibers Packed with oil glands, sweat gland ducts, fat & hair follicles Packed with oil glands, sweat gland ducts, fat & hair follicles Provides strength, extensibility & elasticity to skin Provides strength, extensibility & elasticity to skin –stretch marks are dermal tears from extreme stretching Epidermal ridges form in fetus as epidermis conforms to dermal papillae Epidermal ridges form in fetus as epidermis conforms to dermal papillae –fingerprints are left by sweat glands open on ridges –increase grip of hand

17. 17 Skin Color Pigments (1) Melanin produced in epidermis by melanocytes Melanin produced in epidermis by melanocytes –same number of melanocytes in everyone, but differing amounts of pigment produced –results vary from yellow to tan to black color –melanocytes convert tyrosine to melanin  UV in sunlight increases melanin production Clinical observations Clinical observations –freckles or liver spots = melanocytes in a patch –albinism = inherited lack of tyrosinase; no pigment –vitiligo = autoimmune loss of melanocytes in areas of the skin produces white patches

18. 18 Skin Color Pigments (2) Carotene in dermis Carotene in dermis –yellow-orange pigment (precursor of vitamin A) –found in stratum corneum & dermis Hemoglobin Hemoglobin –red, oxygen-carrying pigment in blood cells –if other pigments are not present, epidermis is translucent so pinkness will be evident

19. 19 Skin Color as Diagnostic Clue Jaundice Jaundice –yellowish color to skin and whites of eyes –buildup of yellow bilirubin in blood from liver disease Cyanotic Cyanotic –bluish color to nail beds and skin –hemoglobin depleted of oxygen looks purple-blue Erythema Erythema –redness of skin due to enlargement of capillaries in dermis – during inflammation, infection, allergy or burns

20. 20 Accessory Structures of Skin Epidermal derivatives Epidermal derivatives Cells sink inward during development to form: Cells sink inward during development to form: –hair –oil glands –sweat glands –nails

21. 21 Structure of Hair Structure of Hair Shaft -- visible Shaft -- visible –medulla, cortex & cuticle –CS round in straight hair –CS oval in wavy hair Root -- below the surface Root -- below the surface Follicle surrounds root Follicle surrounds root –external root sheath –internal root sheath –base of follicle is bulb  blood vessels  germinal cell layer

22. 22 Hair Related Structures A rrector pili A rrector pili –smooth muscle in dermis contracts with cold or fear. –forms goosebumps as hair is pulled vertically Hair root plexus Hair root plexus –detect hair movement

23. 23 Hair Growth Growth cycle = growth stage & resting stage Growth cycle = growth stage & resting stage Growth stage Growth stage – lasts for 2 to 6 years – matrix cells at base of hair root producing length Resting stage Resting stage – lasts for 3 months –matrix cells inactive & follicle atrophies Old hair falls out as growth stage begins again Old hair falls out as growth stage begins again –normal hair loss is 70 to 100 hairs per day

24. 24 Hair Color Result of melanin produced in melanocytes in hair bulb Result of melanin produced in melanocytes in hair bulb Dark hair contains true melanin Dark hair contains true melanin Blond and red hair contain melanin with iron and sulfur added Blond and red hair contain melanin with iron and sulfur added Graying hair is result of decline in melanin production Graying hair is result of decline in melanin production White hair has air bubbles in the medullary shaft White hair has air bubbles in the medullary shaft

25. 25 Functions of Hair Functions of Hair P revents heat loss P revents heat loss Decreases sunburn Decreases sunburn Eyelashes help protect eyes Eyelashes help protect eyes Touch receptors (hair root plexus) senses light touch Touch receptors (hair root plexus) senses light touch

26. 26 Glands of the Skin Specialized exocrine glands found in dermis Specialized exocrine glands found in dermis Sebaceous (oil) glands Sebaceous (oil) glands Sudiferous (sweat) glands Sudiferous (sweat) glands Ceruminous (wax) glands Ceruminous (wax) glands Mammary (milk) glands Mammary (milk) glands

27. 27 Sebaceous (oil) glands Secretory portion in the dermis Secretory portion in the dermis Most open onto hair shafts Most open onto hair shafts Sebum Sebum –combination of cholesterol, proteins, fats & salts –keeps hair and skin from soft & pliable –inhibits growth of bacteria & fungi(ringworm) Acne Acne –bacterial inflammation of glands –secretions stimulated by hormones at puberty

28. 28 Sudoriferous (sweat) glands Sudoriferous (sweat) glands Eccrine (sweat) glands Eccrine (sweat) glands –most areas of skin –secretory portion in dermis with duct to surface –regulate body temperature with perspiration Apocrine (sweat) glands Apocrine (sweat) glands –armpit and pubic region –secretory portion in dermis with duct that opens onto hair follicle –secretions more viscous

29. 29 Ceruminous glands Ceruminous glands Modified sweat glands produce waxy secretion in ear canal Modified sweat glands produce waxy secretion in ear canal Cerumin contains secretions of oil and wax glands Cerumin contains secretions of oil and wax glands Helps form barrier for entrance of foreign bodies Helps form barrier for entrance of foreign bodies Impacted cerumen may reduce hearing Impacted cerumen may reduce hearing

30. 30 Nails Nails Tightly packed, keratinized cells Tightly packed, keratinized cells Nail body is pink due to underlying capillaries Nail body is pink due to underlying capillaries Lunula appears white due to thickened stratum basale in that area Lunula appears white due to thickened stratum basale in that area Cuticle (eponychium) is stratum corneum Cuticle (eponychium) is stratum corneum Nail matrix deep to the nail root is the region from which the nail growth occurs Nail matrix deep to the nail root is the region from which the nail growth occurs Growth is 1mm per week--faster in summer & on most-used hand Growth is 1mm per week--faster in summer & on most-used hand

31. 31 Structure of Nails Tightly packed keratinized cells Tightly packed keratinized cells Nail body Nail body –visible portion pink due to underlying capillaries –free edge appears white Nail root Nail root –buried under skin layers –lunula is white due to thickened stratum basale Eponychium (cuticle) Eponychium (cuticle) –stratum corneum layer

32. 32 Nail Growth Nail matrix below nail root produces growth Nail matrix below nail root produces growth Cells transformed into tightly packed keratinized cells Cells transformed into tightly packed keratinized cells 1 mm per week 1 mm per week

33. 33 Types of Skin Thin skin Thin skin –covers most of body –thin epidermis (.1 to.15 mm.) that lacks stratum lucidum –lacks epidermal ridges, has fewer sweat glands and sensory receptors Thick skin Thick skin –only on palms and soles –thick epidermis (.6 to 4.5 mm.) with distinct stratum lucidum & thick stratum corneum –lacks hair follicles and sebaceous glands

34. 34 General Functions of the Skin Regulation of body temperature Regulation of body temperature Protection as physical barrier Protection as physical barrier Sensory receptors Sensory receptors Excretion and absorption Excretion and absorption Synthesis of vitamin Synthesis of vitamin

35. 35 Thermoregulation Releasing of sweat onto the skin Releasing of sweat onto the skin –perspiration & its evaporation lowers body temperature Adjusting flow of blood to the body surface Adjusting flow of blood to the body surface –in moderate exercise, more blood brought to surface helps lower temperature –with extreme exercise, blood is shunted to muscles and body temperature rises Shivering and constriction of surface vessels Shivering and constriction of surface vessels –raise internal body temperature as needed

36. 36 Protection Physical, chemical and biological barrier Physical, chemical and biological barrier –tight cell junctions prevent bacterial invasion –lipids released retard evaporation –pigment protects somewhat against UV light –langerhans cells alert immune system

37. 37 Cutaneous Sensations Touch, temperature, pressure, vibration, tickling and some pain sensations arise from the skin. Touch, temperature, pressure, vibration, tickling and some pain sensations arise from the skin.

38. 38 Excretion and Absorption Only a minor role is played by the skin Only a minor role is played by the skin 400 mL of water evaporates from it daily 400 mL of water evaporates from it daily Small amounts salt, CO2, ammonia and urea are excreted Small amounts salt, CO2, ammonia and urea are excreted Lipid soluble substances can be absorbed through the skin Lipid soluble substances can be absorbed through the skin –vitamins A, D, E and K, Oxygen and CO2 –acetone and dry-cleaning fluid, lead, mercury, arsenic, poisons in poison ivy and oak

39. 39 Transdermal Drug Administration Method by which drugs in a patch enter the body Method by which drugs in a patch enter the body Drug absorption most rapid in areas where skin is thin (scrotum, face and scalp) Drug absorption most rapid in areas where skin is thin (scrotum, face and scalp) Examples Examples –nitroglycerin (prevention of chest pain from coronary artery disease) –scopolamine ( motion sickness) –estradiol (estrogen replacement therapy) –nicotine (stop smoking alternative)

40. 40 Synthesis of Vitamin D Sunlight activates a precursor to vitamin D Sunlight activates a precursor to vitamin D Enzymes in the liver and kidneys transform that molecule into calcitriol (most active form of vitamin D) Enzymes in the liver and kidneys transform that molecule into calcitriol (most active form of vitamin D) Necessary vitamin for absorption of calcium from food in the gastrointestinal tract Necessary vitamin for absorption of calcium from food in the gastrointestinal tract

41. 41 Epidermal Wound Healing Abrasion or minor burn Abrasion or minor burn Basal cells migrate across the wound Basal cells migrate across the wound Contact inhibition with other cells stops migration Contact inhibition with other cells stops migration Epidermal growth factor stimulates cell division Epidermal growth factor stimulates cell division Full thickness of epidermis results from further cell division Full thickness of epidermis results from further cell division

42. 42 Deep Wound Healing Deep Wound Healing If an injury reaches dermis, healing occurs in 4 phases If an injury reaches dermis, healing occurs in 4 phases –inflammatory phase has clot unite wound edges and WBCs arrive from dilated and more permeable blood vessels –migratory phase begins the regrowth of epithelial cells and the formation of scar tissue by the fibroblasts –proliferative phase is a completion of tissue formation –maturation phase sees the scab fall off Scar formation Scar formation –hypertrophic scar remains within the boundaries of the original wound –keloid scar extends into previously normal tissue  collagen fibers are very dense and fewer blood vessels are present so the tissue is lighter in color

43. 43 Phases of Deep Wound Healing Which phases have been left out of this illustration?

44. 44 Age Related Structural Changes Collagen fibers decrease in number & stiffen Collagen fibers decrease in number & stiffen Elastic fibers become less elastic Elastic fibers become less elastic Fibroblasts decrease in number Fibroblasts decrease in number Langerhans cells and macrophages decrease in number and become less-efficient phagocytes Langerhans cells and macrophages decrease in number and become less-efficient phagocytes Oil glands shrink and the skin becomes dry Oil glands shrink and the skin becomes dry Walls of blood vessels in dermis thicken so decreased nutrient availability leads to thinner skin as subcutaneous fat is lost Walls of blood vessels in dermis thicken so decreased nutrient availability leads to thinner skin as subcutaneous fat is lost

45. 45 Photodamage Ultraviolet light (UVA and UVB) both damage the skin Ultraviolet light (UVA and UVB) both damage the skin Acute overexposure causes sunburn Acute overexposure causes sunburn DNA damage in epidermal cells can lead to skin cancer DNA damage in epidermal cells can lead to skin cancer UVA produces oxygen free radicals that damage collagen and elastic fibers and lead to wrinkling of the skin UVA produces oxygen free radicals that damage collagen and elastic fibers and lead to wrinkling of the skin

46. 46 Skin Cancer 1 million cases diagnosed per year 1 million cases diagnosed per year 3 common forms of skin cancer 3 common forms of skin cancer –basal cell carcinoma (rarely metastasize) –squamous cell carcinoma (may metastasize) –malignant melanomas (metastasize rapidly)  most common cancer in young women  arise from melanocytes ----life threatening  key to treatment is early detection watch for changes in symmetry, border, color and size  risks factors include-- skin color, sun exposure, family history, age and immunological status

47. 47 Burns Destruction of proteins of the skin Destruction of proteins of the skin –chemicals, electricity, heat Problems that result Problems that result –shock due to water, plasma and plasma protein loss –circulatory & kidney problems from loss of plasma –bacterial infection

48. 48 Types of Burns First-degree First-degree –only epidermis (sunburn) Second-degree burn Second-degree burn –destroys entire epidermis & part of dermis –fluid-filled blisters separate epidermis & dermis –epidermal derivatives are not damaged –heals without grafting in 3 to 4 weeks & may scar Third-degree or full-thickness Third-degree or full-thickness –destroy epidermis, dermis & epidermal derivatives –damaged area is numb due to loss of sensory nerves

49. 49 Pressure Sores Decubitus ulcers Decubitus ulcers Caused by constant deficiency of blood flow to tissue Caused by constant deficiency of blood flow to tissue Areas affected is skin over bony prominence in bedridden patients Areas affected is skin over bony prominence in bedridden patients Preventable with proper care Preventable with proper care