Chapter 5

1. Chapter 5 The Integumentary System (IS) Integument covering Covers the outside of the body & is easily observed Can be used as a diagnostic tool for determining health AP1 Chapter 5

2. Chapter 5 Outline • Overview of the Integumentary System • Skin • Hypodermis • Accessory Skin Structures • Summary of Integumentary System Functions • Effects of aging on the Integumentary System AP1 Chapter 5

3. I. Overview of the IS AP1 Chapter 5

4. I. Overview of the ISMajor Functions of the IS • Protection • Protects from abrasion & UV light • Prevents entry of microorganisms • Prevents water loss & thus dehydration • Sensation • Contains sensory receptors that detect temp, touch, pressure, & pain • Temperature Regulation • Regulated via blood flow thru skin & activity of sweat glands • Vitamin D Production • When exposed to UV can produce molecules that may be converted into Vit D • Excretion • Small amounts of wastes are excreted thru gland secretions AP1 Chapter 5

5. II. Skin Epidermis Thick & Thin Skin Skin Color Dermis AP1 Chapter 5

6. II. Skin Epidermis Dermis Epidermis sits on top of dermis CT Responsible for most of the structural strength of the skin • Most superficial & made up of epithelial tissue • Resists abrasion on skin surface • Reduces water loss thru skin Figure 5.1 Pg 150 AP1 Chapter 5

7. II. Skin: Epidermis • Strat. Squ. Epi separated from the dermis by a basement membrane • Not very thick & contains no blood vessels relying on diffusion for nourishment Figure 5.2 Pg 152 AP1 Chapter 5

8. II. Skin: Epidermis Cells that make-up the epidermis Dead Keratinocytes • Keratinocytes • Most of the cells of the epi belong is this category b/c they prod a protein mixture called keratin wh/ makes cells hard • This is the reason cells resist abrasion & reduce water loss • Melanocytes • Contribute to skin color • Langerhans Cells • Part of the immune system • Merkel Cells • Specialized cells associated with nerve endings responsible for detecting light touch & superficial pressure Keratinocytes Langerhans Cells Melanocytes Merkel cells AP1 Chapter 5

9. II. Skin: Epidermis • Cells of the epidermis are prod’d by mitosis in the deepest epi layer, as new cells are formed they push older cells toward the surface where they slough off (Desquamate). The outermost cells protect the deeper cells • Keratinization • Cells D shape & internal chemical composition becoming filled w/keratin • These cells eventually die & prod the outer layer of dead-hard cells that resist abrasion & forms a permeability layer AP1 Chapter 5

10. II. Skin: Epidermis • 5 layers of the epidermis Figure 5.3 pg 153 • Stratum Basale/Stratum Germinativum • Stratum Spinosum • Stratum Granulosum • Stratum Lucidum • Stratum Corneum AP1 Chapter 5

11. II. Skin: Epidermis5 layers • Stratum Basale • Structure • Deepest layer of the epi • Single layer of cube to columnar shaped cells • Basement membrane attaches the SB to the dermis • Function • Prod’n of cells of the most superficial layers • Melanocytes produce & contribute to melanin in cells wh/ protects against UV Figure 5.3 pg 153 • Hemidesmosomes hold SB to basement membrane • Desmosomes hold cells together • Keratinocytes undergo division every 19 days • 1 daughter pushes toward the surface while the other stays in the SB • 40-56 days from start in SB to slough off

12. II. Skin: Epidermis5 layers • Stratum Spinosum • Structure: • 8-10 layers of many sided cells that flatten as the are pushed toward the surface • Desmosomes are broken & reformed • If cells are pulled apart they take on a spikey appearance thus the name • There are additional keratin fibers & lipid filled organelles (Lamellar granules) • Fxn: • Production of keratin fibers & formation of lamellar bodies

13. II. Skin: Epidermis5 layers • Stratum Granulosum • Structure • 2 to 5 layers of flattened diamond shaped cells • Function • Prod’n of keratohyalin granules (makes cells look grainy) • Lamellar bodies release lipids from the cells • Cells die (nucleus & other organelles degenerate but keratin fibers and keratohyalin granules stay intact) • Stratum Lucidum • Structure • 3 to 5 layers of clear dead cells w/indistinct boundaries • Appear transparent & normally only in thick skin • Function • Dispersion of keratohyalin around keratin fibers

14. II. Skin: Epidermis5 layers • Stratum Corenum • Structure: • Most superficial layer of the epidermis • 25 or more layers of dead squamous cells (Cornified) • Fxn: • Provision of structural strength by keratin within cells Soft Keratin • Soft Keratin: • Keratin fibers + keratohyalin • Hard Keratin: • Found in nails & hair • Prevention of water loss via lipids surrounding cells • Sloughing off the most superficial layers resists abrasion • Desmosomes\ eventually break • XSV sloughing  dandruff

15. II. Skin: Thick and Thin Skin Thick Skin Classified based on the structure of the epidermis “Thickness of the skin” (Epi + Dermis) varies dependent on location ex/eyelid = 0.5mm shoulder/back = 5mm Skin subjected to XSV friction or pressure will eventually develop a callus (extra corneum) and these can develop on thick or thin skin Corn cone shaped callus that extends deep into epidermis and can be painful Thin Skin • All 5 epidermal layers & stratum corneum has many extra layers of cells • Found in areas subjected to pressure & friction • Palms, fingers, & soles • 4 epidermal layers • Covers the rest of the body • Granulosum often consists of only 1 or 2 layers • Hair is only found on thin skin. AP1 Chapter 5

16. II. Skin: Skin Color • Skin color is determined by: • Pigments w/in the skin • Blood circulating thru the skin • Thickness of the Stratum Corneum AP1 Chapter 5

17. II. Skin: Skin Color- Melanin • Group of pigments responsible for skin, hair, & eye color • Provides UV protection • High Melanin: • Freckles, moles, nipples, areolae of the breasts, axillae, & genitallia • Low Melanin: • Lips & palms • Originates from tyrosine & can be Ded into several different pigments ranging from black/brown to red/yellow Pg 156 Figure5.4 AP1 Chapter 5

18. Melanin production is based on 3 things II. Skin: Skin Color- Melanin • Genetic Factors • Different races or those w/in the same race • Amounts & types of melanin prod’d • Size, #, & distribution of melanosomes • # of melanocytes usually doesn’t D but amount of melanin prod’d does • 1 mutation can lead to albinism • Exposure to light • Darkens the melanin that is present & stimulates the prod’n of more • Hormones • Pregnancy induces the prod’n of estrogen & melanocyte stimulating hormone…thus increasing melanin prod’n • Line down middle of the belly, darkened nipples, areolae, & genetalia, mask of pregnancy • Addison’s disease can also cause D in color AP1 Chapter 5

19. II. Skin: Skin Color Erythema Carotene Yellow pigment found in plants (corn & carrots) Usually ingested and used as a source of Vit A XS ingestion can cause a discoloration (thus turning the skin yellow-orange) • Bld flowing thru skin imparts a reddish hue • Induced by: • Inflammatory response • Colds, blushing, flushing when angry or hot • Decrease in bld flow (shock) can make skin pale • Cyanosis: blue tint b/c of lack of O2 AP1 Chapter 5

20. II. Skin: Dermis • CT with a few adipocytes & macrophages as well the primary fiber is collagen • Compared to hypodermis the bld vessels & adipose is minimal • Present: • Nerve endings • Hair follicles • Smooth muscles • Glands • Lymphatic vessels • If skin is overstretched dermis may rupture leaving epidermal scars called  stretch marks • Nerve endings • Free nerve endings: • Pain, itch, tickle, temp • Hair follicle receptors • Light touch • Pacinian Corpuscle • Deep pressure • Meissner Corpuscle • Detect simultaneous stimulation on 2 points on the skin • Ruffini End organs • Continuous touch or pressure

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22. II. Skin- Dermis 2 major layers • Reticular Layer • Deep layer composed of DICT • Continuous w/hypodermis & forms a mat of irregularly arranged fibers that are resistant to stretching in many directions • Cleavage/tension lines elastin & collagen arrangement that prod patterns in skin (Stitching) • Papillary Layer • Superficial layer containing dermal papillae that extend toward the epidermis • Contains bld vessels that supply epi w/nutrients & removes wastes as well as aiding in body temp regulation • Thick skin responsible for finger prints wh/ fxn in increasing friction & improving grip AP1 Chapter 5

23. III. Hypodermis a.k.a. Subcutaneous tissue a.k.a. Superficial Fascia AP1 Chapter 5

24. III. Hypodermis • House Foundation Skin Hypodermis • Attaches to underlying bone & muscle, and supplies upper layers w/bld vessels & nerves • Matrix Loose CT, collagen & elastic fibers • Cells: fibroblasts, adipose cells, & macrophages • ~ ½ of the bodies adipose is stored here • Fxns: insulation, energy, & padding • Amount varies with age and sex • Babies have more than adults • Women more than men in hips and breasts • Body shape can also change w/ fat stores AP1 Chapter 5

25. IV. Accessory Skin Structures Hair Glands Nails AP1 Chapter 5

26. IV. Accessory Skin Structures: Hair Figure 5.6 pg 159 • Hair is found almost every where except: • Palms, soles, lips, nipples, external genitalia, & distal segments of the fingers & toes • Hair types: • Lanugo • 5th-6th mo of fetal development • Delicate unpigmented hair • Terminal Hairs • Near birth • Long course pigmented hair replaces lanugo on scalp, eyelids, & eyebrows • Vellus Hairs • Replace rest of body hair • Short, fine, usually unpigmented • Puberty: terminal hair replaces that of armpit (axillary) and pubic regions [Wicks/protects from abrasion] • Men chest, legs, arms  90% terminal hair • Women 35% AP1 Chapter 5

27. IV. Accessory Skin Structure: Hair Hair Structure Hair shaft: protrudes above the surface Hair Root: located below the surface Hair Bulb: expanded base of root 3 concentric layers to hair root/shaft Medulla Central axis of the hair 2-3 layers of cells w/soft keratin Cortex Forms bulk of hair cells contain hard keratin (more S in make-up) Cuticle Single layer of cells that forms hair surface & overlap like shingles AP1 Chapter 5

28. IV. Accessory Skin Structure: Hair Hair Structure Hair follicle consists of: Dermal Root Sheath Portion of the dermis that surrounds the Epi root sheath Epithelial Root Sheath External All strata found in thin skin toward hair shaft but decreases as it goes down until it is only the stratum basale Internal Holds hair in place, and when hair is pulled it usually can be seen at the base AP1 Chapter 5

29. IV. Accessory Skin Structure: Hair Hair Structure Inside of the hair bulb Matrix: mass of undifferentiated epithelial cells which prod the hair & the epithelial root sheath. Hair Papilla: Dermis of the skin projects into the hair bulb at the base and contains blood vessels that provide nourishment for the cells of the matrix Hair Color • Melanin is prod’d by melanocytes w/in hair bulb matrix & is passed to keratinocytes in hair cortex & medulla • Varying amounts & types of melanin cause different shades • W/ age amount of melanin in hair can decrease; causing hair color to fade AP1 Chapter 5

30. IV. Accessory Skin Structure: Hair Hair Growth Eyelashes: 30 days growth 105 days rest Scalp: 3 years growth 1-2 years rest Ave. hair growth is 0.3mm a day Max hair length is determined by rate of hair growth & length of growing phase • Hair is prod’d in cycles • Growth Stage • Hair is formed by matrix cells that differentiate, become keratinized and die • Hair grows longer as cells are added to the base • Resting Stage • Hair growth stops hair follicle shortens & hold hair in place AP1 Chapter 5

31. IV. Accessory Structures: Muscles • Arrector Pili • Extend from the dermal root sheath of the hair follicle to the papillary layer of the dermis • This takes the hair from oblique angle to a more perpendicular angle to the skin surface (gooseflesh) • Cold or scared AP1 Chapter 5

32. IV. Accessory Skin Structures: Glands • Major skin glands: • Sebaceous glands • Sudoriferous • Eccrine • Apocrine AP1 Chapter 5

33. IV. Accessory Skin Structures: Glands • Major skin glands: • Sebaceous glands • Located in the dermis • Simple/Compound alveolar glands that produce sebum • Oily white substance rich in lipids • Holocrine glands b/c lysis & death of cells that become part of secretion • Connected via duct to hair follicle • Prevents drying & protects against some bacteria • Very few open to skin surface AP1 Chapter 5

34. IV. Accessory Skin Structures: Glands • Major skin glands: • Sudoriferous • Sweat glands • Eccrine • Most common type found almost everywhere (including hands & soles of feet) • Simple, coiled, tubular glands that open to skin surface through pores • 2 regions: • Deep coiled region (dermis) • Produces sweat (isotonic fluid that includes water, some salt, small amounts of urea, ammonia, uric acid, & lactic acid) • Duct (passes to surface) • Help regulate temperature • Apocrine AP1 Chapter 5

35. IV. Accessory Skin Structures: Glands • Major skin glands: • Sudoriferous • Sweat glands • Eccrine • Apocrine • Simple coiled tubular glands that open into hair follicles superficially to sebaceous glands • In humans they are found in the axillae, genitalia, and around the anus • Do not regulate temperature • Only become active at puberty as a result of sex hormone stimulation • May be a sign of sexual maturity. AP1 Chapter 5

36. IV. Accessory Skin Structures: Glands Other glands • Ceruminous Glands: • modified sweat glands located in the ear canal produce cerumen (earwax) to protect eardrum by preventing entry of dirt or small insects • Mammary Glands: • Modified apocrine sweat glands in breasts designed to produce milk AP1 Chapter 5

37. IV. Accessory Skin Structures: Nail • Distal ends of primate digit covered in nail • Fxn: • Protection • Manipulation & grasping of small objects • Scratching • Nail consists of 2 major parts: • Nail Root (Proximal portion): covered by skin • Nail Body (Distal Portion): visible portion AP1 Chapter 5

38. IV. Accessory Skin Structures: Nail • Nail fold: Flaps of skin that cover the root & lateral edges • Nail grove: holds edges of nail in place • Eponychium: cuticle • Hyponychium: thickened portion of stratum corneum beneath the free edge of the nail body • Nail Root extends distally from nail matrix, which produces the majority of the nail • Nail bed holds the nail body • Lunula- cresent shaped area at the base of the nail that has almost no color because it is thicker that the rest of the nail AP1 Chapter 5

39. V. Summary of IS fxns Protection Sensation Temperature regulation Vitamin D Production Excretion AP1 Chapter 5

40. V. Summary of IS Fxns 1. Protection 2. Sensation Skin contains sensory receptors for: Pain Touch Hot Cold Pressure These allow for proper response to the environment • Protects against abrasion, UV-light, prevents entry of microorganisms, helps regulate body temperature, & prevents water loss. • Hair protects against abrasion & blocks UV-light & is a heat insulator • Nails protect the ends of digits AP1 Chapter 5

41. V. Summary of IS Fxns 3. Temperature Regulation 4. Vitamin D Production Skin exposed to UV-light produces cholecalciferol, wh/ is modified in the liver & then in the kidneys to form active Vit D. Vit D increases blood Ca levels by promoting Ca uptake from the intestine, the release of Ca from the bone, and the reduction of Ca loss from the kidneys. • Thru dilation & constriction of blood vessels, the skin controls heat loss from the body • Sweat glands produce sweat, which evaporates & lowers body temperature AP1 Chapter 5

42. V. Summary of IS Fxns 5. Excretion • Skin glands remove small amounts of waste products (i.e. urea, uric acid, & ammonia) but are not important to excretion like the kidneys. AP1 Chapter 5

43. VI. FX of aging on IS AP1 Chapter 5

44. VI. Effects of aging on the IS • As the body ages, blood flow to the skin declines, thus skin becomes thinner & elasticity is lost • Sudoriferous & sebaceous glands are less active and the number of melanocytes also decreases AP1 Chapter 5