Integumentary System

1. Integumentary System • Introduction to the Integument • The Epidermis • The Dermis • The Subcutaneous Layer • Accessory Structures • Local Control of Integumentary Function • Aging and the Integumentary System

2. Introduction • The Integument: • Large, highly complex organ (?) • Structurally integrated organ system (?) • Factoids: • 16% of body weight • 1.5 – 2.0 m2 surface area • Affected by other body systems • Affected by emotional state 

3. Learning Objectives • Integument: • List the major components of the integumentary system • Discuss the tissue types of the integument • FunctionsoftheIntegument: • Describe six functions of the integument

4. Integumentary System:Major Components • Cutaneous Membrane: • Epidermis • stratified squamous epithelium • basement membrane • Dermis • loose connective tissue • dense irregular connective tissue • Accessory Structures: • hair • glands • nails

5. Integumentary Components • Epidermis: • superficial epithelium • Dermis: • connective tissue • accessory structures • Subcutaneous Layer: • connective tissue • superficial fascia

6. Integumentary Function • Protection – of underlying tissues & organs • Excretion – of salts, H2O, & waste • Maintenance – of normal body temperature • Synthesis – of vitamin D3 • Storage – of nutrients (lipids, protein) • Detection – of touch, pressure, temperature change, & pain

7. The Epidermis • Layers of the Epidermis • Skin Color • The Epidermis & Vitamin D3 • Epidermal Growth Factor

8. Learning Objectives • EpidermalLayers: • List & describe the layers of the epidermis in order from deepest to most superficial • Identify the dominant proteins of epidermal cells • Distinguish between “thin” & “thick” skin

9. Epidermis

10. Layers of the Epidermis • Stratum Germinativum (a.k.a., stratum basale) • Stratum Spinosum • Stratum Granulosum • Stratum Lucidum (in specific loci) • Stratum Corneum Note: order from deepest to most superficial

11. Stratified Squamous Epithelium

12. Stratum Germinativum • “sprouting layer” • deepest layer • 1 layer of cuboidalstem cells • firmly attached to basement membrane • epidermal ridges extend into dermis • melanocytes present epidermal ridge

13. Stratum Spinosum • “spiny layer” • above str. germinativum • 8-10 layers of roundedkeratinocytes bound together by desmosomes • Langerhans cells present

14. Stratum Granulosum • “granular layer” • above str. spinosum • 3-5 layers of ovoidkeratinocytespacked with keratin-filled granules • nuclei & other organelles begin to disintegrate • cell membranes become impermeable

15. Stratum Lucidum • “glassy layer” • above str. granulosum • 2-3 layers of flattened keratinocytes • cells very densely packed together • occurs only on the palms of the hands & soles of the feet

16. Stratum Corneum • “horny layer” • most superficial layer • 15-30 layers of flatkeratinocytes cells firmly connected by desmosomes • packed with keratin • relatively dry & water resistant • Cells are dead

17. Thin Skin -v- Thick Skin

18. Thin Skin -v- Thick Skin

19. Skin Color • Pigment Components • Non-pigment Component • Pigment Functions • Melanocyte Structure & Function • Skin Color Differences

20. Learning Objectives • SkinColor: • Discuss the factors that contribute to skin coloration • Name the sources of skin pigments • Discuss the effects of ultraviolet radiation on the skin and the protective role played by melanocytes

21. Skin Color • Pigment Components: • Melanin • brown – yellow-brown – black pigment • source – melanocytes • Carotene • orange-yellow pigment • accumulates in epidermal and adipose tissues of skin from • source – plants, esp. orange & yellow colored fruits & vegetables

22. Skin Color • Non-pigment Component: • Hemoglobin • dermal circulation • reddish tint due to oxyhemoglobin • cyanosis - bluish tint due to non-oxygenated hemoglobin

23. Skin Color • Pigment Functions: • Melanin • protection from UV radiation • melanosomes concentrate around cell nuclei • Carotene • conversion to vitamin A (1) normal maintenance of epithelia (2) synthesis of photoreceptor-receptor pigments in eye

24. Melanocytes • Melanocyte Structure • Long processes weave from str. germinativum into str. spinosum & granulosum • Melanocyte Function • Packages melanin into vesicles - melanosomes • Melanosomes transferred to keratinocytes • Melanin absorbs potentially harmful UV radiation

25. Skin Color • Differences in skin color: • Number of melanocytes is equivalent in all races & ethnic groups • Skin tones due to • amount of melanin produced by melanocytes • melanin color • persistence of melanosomes in upper layers of the epidermis

26. Vitamin D3 & Epidermal Growth Factor • Vitamin D3 Structure & Production • Vitamin D3 & Calcitriol Function • EGF Structure & Function

27. Learning Objectives • VitaminD3: • Discuss the production & importance of vitamin D3 • EpidermalGrowthFactor: • Explain how EGF contributes to maintenance of the integument

28. The Epidermis & Vitamin D3 • Vitamin D3: a.k.a., cholecalciferol • steroid • converted to calcitriol • calcitriol promotes Ca2+ & PO43- uptake by small intestine • essential for normal bone growth & maintenance

29. The Epidermis & Vitamin D3 • Process: • UV light converts cholesterol-related steroid to vitamin D3 • vitamin D3 travels in circulation to liver where it is converted to intermediate • Intermediate travels to kidney where it is converted to calcitriol • calcitriol promotes intestinal cell permeability to calcium and phosphate

30. Epidermal Growth Factor • EGP: • peptide hormone • produced by salivary glands & duodenum of small intestine • widespread effects on epithelia • specific effects on epidermis

31. Epidermal Growth Factor • Effects on Epidermis: • Promotes cell division in str. germinativum & spinosum • Accelerates keratin production • Stimulates epidermal development & epidermal repair • Stimulates synthesis & secretion by epidermal glands

32. Physics of Electromagnetic Radiation • To View Video: • Move mouse cursor over slide title-link • When hand appears, click once • ASX Video plays about 30 min

33. The Dermis • Dermal Organization • Dermal Circulation • Dermal Innervation

34. Learning Objectives • DermalOrganization: • List the layers of the dermis from most superficial to deepest • Distinguish between the structure and function of the dermal layers • DermalCirculation& Innervation: • Name sensory structures of the dermis and describe their functions

35. Dermal Organization

36. Layers of the Dermis • Papillary Layer • Reticular Layer Note: order from most superficial to deepest

37. Papillary Layer Papillary Layer Characteristics • loose connective tissue • capillaries – papillary plexus • sensory nerve endings • dermal papillae – ↑ surface area to bind overlying epidermis to dermis

38. Reticular Layer Characteristics • dense irregular connective tissue • bound to papillary layer above & subcutaneous layer below by bundles of collagen fibers • capillaries – cutaneous plexus

39. Dermal Organization • extracellular protein fibers • collagen – strength • elastin – permits stretching • all cells of connective tissue proper: adipocytes, fibroblasts, macrophages, etc • accessory organs of epidermal origin extend into dermis: hair follicles, sweat & sebaceous glands • contains blood vessels, lymph vessels & nerves loose connective tissue proper dense irregular connective tissue

40. Dermal Reticular Layer loose connective tissue blood vessel collagen fiber bundles (c.s.) smooth muscle

41. Dermal Organization Papillary Plexus Papillary Layer Reticular Layer Cutaneous Plexus

42. Wrinkles & Stretch Marks • Wrinkles - reduced elastin: • aging • dehydration • hormones • UV radiation • Stretch marks – damaged elastin • pregnancy • weight loss after weight gain

43. Lines of Cleavage • due to parallel arrangements of elastin & collagen fibers in areas of the skin • Function – to resist applied forces from muscle contraction, joint movement, etc • a cut parallel to cleavage lines will remain closed; a cut perpendicular will remain open due to elastic fiber recoil Typical incision for appendectomy

44. Skin Innervation • Nervous System Control: • blood flow • gland secretion rates • Sensory Function: • root hair plexuses – hair displacement by wind, contact • Pacinian corpuscles – deep pressure • Merkel’s discs – fine touch; light pressure • Ruffini corpuscles – (in deep dermis) heavy pressure; distortion of skin • Meissner’s corpuscles – fine touch; light pressure; low frequency vibration • free nerve endings – touch; pressure; pain; temperature change

45. Learning Objectives • SubcutaneousOrganization: • Describe the structure of the hypodermis and identify it as a general type of membrane • Subcutaneous Function: • Explain the function of the hypodermis

46. The Subcutaneous Layer • Structure: • loose connective tissue • abundant adipose cells • Function: • stabilize position of the skin • energy reserve • protection from mechanical shock • thermal insulation

47. Subcutaneous Layer Properties • elastic • few blood vessels • no vital organs • good diffusive properties • excellent for subcutaneous injection

48. Subcutaneous Organization Reticular Layer Cutaneous Plexus Loose Connective Tissue Subcutaneous Layer Adipose Cells

49. Accessory Structures • Hair Follicles & Hair • Glands in the Skin • Nails

50. Learning Objectives • HairFollicles&Hair: • Identify the structures of a typical hair follicle • Explain how hair is produced and describe mechanisms that determine hair texture and color