The Integumentary System

1. The Integumentary System Anatomy & Physiology Chapter 4

2. Classification of Body Membranes • cutaneous membranes • skin • mucous membranes • covers body cavities that open to exterior • mucosa • serous membranes • serosa • covers ventral cavities & organs in them • visceral & parietal peritoneum • synovial membrane • no epithelial cells • made of areolar CT • line capsules surrounding synovial joints, tendon sheaths & bursae Epithelial Connective Tissue

3. Integumentary System • Includes: • Skin • Nails • Hair • Sweat & Oil Glands

4. Integumentary System Functions: • protection • body temperature homeostasis • excretion of urea& uric acid • part of vitamin D synthesis

5. Protection • of deep tissues from mechanical damage • physical barrier by keratin (toughens skin) • contains pressure receptors: send sensory message to CNS; heat & cold receptors  CNS • from chemical damage • skin is relatively impermeable (keratin) • contains pain receptors  CNS • from bacterial invasion • skin secretions are acidic so inhibit bacterial growth; phagocytes in skin ingest invaders • from UV radiation • melanin made by melanocytes in skin protects nuclei

6. Functions of Skin • dessication • keratin & other substances provide waterproofing • body temperature homeostasis • when body overheated blood flow to skin increases & some heat radiates off body, sweating • when body cold less blood flows to skin, more to trunk, goose bumps

7. Functions of Skin-2 • excretory function: sweat contains urea, uric acid (breakdown products of proteins) • helps in synthesis of Vitamin D • sunlight on skin activates conversion of pre-vitamin D  vitamin D

8. Vitamin D

9. Structure of the Skin • made of 2 kinds of tissues • Epidermis • Dermis

10. Epidermis • made of stratified squamous epithelium • some keratinized, some not • avascular • Cells: • Keratinocytes • majority of cells • make keratin • Melanocytes • Langerhans Cells • Immune System

11. Epidermal Layers • stratum basale • deepest layer • constantly undergoing cell division/ cells pushed upward • stratum spinosum • stratum granulosum • stratum lucidum (only in thick skin) • clear, flatter, more keratin • stratum corneum (cornified = keratinized) • outermost layer/ 20-30 dead cells thick

12. Epidermal Layers

13. Stratum Corneum • dead cells flake off steadily continually being replaced by cells gradually pushing up from the stratum basale

14. Melanin • pigment • (yellow to brown to black) • produced by melanocytes • most are in stratum basale • cells stimulated to make more melanin when skin exposed to sunlight • shields DNA from damaging effects of UV radiation freckles & moles: seen where melanin concentrated in 1 spot

15. Freckle

16. Excessive Sun Exposure • causes elastic fibers to clump  leathery skin • depresses immune system • UV radiation damages DNA  skin cancer

17. Dermis • a strong, stretchy envelope that helps to hold the body together • leather is the dermis of whatever animal it was made from • made of dense CT • 2 regions: • Papillary • Reticular

18. Dermis: Papillary Layer • upper dermis • dermal papillae: uneven projections into lower epidermis that contain: • capillaries • pain receptors • touch receptors: Meissner’sCorpuscles • in thick skin: form ridges (fingerprints) that improve gripping ability

19. Dermal Papillae

20. Dermis: Reticular Layer • deepest skin layer • Contains: • sweat & oil glands, hair follicles, blood vessels • Pacinian corpuscles (deep touch receptors) • many phagocytes • fibers: elastic: give young skin elasticity collagen: make dermis tough& keep skin hydrated by binding to water

21. Reticular Layer

22. Body Temperature Homeostasis • Skin plays major role in maintaining homeostasis of temperature: • Overheated: • Blood vessels in dermis dilate  increases blood flow to skin  heat radiates off body • Hypothermic: • Blood vessels in skin constrict  decreases blood flow to skin less heat loss thru skin

23. Decubitus Ulcers • aka bedsores • due to extended restriction of normal blood supply to skin

24. Skin Color • 3 pigments contribute to skin color: • Melanin • amount & kind (yellow  black) • Carotene • orange – yellow pigment • stratum corneum & subcutaneous layers • Hemoglobin • amount O2 bound to it in RBCs in dermal blood vessels • has greater affect in light skinned people

25. Skin Color in Sickness & in Health • cyanosis: blue hue to skin; due to poorly oxygenated blood • erythema: redness, due to increased blood flow (infection, inflammation); burn, HT, blushing • pallor: paleness, due to emotions, anemia, low BP, decreased blood flow • jaundice: yellow; usually from liver disease (not clearing bilirubin) • hematomas: bruising (bleeding under skin)

27. Appendages of the Skin • Glands: • all are exocrine glands (secrete product thru ducts) • secrete their product to skin • 2 groups: • Sebaceous glands • Sweat glands

28. Sebaceous Glands • are oil glands • all over skin except palms& soles • ducts mostly empty onto hair follicle rest onto skin surface

30. Sebaceous Glands • sebum: product secreted by sebaceous gland • made of oils & fragmented cells andantibacterials • function: lubricant’ keeps skin soft & keeps hair from getting brittle • increase activity during puberty (reason skin becomes oilier)

31. Sebaceous Glands Gone Bad • if ducts become blocked  whiethead forms  material in it oxidizes & dries  blackhead • Acne: active infection of sebaceous glands, mild to severe causing permanent scarring • Seborrhea: cradle cap; overactivity of sebaceous glands pink raised lesions  yellow to brown crust

32. SEBACEOUS GLANDS ACNE SEBORRHEA

33. Sweat Glands • also known as sudoriferous glands • all over skin • 2 types: • Eccrine sweat glands • Apocrine sweat glands

34. Eccrine Sweat Glands • all over body • produce sweat • clear • pH 4 – 6 (being acidic  bacteriostatic) • mainly water (+ NaCl, NH3, urea, uric acid, & lactic acid)

35. Eccrine Glands

36. Eccrine Glands • typically sweat released from duct thru pore (different from facial “pores”; those are openings of hair follicles)

37. Eccrine Sweat Glands • important part of body’s heat-regulating equipment • + nerve endings to cause sweat to be released whenever external temperature or body temperature is high • when water in sweat evaporates it cools body • important to keep body temperature w/in few degrees of 37 ◦C or it malfunctions

38. Apocrine Sweat Glands • mostly in axilla & genital areas • ducts empty onto hair follicles • secretions: fatty acids, proteins, +what is in eccrine sweat • if colonized with bacteria will have odor, otherwise odorless • begin to function during puberty (stimulated by androgens)

39. Appocrine Glands