The integumentary system

1. Chapter 5 The integumentary system

2. The integument is either considered an organ or organ system. (The terms integument & integumentarysystem are interchangeable) I. Introduction

3. Components of the I.S.: • Cutaneous membrane: • Epidermis- superficial epithelium • Dermis- underlying connective tissues • Accessory structures: • Hair • Nails • Exocrine glands

4. Subcutaneous layer (aka. hypodermis or superficial fascia): • Loose connective tissue located below the dermis • Not necessarily considered part of the integument

5. Protection of underlying structures • Excretion of salts, water & wastes • Maintenance of body temperature • Synthesis of vitamin D3 (used in Ca absorption) • Storage of nutrients • Detection of stimuli C. General functions of the skin:

6. Physiology: provides physical protection, prevents fluid loss, and helps keep microorganisms out of the body Anatomy: stratified squamous epithelium II. The epidermis

7. Keratinocytes- the most abundant cells in the epidermis • Thickskin (on hands & feet) has 5 layers • Thin skin (everywhere else) has 4 layers

8. D. Layers of the epidermis (deep to superficial)

9. Stratum Germinativum (aka. Stratum Basale) • Firmly attached to the basement membrane • Epidermal ridges & dermal papilla form ridges & valleys • Increases surface area • Creates contours on the skin surface (ex. fingerprints)

10. Cell types: • Basal cells: germinative cells that replace keratinocytes • Merkel cells: sensitive to touch • Melanocytes: pigment cells

11. Stratum Spinosum “spiny layer” • 8-10 layers of cells bound together by cell junctions • Contain Langerhans cells- part of the immune response

12. Stratum Granulosum “grainy layer” • 3-5 layers of keratinocytes • most cells stop dividing and start producing keratin and keratohyalin(fibrous proteins) • Cells eventually die & become less permeable • StratumLucidum • Found only in thick skin of the palms & soles • Cells are flattened, densely packed and filled w/ keratin

13. Stratum Corneum • Located at the surface of both thick and thin skin • 15-30 layers of keratinized cells • Usually shed in sheets, not individually • Cells take 15-30 days to travel from the stratum germinativum to the stratum corneum and about 2 weeks until they are shed or washed away • Normally relatively dry, inhibiting the growth of microorganisms

14. Thick Skin

15. This layer is water resistant, not waterproof: • Insensible perspiration: interstitial fluid slowly moves to the surface to evaporate (~500 ml/day) • Damage to the epidermis can increase fluid movement • Blister- when damage separates layers of the epidermis & fluid accumulates in pockets • Greater damage can cause greater water loss, like in burn victims • Sitting in water causes water to move in (freshwater) or out (salt water) due to osmosis

16. Please answer the 4 questions on the bottom of page 151 for tomorrow. Try this quiz

17. Skin pigment composition & concentration • Carotene • Orange-yellow pigment • Accumulates inside epidermal cells & also in fatty tissues of the dermis • Most apparent in cells of the stratum corneum of light-skinned people • Also found in vegetables like carrots & squash • Can be converted to vitamin A (needed for maintenance of epithelia & the eyes) E. Skin Color

18. Melanin • Brown, yellow-brown or black pigment produced by melanocytes • The effect on skin color depends on where it is released in the epidermis: • In white people, it is released in the stratum germinativum & stratum spinosum • In black people, it is also released in the stratum granulosum • Protects the epidermis and dermis from ultraviolet radiation from sunlight, which can cause burns, premature wrinkles and DNA mutations leading to cancer

19. The dermal blood supply • Blood contains the pigment hemoglobin, which turns bright red when it binds with O2 • Most obvious in light-skinned people • Variations: • Blushing or inflammation- blood vessels dilate • Pale skin- reduced blood supply • Cyanosis- sustained reduction in blood supply in response to cold or problems such as heart failure or severe asthma

20. The Epidermis and Vitamin D3 • When exposed to sunlight, cells in the stratum spinosum and stratum germinativum make vitamin D3 • The liver converts vitamin D3 into a product used by the kidneys to make the hormone calcitriol. • Calcitriol is needed for the absorption of calcium and phosphorous by the small intestine

21. Please answer the 3 questions on the top of page 154.

22. Dermal Organization • Two major components: • Papillary Layer (superficial) • Consists of loose connective tissue • Contains capillaries & sensory neurons • Reticular Layer (deep) • Meshwork of dense irregular connective tissue (collagen & elastin) • Bundles of collagen fibers extend into the layers above and below, so boundary is indistinct • Also contains blood vessels and nerves III. The dermis

23. Collagen fibers are strong & resistant to stretching • Elastic fibers permit stretching and will then return to the original length • The skin will stretch only as far as the collagen fibers will allow, thus preventing tissue damage • Water in the skin also allows flexibility • Aging, hormones & damage from UV rays reduces the amount of elastin in the dermis, producing wrinkles & sagging skin • Stretch marks occur from extensive distortion of the dermis (pregnancy, weight gain, growth spurts) 2. Wrinkles & stretch marks

25. Most collagen and elastic fibers at any one location are arranged in parallel bundles • The orientation of bundles depends on stresses that occur during normal movements • The resulting pattern establishes lines of of cleavage of the skin • A surgeon will cut parallel to the lines instead of perpendicular to them to keep the cut from pulling open 3. Lines of Cleavage

26. The Dermal Blood Supply • Read more about this on page 155 in your text • Ulcers or bedsores may affect bedridden or immobile people • Circulation is cut off when blood vessels are pressed against deeper structures for extended periods of time • Eventually this will lead to necrosis (tissue death) • Birthmarks & “port wine stains” occur from tumors in the dermal blood supply b. Dermal circulation & innervation

28. Nerve fibers control: • Blood flow • Adjust gland secretion rates • Monitor sensory receptors in the dermis & deep epidermis • The dermis & deep epidermis contains sensory receptors for: • Light touch • Pain • Temperature • Deep pressure • vibrations 2. The Innervation of the skin

29. Please answer the 2 questions near the bottom of page 156.

30. Stabilizes the position of the skin relative to underlying tissue (muscle, organs), while permitting independent movement Consists of loose connective tissue w/ lots of fat cells and elastic fibers Only the superficial region contains large arteries & veins Some drugs are administered by a hypodermic needle to the deep hypodermis iV. The subcutaneous layer (Hypodermis)

31. “Baby fat” in infants & children: • Reduces heat loss • Energy reserve • Padding • In adults fat is distributed: • Men: neck, arms, lower back, buttocks, abdomen • Women: Breasts, buttocks, hips, thighs, abdomen

32. Hair • Location: Project into the dermis & usually into the hypodermis • Functions: • Protect skin from UV rays • Provide padding • Guard entrances to the body • Provide sensitivity to touch • Provide insulation • Arrectorpili muscles cause goosebumps- hairs stand up • Doesn’t really insulate humans v. Accessory structures

33. Types of hairs: • Vellus Hairs: fine “peach fuzz” • Terminal Hairs: heavy, darker • Hair color: • Melanocytes • White hair: lack of pigment + air bubbles • Growth & Replacement of Hair: * read about this on page 159 (fyi only)

34. Hair Structure: • Hair Follicles: • Hair Papilla: • Hair Bulb: • Hair Matrix: • Medulla: • Cortex: • Cuticle: • Root: • Hair Shaft: • Root Hair Plexus:

35. Function: protect the exposed tips of fingers and toes • Nail Structure: (know these parts) • Nail Body: • Nail Bed: • Nail Root: • Cuticle (Eponychium): • Lunula: • Nail Grooves & Nail Folds: • Free Edge: • Hyponychium: B. Nails

36. Cells that produce nails can be affected by conditions that alter body metabolism • Changes in the nails can help with diagnoses: * Examples on page 162

37. Sebaceous Glands (Oil Glands) • Holocrine glands • Sebum- a waxy, oily substance secreted into hair follicles and onto the skin • Arrectorpilli muscles contract to release secretion • Sebum lubricates hair and skin and prevents bacterial growth • (Shampoo removes sebum, which can dry the hair) • Sebaceous Follicles- large sebaceous glands w/o hairs • Found in skin of the face, back, chest, nipples & male sex organs • Glands can become infected with bacteria or blocked with sebum and then infected (ex. acne, folliculitis) C. Glands

38. Apocrine Sweat Glands • Found in armpits, nipples & groin • Begin secreting a sticky, cloudy secretion at puberty (yay!) • Merocrine Sweat Glands (aka Eccrine Sweat Glands) • More numerous and widely distributed (2-5 million per adult) • Palms and soles have the most • Secrete sensible perspiration • 99% water along w/ salt, nutrients & wastes • Functions: • Cools the skin • Excrete water & other substances (up to 1 gallon/hour!) • Discourages growth of microorganisms 2. Suderiferous Glands (sweat Glands)

39. Other Integumentary Glands • Mammary Glands • Ceruminous Glands- secrete cerumen (ear wax)

40. The skin can regenerate effectively because stem (germ) cells are found in both epithelial and connective tissues. vi. Injury and Repair

41. Bleeding occurs, mast cells trigger inflammation • A blood clot (scab) forms to restore integrity and keep bacteria out. Cells from the stratum germinativum migrate along the sides of the wound. Macrophages patrol for pathogens & debris. B. Four Stages oF Regeneration

42. The clot will begin disintegrating while it is being pushed up by new tissue growth. Fibroblasts produce large amounts of inflexible collagen fibers to replace lost connective tissue. (Scar tissue) • Scab is shed. Scar tissue gradually evens out with epidermis.

43. Check out page 164 for a list of affects aging has on the components of the integumentary system. vii. Aging & the integumentary system