Integumentary system

1. Integumentary system Fowler A&P

2. Integumentary System • Integument means “covering” • Comprised of • Skin • Accessory Components (hair, nails, glands associated with skin)

3. Integumentary System (Skin) • surface area of 1.5 to 2 square meters • weighs 9 to 11 pounds • varies in thickness from1.5–4mm • every square centimeter (cm) of the skin contains: • 70 cm of blood vessels, 55 cm of nerves, 100 sweat glands, 15 oil glands, 230 sensory receptors, and about 500,000 cells that are constantly dying/being replaced • pliable, tough, waterproof, insulates, cushions • without our skin, we would quickly fall prey to bacteria and perish from water and heat loss

4. Skin Cell

5. Basic Skin Functions • Provides Protection from: • mechanical damage (bumps and cuts) • chemical damage (acids, bases, poisons) • thermal damage (heat and cold) • UV radiation (sunlight) • invasion (bacterial)

6. Focus Questions-Read and Take Notes • What are the basic skin functions? • What are the 3 distinct regions w/in the integumentary system?

7. Basic Skin Functions • Sweat glands regulate heat loss • Mini-excretory system • Manufactures proteins important in immunity • Synthesizes vitamin D • Contains sensory receptors for touch, pressure, temperature, and pain

8. Distinct Regions • Skin comprised of 3 regions • Epidermis • Outermost protective layer • Dermis • Hypodermis (subcutaneous/fat)

9. Epidermis • Outside layer of skin • Avascular (no blood vessels) • Thick to prevent water loss • Composed of epithelial cells • Ex. Include keratinocytes & melanocytes

10. Keratinocytes  • produce keratin (protein with protective and structural properties) • arise in the deepest part of the epidermis • undergo almost continuous mitosis • millions of these cells rub off every day • totally new epidermis every 35 to 45 days

11. Melanocytes • specialized epithelial cells that synthesize the pigment melanin  • skin color due to differences in melanocyte activity  • freckles/moles are where melanin is concentrated in one spot

12. 5 Layers of Skin w/in Epidermis

13. Stratum Basale (AKA stratum germinativum) • deepest • attached to the underlying dermis and receive nourishment • single row of cells representing the youngest keratinocytes • rapid division of these cells push daughter cells upward (growing layer) • 10% to 25% melanocytes

14. Stratum spinosum   • Several cell layers thick • Keratinocytes appear to have spines (prickly layer), are somewhat flattened and irregular in shape

15. Stratum Granulosum (“granular layer”)  • three to five cell layers • keratinocytes have flat granules (granular layer) of keratin that accumulate which helps in slowing water loss

16. stratum lucidum • appears as a thin translucent band (clear layer) just above the stratum granulosum • clear, flattened, dead keratinocytes • present only in thick skin

17. stratum corneum • 20 to 30 cell layers thick • 3/4 of the epidermal thickness • cornified/horny cells (horny layer) shed from the scalp and flakes slough off dry skin

18. Guided Practice • Create a way to remember the layers of the epidermis: • Deep to Superficial • Superficial to Deep

19. Bellwork • Which parts of the body have 5 layers in the epidermis? Describe this area. • Objectives: • Differentiate between the layers of the epidermis • Differentiate between the regions of the integumentary system (specifically dermis and hypodermis)

20. Independent Practice • Create a foldable for each of the 5 layers of the epidermis. Include layer name, features, and image of tissue.

21. Bellwork • Describe the functions of the Integumentary System. • Objectives: • Differentiate between the layers of the epidermis • Differentiate between the regions of the integumentary system (specifically dermis and hypodermis) • Identify appendages of the skin

22. Dermis • vascularized, contains a rich nerve supply, is a shock absorber, and anchors the skin • nutrients reach the epidermis by diffusion • two major layers – papillary and reticular

23. Papillary Layer • Superior surface has nipple-like projections called dermal papillae • Contains • Capillaries (blood vessels) • Nerve endings (pain receptors) • Touch receptors • Dermal ridges produce looped/whorled ridges on the epidermal surface • ridges increase friction • unique patterns (fingerprints)

24. Reticular Layer • deeper layer containing sweat glands, oil glands, and blood vessels • 80% of the dermis • pressure receptors • collagen fibers (toughness and attracts water to help the skin stay hydrated) • elastin fibers (provides elasticity)

25. Hypodermis • AKA subcutaneous fascia • Below dermis • Composed of connective and fatty tissues • anchors skin to underlying organs • Absorbs shock • Insulates deeper tissues

26. Skin Color  • 3 pigments contribute to skin color: melanin, carotene, and hemoglobin

27. Pigments

28. Melanin • only melanin is made in the skin • ranges in color from yellow to reddish-brown to black • stimulated to greater activity when we expose our skin to sunlight • prolonged sun exposure causes a substantial melanin buildup

29. Carotene • yellow to orange • accumulate in the stratum corneum and fatty tissue of the hypodermis • color is most obvious in the palms and soles, where the stratum corneum is thickest Hemoglobin • pinkish hue of fair skin reflects the red color of oxygenated hemoglobin

30. Guided Practice • Close read and take notes to identify the appendages of the skin. Be sure to focus on these topics: • Oil glands • Sweat glands • Eccrine • Apocrine • Hair/Hair follicles • Nails

31. Appendages of the Skin  • made in the epidermis – sudoriferous (sweat) glands, sebaceous (oil) glands, hair follicles/hair, and nails

32. 1. Sweat (sudoriferous) Glands • Formed by stratum germinativumand pushed deep into the dermis • Entire skin surface except the nipples and parts of the external genitalia • 2.5 million per person • Made up of Eccrine and Apocrine Glands

33. Eccrine Glands • more numerous • 99% water • abundant on the palms, soles of the feet, and forehead • secretion is commonly called sweat • major role is to prevent overheating • heat-induced sweating begins on the forehead • emotionally induced sweating begins on the palms, soles, and armpits

34. Apocrine Glands • confined to the axillary and genital areas • larger than eccrine glands • ducts empty into hair follicles • same basic components as true sweat, plus some fatty substances and proteins • milky or yellowish color • secretion is odorless • begin to function at puberty

35. Specialized Apocrine Glands • ceruminous glands • found in the lining of the external ear canal • secrete a rather sticky substance called cerumen, or earwax • thought to deter insects and block entry of foreign material  • mammary glands • specialized sweat glands • secrete milk

36. 2. Sebaceous (oil) Glands • formed by stratum germinativum and pushed deep into the dermis • found all over the body except palms and soles • small on the body trunk and limbs, but large on the face, neck, and upper chest • oily secretion called sebum secreted into a hair follicle or to a pore on the skin surface • softens/lubricates hair and skin, prevents hair from becoming brittle, and slows water loss from skin

37. 2. sebaceous (oil) glands • central cells of the gland accumulate lipids until they burst • stimulated by hormones • if blocked, whitehead forms • whitehead dries/darkens to form a blackhead • acne is an active inflammation of the sebaceous glands accompanied by pimples • caused by bacterial infection

39. 3. Hair Follicles/Hair • Follicle-site where hair is formed  • Follicles extend from the epidermis to the dermis • deep end of the follicle is expanded (hair bulb forms) • papilla protrudes into the hair bulb • the growth zone (matrix) in the hair bulb includes cells that actively divide to produce hair • bundle of smooth muscle cells called an arrector pili

40. 3. Hair Follicles/Hair • life span of hairs varies but follicles remain active for years (average is four) • eyebrow follicles remain active for 3-4 months • why eyebrows are never as long as the hairs on your head • rate of hair growth about 2 mm per week • hair pigment is made by melanocytes at the base of the hair follicle • gray or white hair results from decreased melanin production

41. 3. Hair Follicles/Hair • lips, nipples, parts of the external genitalia, and thick-skin areas (palms/soles) totally lack hair • hair on the scalp guards the head against physical trauma, heat loss, and sunlight • eyelashes shield the eyes • nose hairs filter large particles like lint and insects from inhaled air • hairs consist largely of flexible cells produced by hair follicles • as it grows, the older part of the hair is pushed upward, and its fused cells become increasingly keratinized and die

42. Hair • Composed of keratin • cross sectional shape of the shaft determines straight or curly hair type: • flat/ribbonlike shaft - hair is kinky • oval shaft - hair is smooth and silky (maybe wavy) • round shaft - hair is straight and tends to be coarse

43. Hair • classified as vellus or terminal • Vellus • body hair of children and adult females • pale, fine • terminal • coarser, often longer hair of the eyebrows and scalp • body hair of adult males • appear in the axillary and pubic regions at puberty of both sexes • influenced by nutrition, hormones, and conditions that increase local dermal blood flow

44. Hair • hair grows fastest from the teen years to the 40s - then growth slows (age-related atrophy) • leads to hair thinning and some degree of baldness • true (frank) baldness is male-pattern baldness and is genetically determined

46. 4. Nails • modification of epidermis that contains hard keratin • forms a clear protective covering on the dorsal surface of the distal part of a finger or toe • each nail has a free edge, a body (visible attached portion), and a proximal root (embedded in the skin) • lateral/proximal borders are overlapped by skin folds called nail folds (proximal nail fold is the cuticle) • white crescent over matrix is lunula

47. 4. Nails • deeper layers of the epidermis (stratum germinativum) extend beneath the nail as the nail bed • thickened proximal portion of the nail bed, called the nail matrix, is responsible for nail growth • pink color due to underlying capillaries • some melanin can be seen thru the nail if the skin color is dark

49. Skin Model Poster (up to 100) 3D model (bonus points) Include key with description of each structure

50. Question Box Closure • You asked…I found answers