Integument

1. Integument Ms. Hughes Bio II

2. Integumentary System (Skin) • the skin has a surface area of 1.5 to 2 square meters, weighs 9 to 11 pounds (7% of total body weight in the average adult), and varies in thickness from 1.5 mm – 4 mm • 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

3. Skin Cell

4. protects the body from • mechanical damage (bumps and cuts) • chemical damage (acids, bases, poisons) • thermal damage (heat and cold) • UV radiation (sunlight) • invasion (bacterial)

5. capillary network and sweat glands regulate heat loss • mini-excretory system (skin loses urea, salts, and water during sweating) • manufactures several proteins important in immunity • synthesizes vitamin D from sunlight and cholesterol • contains sensory receptors for touch, pressure, temperature, and pain • two distinct regions • epidermis and dermis • usually firmly connected but friction/burns may cause them to separate and form a blister

6. Epidermis • avascular • thick to prevent water loss • different types of cells

7. keratinocytes • produce keratin • protective properties • arise in the deepest part of the epidermis • undergo almost continuous mitosis • reach free surface of skin, they are dead, scalelike structures • (keratin-filled plasma membranes) • millions of these dead cells rub off every day • (we have a totally new epidermis every 35 to 45 days)

8. Melanocytes • specialized epithelial cells that synthesize the pigment melanin  • touch all the keratinocytes • melanin granules accumulate on superficial, or "sunny," side of keratinocyte nucleus • forms a pigment shield to protect the nucleus from the damaging effects of UV radiation • same relative number of melanocytes • skin color due to differences in melanocyte activity  • freckles/moles are where melanin is concentrated in one spot

9. five distinct layers (deep to superficial):

10. Basal layer aka stratum germinativum (“growing layer”) • 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 • alternate name, stratum basale (“bottom layer”) • 10% to 25% melanocytes

11. stratum spinosum (“prickly layer”)  • weblike system of intermediate filaments • tension-resisting bundles of keratin filaments • keratinocytes in this layer are somewhat flattened and irregular in shape

12. stratum granulosum (“granular layer”)  • three to five cell layers • nuclei/organelles begin to disintegrate which makes keratinocytes flat granules of keratin accumulate which helps in slowing water loss • superficial to this layer epidermal cells are too far from dermal capillaries • adequate nourishment is not received and they die

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

14. stratum corneum (“horny layer”)  • 20 to 30 cell layers thick • accounts for up to three-quarters of the epidermal thickness • keratin and thickened plasma membranes protect the skin against abrasion and penetration • glycolipids between cells waterproofs this layer • cornified/horny cells shed from the scalp and flakes slough off dry skin • average person sheds 40 pounds of these skin flakes in a lifetime

15. 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

16. Papillary Layer • fibers form a loosely woven mat heavily invested with blood vessels • superior surface has nipple-like projections called dermal papillae • contain capillary loops, nerve endings (pain receptors), and touch receptors • larger mounds called dermal ridges produce looped/whorled ridges on the epidermal surface • epidermal ridges increase friction and enhance the gripping ability of the fingers and feet • lots of sweat pores on ridges that leave unique patterns (fingerprints)

17. Reticular Layer • deeper layer containing sweat glands, oil glands, and blood vessels (80% of the dermis) • has deep pressure receptors and lots of phagocytes • has collagen fibers (toughness and attracts water to help the skin stay hydrated) and elastin fibers • (provides elasticity) - both are lost with age

18. Subcutaneous Tissue • deep to the dermis • known as the hypodermis or superficial fascia • anchors the skin to underlying organs • shock absorber and insulator for the deeper tissues

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

20. Pigments

21. 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

22. 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

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

24. sweat (sudoriferous) glands  • formed by stratum germinativum and pushed deep into the dermis • entire skin surface except the nipples and parts of the external genitalia • 2.5 million per person

25. eccrine glands • more numerous • abundant on the palms, soles of the feet, and forehead • duct extends to open in a funnel-shaped pore • secretion is commonly called sweat • 99% water, with some salts, vitamin C, antibodies, traces of metabolic wastes, lactic acid, and small amounts of ingested drugs

26. pH between 4 and 6 • major role is to prevent overheating of the body • heat-induced sweating begins on the forehead and then spreads over the rest of the body • emotionally induced sweating (cold sweat brought on by fright, embarrassment, or nervousness) begins on the palms, soles, and armpits and then spreads to other body areas

27. 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 • viscous with a milky or yellowish color • secretion is odorless • bacteria on skin use fat/proteins for nutrients and cause it to develop the musky body odor • begin to function at puberty • little role to play in thermoregulation

28. 2 other 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

29. 3. 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 • important bactericide

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

31. 4. hair follicles/hair •  follicles extend from the epidermal surface into the dermis (hypodermis in the scalp) • deep end of the follicle is expanded, forming a hair bulb with sensory nerve endings (root hair plexus) • papilla (nipple-like bit of tissue) containing a knot of capillaries, protrudes into the hair bulb • wall thins as it approaches the hair bulb so that only a single layer of stratum germinativum cells covers the papilla to supply nutrients to the growing hair • the growth zone (matrix) in the hair bulb includes cells that actively divide to produce hair • (often triggered by chemical signals)

32. 4. hair follicles/hair • associated with each hair follicle is a bundle of smooth muscle cells called an arrectorpili • contraction pulls the hair follicle into an upright position & dimples the skin surface (goose bumps) • bending the hair can also stimulate nerves (sensing an insect crawling over your skin) • millions of hairs are scattered over nearly all of the body • about 100,000 of them in the scalp (lose an average of 90 scalp hairs daily) • 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

33. 4. hair follicles/hair • hair pigment is made by melanocytes at the base of the hair follicle • gray or white hair results from decreased melanin production • 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

34. 4. hair follicles/hair • hard keratin is tougher, more durable, and individual cells do not flake off • chief regions of a hair are the shaft (projects from skin), and the root (embedded in the skin) • 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

35. 4. hair follicles/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

36. 4. hair follicles/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 • much less dramatic in women • coarse terminal hairs are replaced by vellus hairs • true (frank) baldness is male-pattern baldness and is genetically determined • delayed-action gene switches on in adulthood and changes the response to testosterone • follicular growth cycles become short (many hairs never emerge from follicles before shedding)

37. 5. Nails • scalelike modification of the 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) • 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 • white crescent over matrix is lunula

40. Homeostatic Imbalances of the Skin • the skin can have more than 1000 different disorders (allergies, bacterial, viral, fungal, burns, cancers) • athlete’s foot (tineapedis) • red, peeling skin between or underneath the toes (usually but not always itchy)  • cold sores • herpes virus that localizes in a mucosal cutaneous nerve as a small blister that itches and stings • remains dormant until activated by emotional upset, fever, or UV radiation • contact dermatitis • itching, redness, and swelling of the skin due to chemical irritants • burns • tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals • body loses fluids through seepage from wound leading to dehydration • dehydration leads to renal failure and circulatory shock • volume of fluid loss can be estimated by the “rule of nines”

41. Athletes foot

42. Cold sore

43. Contact dermatitis

44. Burns

45. the body is divided into 11 areas each representing 9% plus 1% for the perineum

46. burned skin is sterile for 24 hours before bacteria/fungi begin invading thru damaged areas • 1st degree burns – only the epidermis is damaged, redness/swelling occur, regeneration • 2nd degree burns – epidermis/upper dermis is damaged, blisters develop, regeneration • 3rd degree burns – destroys entire thickness of skin, burned areas appear white/black, no regeneration

47. Skin Cancer • single most common type of cancer • cause of most are unknown but the most important risk factor is UV exposure • most are benign and do not spread (warts) • some are malignant

48. basal cell carcinoma • least malignant, most common, slow growing • stratum germinativum does not form keratin and spread into the dermis • easily removed with high recovery rate • squamous cell carcinoma • appears red and scaly, rapid growth • starts in stratum spinosum on scalp, ears, dorsal hand • chance for complete recovery if caught early

49. malignant melanoma • cancer of the melanocytes • begins as spontaneous cancer in pigmented areas (often from pigmented moles) • metastasizes rapidly into surrounding lymph/blood vessels • often fatal

50. Skin Cancer