The Integumentary System

1. The Integumentary System

2. Overview • Largest organ (15% of body weight) • 3 layers: • Epidermis • keratinized stratified squamous epithelium • Dermis • connective tissue layer • Hypodermis • Adipose & blood vessels

3. Structure of the Skin

4. Functions of the Skin • Resistance to trauma and infection (slightly acidic) • Barrier to UV light • Vitamin D synthesis • Sensory receptors • Thermoreceptors • Nonverbal communication

5. Cells of the Epidermis • Stem cells = undifferentiated cells • Keratinocytes = waterproofing • Melanocytes = make pigment that shields UV • Tactile (Merkel) cells = sense of touch • Dendritic (Langerhans) cells = fights pathogens

6. Cell and Layers of the Epidermis

7. Figure 6.2a

8. Stratum Basale • Single layer on basement membrane • Cell types in this layer • keratinocytes – divide to replace epidermis • melanocytes • Merkel cells

9. Stratum Spinosum Cell types: • keratinocytes • dendritic (Langerhans) cells

10. Stratum Granulosum • 3 to 5 layers Flat keratinocytes • Produces lipid-filled vesicles thatwaterproof the skin • forms a barrier between surface cellsand deeper layers • cuts off surface strata from nutrient supply, so top layers are dead

11. Stratum Lucidum • Thin translucent zone seen only in thick skin • Keratinocytes • Cells have no nucleus or organelles

12. Stratum Corneum • Up to 30 layers of dead, scaly,keratinized cells • surface cells flake off (exfoliate) – forms dust

13. Life History of Keratinocytes • Produced by stem cells in stratum basale • New cells push others toward surface • Cells filled with keratin • Cells die and exfoliate

14. Dermis • Thickness = 0.6mm to 3mm • Composition • collagen, elastic and reticular fibers, fibroblasts • Dermal papillae - extensions of the dermis into the epidermis • forming the ridges of the fingerprints • 2 Layers • papillary layer - top • reticular layer - bottom

15. Hypodermis • Subcutaneous • Mostly adipose • Functions • energy reservoir • thermal insulation • Hypodermic injections (subQ) • highly vascular

16. Skin Colors (Pigmentation) • Hemoglobin = red pigment of red blood cells • Carotene = yellow pigment • concentrates in stratum corneum and fat • Melanin = yellow, brown, and black hues • pigment synthesis stimulated by UV radiation

17. Abnormal Skin Colors 1 • Cyanosis = blueness from deficiency of oxygen in the blood (cold weather) • Erythema = redness due to dilated cutaneous vessels (anger, sunburn, embarrassment) • Jaundice = yellowing of skin and sclera due to excess of bilirubin in blood (liver disease)

18. Cyanosis

19. Erythema

20. Jaundice

21. Abnormal Skin Colors 2 • Bronzing = golden-brown color of Addison disease • Pallor = pale color from lack of blood flow • Albinism = a genetic lack of melanin • Hematoma = a bruise (visible clotted blood)

22. Addison’s Disease

23. Albinism

24. Albinism in animals

25. Hematoma

26. Skin Markings • Hemangiomas (birthmarks) • discolored skin caused by benign tumors of dermal blood capillaries (strawberry birthmarks disappear in childhood -- port wine birthmarks last for life) • Freckles and moles = group of melanocytes • freckles are flat; moles are elevated • Friction ridges leave oily fingerprints on touched surfaces • unique pattern formed during fetal development • Flexion creases form after birth by repeated closing of the hand • Flexion lines form in wrist and elbow areas

27. Characteristics of Human Hair • Hair (composed of hard keratin) • Hair found almost everywhere • differences between sexes or individuals is difference in texture and color of hair • 3 different body hair types • lanugo -- fine, unpigmented fetal hair • vellus -- fine, unpigmented hair of children and women • terminal hair -- coarse, long, pigmented hair of scalp

28. Structure of Hair and Follicle • Hair is filament of keratinized cells • shaft = above skin; root = within follicle • Follicle is oblique tube within the skin • bulb is where hair originates • vascular tissue (papilla) in bulb provides nutrients • Texture and shape of hair • straight hair = round; wavy = oval • Hair color = pigment in cells of cortex

29. Hair Color and Texture, Brunette Eumelanin pigment colors brown and black hair.

30. Hair Color and Texture, Blonde Blond hair contain pheomelanin pigment, but little eumelanin.

31. Hair Color and Texture, Red Red hair contains little eumelanin but lots of pheomelanin.

32. Hair Color and Texture, Gray and White White hair = air in medulla and lack of pigment in cortex. Gray hair is a mixture of white and pigmented hairs.

33. Structure of Hair Follicle • Epithelial root sheath • Connective tissue root sheath • Hair receptors entwine each follicle • Piloerector muscle • goose bumps

34. Hair Growth and Loss • Hair cycle = 3 repeating cycles • anagen is growth stage (90% of scalp follicles) • lasts 6-8 years in young adult • catagen is shrinking follicle (lasts 2-3 weeks) • telogen is resting stage (lasts 1-3 months) • Thinning or baldness = alopecia • Pattern baldness = genetic and hormonal • sex-influenced trait(dominant in males, recessive in females); expressed only with high testosterone levels • Hirsutism = excessive hair growth • hormone imbalance (ovary or adrenal cortex problem)

35. Functions of Hair • Body hair (too thin to provide warmth) • alert us to parasites crawling on skin • Scalp hair • heat retention and sunburn cover • Beard, pubic and axillary hair indicate sexual maturity and help distribute sexual scents • Guard hairs and eyelashes • prevent foreign objects from getting into nostrils, ear canals or eyes • Expression of emotions with eyebrows

36. Fingernail Structure

37. Nails • Derivative of stratum corneum • densely packed cells filled with hard keratin • Flat nails allow for fleshy, sensitive fingertips • Growth rate is 1 mm per week • new cells added by mitosis • nail plate is visible part of nail • medical diagnosis of iron deficiency = concave nails

38. Sweat (Sudoriferous) Glands • Purpose = cool us down • 500 ml of insensible perspiration/day • sweating with visible wetness = diaphoresis 2 types of sweat glands: • Eccrine – all over body • Apocrine glands – mainly axillary regions produce sweat containing fatty acids • found only near hair follicles and respond to stress and sex • bromhidrosis is body odor produced by bacterial action on fatty acids

39. Oil (Sebaceous) Glands • Sebaceous- oily secretion called sebum that contains broken-down cells • lanolin in skin creams is sheep sebum • opens into hair follicle

40. Ceruminous Glands • Found only in external ear canal • Their secretion combines with sebum to produce earwax • waterproof keeps eardrum flexible • bitterness repel mites and other pests

41. Mammary Glands • Develops in female breasts at puberty (male glands do not develop) • Function: produce milk after pregnancy • Additional nipples (polythelia)

42. Skin Cancer • Induced by UV rays of the sun • basal cell carcinoma (least dangerous) • arises from stratum basale and invades dermis • With surgery 99% survival rate • squamous cell carcinoma • arises from keratinocytes in stratum spinosum • metastasis to the lymph nodes can be lethal • malignant melanoma (most deadly) • arises from melanocytes of a preexisting mole

43. Figure 6.11a

44. Figure 6.11b

45. Figure 6.11c

46. ABCD Rule by American Cancer Society • A: A symmetry-the 2 sides of the pigmented spot or mole do not match • B: Border irregularity-borders of the lesion are not smooth, but exhibit indentations • C: Color- the pigmented spot contains several colors • D: Diameter-spot larger than 6 mm • (E: Elevation)

47. Burns • Hot water, sunlight, radiation, electric shock or acids and bases • Death from fluid loss and infection • Degrees of burns • 1st-degree = only the epidermis (red, painful and edema) • 2nd-degree = epidermis and part of dermis (blistered) • epidermis regenerates from hair follicles and sweat glands • 3rd-degree = epidermis, dermis and more is destroyed • often requires grafts or fibrosis and disfigurement may occur • Treatment – IV nutrition and fluid replacement, remove dead tissue, and infection control

48. Figure 6.12

49. Figure 6.12ab

50. Figure 6.12bb