The Integumentary System

1. 5 The Integumentary System

3. I. The Skin and the Hypodermis • A. skin - our largest organ • B. accounts for 7% of body weight • C. varies in thickness from 1.5 to 4.4mm • D. divided into two distinct layers • 1. epidermis • 2. dermis • a. hypodermis - lies deep to the dermis • b. composed of areolar and adipose tissues

4. Epidermis Dermis Hypodermis Deep fascia Muscle

5. Epidermis Papillarydermis Dermis Reticulardermis Hypodermis(superficial fascia)

7. II. Epidermis • A. is composed of keratinized stratified squamous epithelium • B. contains four main cell types: • 1. keratinocytes • Location—stratum spinosum; produce keratin, a fibrous protein • a. arise from deepest layer of epidermis • b. produce keratin, a tough fibrous protein • c. produce antibiotics and enzymes • d. keratinocytes are dead at skin’s surface

8. 2. melanocytes • Location—basal layer; manufacture and secrete pigment • 3. tactile epithelial cells • Location—basal layer; attached to sensory nerve endings • 4. dendritic cells • Location—stratum spinosum; macrophage-like

9. II. Layers of the Epidermis deep ► stratum basale (stratum geminativum) ► stratum spinosum ► stratum granulosum ► stratum lucidum (***only in thick skin***) surface ► stratum corneum

10. A. Stratum basale(at the “base”) • 1. deepest layer of epidermis • 2. attached to underlying dermis • 3. cells actively divide by mitosis • 4. contains: • a. tactile epithelial cells—associated with sensory nerve • b. melanocytes—secrete the pigment melanin

11. B. Stratum spinosum(“spiny” layer) • 1. “spiny” appearance • 2. contains thick bundles of intermediate filaments • 3. resist tension and contain the protein pre-keratin • 4. among the keratinocytes are star-shaped dendritic cells • a. are a type of macrophage • b. function in immune system

12. C. Stratum granulosum • 1. consists of a few layers of keratinocytes • a. keratinocytes contain: • ► keratohyaline granules—help form keratin • ► lamellar granules—contain waterproofing glycolipid • D. Stratum lucidum (“clear” layer) • 1. occurs only in thick skin • 2. locations of thick skin—palms and soles • 3. composed of a few rows of flat, dead keratinocytes

13. E. Stratum corneum(“horny” layer) • 1. only on thick layer of dead keratinocytes • 2. composed of a few rows of flat, dead keratinocytes • 3. protects skin against abrasion and penetration

14. Stratum corneum Most superficial layer; 20–30layers of dead cells representedonly by flat membranous sacsfilled with keratin. Glycolipids inextracellular space. Stratum granulosum One to five layers of flattenedcells, organelles deteriorating;cytoplasm full of lamellargranules (release lipids) andkeratohyaline granules. Stratum spinosum Several layers of keratinocytesunified by desmosomes. Cellscontain thick bundles ofintermediate filaments madeof pre-keratin. Desmosomes Stratum basale Deepest epidermal layer; one rowof actively mitotic stem cells;some newly formed cells becomepart of the more superficiallayers. See occasionalmelanocytes and dendritic cells. Dermis

15. Stratum corneum Keratinocytes Most superficial layer; 20–30layers of dead cells representedonly by flat membranous sacsfilled with keratin. Glycolipids inextracellular space. Stratum granulosum One to five layers of flattenedcells, organelles deteriorating;cytoplasm full of lamellargranules (release lipids) andkeratohyaline granules. Stratum spinosum Several layers of keratinocytesunified by desmosomes. Cellscontain thick bundles ofintermediate filaments madeof pre-keratin. Desmosomes Stratum basale Deepest epidermal layer; one rowof actively mitotic stem cells;some newly formed cells becomepart of the more superficiallayers. See occasionalmelanocytes and dendritic cells. Dermis Dendritic cell Sensorynerveending Melanocyte Melaningranule Tactileepithelial cell

17. III. Dermis • A. Second major region of the skin • B. Strong, flexible connective tissue • C. Richly supplied with blood vessels and nerves • D. Has two layers: • 1. Papillary dermis (layer)—includes dermal papillae • 2. Reticular dermis (layer) - deeper layer—80% of thickness

18. E. Papillary Dermis • 1. dermal papillae • a. more surface area ► exchange gases, nutrients, and wastes • b. lie on dermal ridges • 2. epidermal ridges (friction ridges) • a. elevations of dermal ridges • b. fingerprints - increase gripping ability of hands and feet

19. Hair shaft Dermal papillae Epidermis Papillarydermis Dermis Reticulardermis Hypodermis(superficial fascia) Adipose tissue

20. Openings ofsweat glandducts Friction ridges Flexure lineson digit Friction ridges offingertip (SEM 12) Flexure lineson the palm Flexure lines of the hand Cleavage lines in thereticular dermis

21. F. Reticular Dermis • 1. accounts for 80% of dermal thickness • 2. dense irregular connective tissue • 3. cleavage lines - separation between collagen fibers • 4. flexure lines - deep creases in palms and fingers • 5. important role in temperature regulation

22. Flexure lineson digit Flexure lineson the palm Flexure lines of the hand

23. G. Hypodermis - deep to the skin • 1. also called superficial fascia • 2. contains areolar and adipose connective tissue • 3. anchors skin to underlying structures • 4. helps insulate the body • 5. has different distribution in males and females

24. Hair shaft Epidermis Papillarydermis Dermis Reticulardermis Hypodermis(superficial fascia) Adipose tissue

25. IV. Skin Color • A. Two pigments contribute to skin color • 1. melanin - most important pigment—made from tyrosine • 2. carotene - yellowish pigment from carrots and tomatoes • 3. caucasian skin contains little melanin

26. V. Nails • A. Nails – scale-like modification of epidermis; hard keratin • 1. free edge • 2. body • 3. root • 4. nail folds • 5. eponychium (cuticle )

27. Lateral nail fold Lunule Free edgeof nail Nail plate Eponychium(cuticle)

28. Free edgeof nail Nail root Eponychium(cuticle) Nail matrix Nailplate Proximalnail fold Phalanx(bone of fingertip) Nail bed

29. B. Hair • 1. flexible strand of dead, keratinized cells • 2. hard keratin - tough and durable • 3. root - embedded in the skin • 4. shaft - projects above skin’s surface • a. hair has three concentric layers of keratinized cells • i. medulla - central core • ii. cortex - surrounds medulla • iii. cuticle - outermost layer • C. hair follicles - extend from epidermis into dermis

30. Hair shaft Epidermis Papillarydermis Dermis Reticulardermis Sebaceous (oil) gland Hair follicle Hair root Hypodermis(superficial fascia)

31. Hair shaft Arrector pili Sebaceousgland Follicle wall Peripheral connectivetissue (fibrous) sheath Hair root Glassy membrane Hair bulb Epithelial root sheath External root sheath Internal root sheath Hair Cuticle Cortex Medulla Diagram of a cross section of ahair within its follicle

32. Follicle wall Peripheral connectivetissue (fibrous) sheath Glassy membrane Epithelial root sheath External root sheath Internal root sheath Hair Cuticle Cortex Medulla Photomicrograph of a cross section of a hair and hair follicle (120)

33. Hair shaft Follicle wall Peripheral connective tissue (fibrous) sheath Glassy membrane Arrector pili Epithelial root sheath External root sheath Sebaceousgland Internal root sheath Hair root Hair root Cuticle Cortex Hair bulb Medulla Hair matrix Dermal papilla Melanocyte Subcutaneous adipose tissue Diagram of a longitudinal view of the expanded hairbulb of the follicle, which encloses the matrix

34. VI. Appendages of the Skin • A. wall of hair follicle • B. connective tissue root sheath • C. epithelial tissue root sheath • D. Arrectorpili muscle - bundle of smooth muscle • 1. hair stands erect when arrectorpili contracts

35. VII. Types and Growth of Hair • A. vellus hairs - body hairs of women and children • B. terminal hairs • 1. hair of scalp • 2. axillary and pubic area (at puberty) • 3. hair thinning and baldness due to aging • 4. male pattern baldness

36. VIII. Sebaceous Glands • A. occur over entire body (except palms and soles) • B. secrete sebum • 1. an oily substance • 2. Collects dirt • 3. softens and lubricates hair and skin • C. simple alveolar glands • D. most are associated with a hair follicle • 1. holocrine secretion - entire cell breaks up to form secretion

37. IX. Sweat Glands • A. (sudoriferous glands) - widely distributed on body • B. sweat - is a blood filtrate • 1. 99% water with some salts • 2. Contains traces of metabolic wastes • 3. about 2% urea

38. C. Two types of sweat gland • 1. eccrine gland (merocrine) - produce true sweat • 2. apocrine gland • a. confined to axillary, anal, and genital areas • b. produce a special kind of sweat • c. musky odor—attracts a mate • d. ceruminous glands (ear wax) and mammary glands

39. Epidermis Papillarydermis Sweat pore Appendages of skin Dermis Eccrine sweat gland Reticulardermis Arrectorpili muscle Sebaceous (oil) gland Hair follicle Hair root Hypodermis(superficial fascia) Adipose tissue

40. X. Burns • A. classified by severity • 1. first-degree burn - only upper epidermis is damaged • 2. second-degree burn - upper part of dermis is also damaged • a. blisters appear • b. skin heals with little scarring • 3. third-degree burn • a. consumes thickness of skin • b. burned area appears white, red, or blackened • B. The Rule of Nines

41. Totals Anterior values 4½% 1st degree burn Anterior and posteriorhead and neck, 9% Anterior and posteriorupper limbs, 18% 2nd degree burn 4½% 4½% Anterior and posteriortrunk, 36% Anteriortrunk, 18% Skin bearing partial-thickness burn(first- and second-degree burn) 3rd degree burn 9% 9% (Perineum, 1%) Anterior and posteriorlower limbs, 36% 100% Skin bearing full-thickness burn(third-degree burn) Rule of nines; used to estimateextent of burns

42. XI. Skin Cancer A. basal cell carcinoma - least malignant and most common B. squamous cell carcinoma - arises from keratinocytes C. melanoma - A cancer of melanocytes; most dangerous type

43. Basal cell carcinoma Squamous cell carcinoma Melanoma