1. The Integument Chapter 5 http://www.udel.edu/biology/Wags/histopage/colorpage/cin/cinshf.GIF

2. Skin (Integument) Consists of three major regions 1.Epidermis—superficial region 2.Dermis—middle region Hypodermis (superficial fascia)—deepest region Subcutaneous layer deep to skin (not technically part of skin) Mostly adipose tissue

3. Copyright © 2010 Pearson Education, Inc. Figure 5.1 Epidermis Hair shaft Dermis Reticular layer Papillary layer Hypodermis (superficial fascia) Dermal papillae Pore Subpapillary vascular plexus Appendages of skin Eccrine sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Nervous structures Sensory nerve fiber Pacinian corpuscle Hair follicle receptor (root hair plexus) Cutaneous vascular plexus Adipose tissue

4. Epidermis Keratinized stratified squamous epithelium Cells of epidermis – Keratinocytes – Melanocytes – Epidermal dendritic (Langerhans) cells – Tactile (Merkel) cells http://www.technion.ac.il/~mdcourse/274203/slides/Ski n/6-Langerhans%20Cells.jpg

5. Layers of the Epidermis: Stratum Basale (Basal Layer) Deepest epidermal layer firmly attached to the dermis Single row of stem cells Also called stratum germinativum: cells undergo rapid division Journey from basal layer to surface – Takes 25–45 days

6. Layers of the Epidermis: Stratum Spinosum (Prickly Layer) Cells contain a weblike system of intermediate prekeratin filaments attached to desmosomes Abundant melanin granules and dendritic cells

7. Layers of the Epidermis: Stratum Granulosum (Granular Layer) Thin; three to five cell layers in which the cells flatten Keratohyaline and lamellated granules accumulate

8. Layers of the Epidermis: Stratum Lucidum (Clear Layer) Only in thick skin Thin, transparent band superficial to the stratum granulosum A few rows of flat, dead keratinocytes http://legacy.owensboro.kctcs.edu/gcaplan/anat/notes/161_epidermis.gif

9. Layers of the Epidermis: Stratum Corneum (Horny Layer) 20–30 rows of dead, flat, keratinized membranous sacs Three-quarters of the epidermal thickness Functions – Protects from abrasion and penetration – Waterproofs – Barrier against biological, chemical, and physical assaults

10. Dermis Strong, flexible connective tissue Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells Two layers: – Papillary – Reticular

11. Copyright © 2010 Pearson Education, Inc. Figure 5.1 Epidermis Hair shaft Dermis Reticular layer Papillary layer Hypodermis (superficial fascia) Dermal papillae Pore Subpapillary vascular plexus Appendages of skin Eccrine sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Nervous structures Sensory nerve fiber Pacinian corpuscle Hair follicle receptor (root hair plexus) Cutaneous vascular plexus Adipose tissue

12. Layers of the Dermis Papillary layer – Areolar connective tissue with collagen and elastic fibers and blood vessels – Dermal papillae Reticular layer – ~80% of the thickness of dermis – Collagen and elastic fibers (dense irregular connective tissue)

13. Layers of the Dermis Papillary Reticular Epidermis Dermis

14. Skin Markings Friction Ridges – Increase gripping ability of fingers and feet Cleavage Lines – Separations b/w less dense areas of collagen fibers – Incisions made parallel to cleavage lines heal more readily

15. Skin Color Three pigments contribute to skin color: 1.Melanin Yellow to reddish-brown to black, responsible for dark skin colors 2.Carotene Yellow to orange, most obvious in the palms and soles 3.Hemoglobin Responsible for the pinkish hue of skin

16. Appendages of the Skin Derivatives of the epidermis – Sweat glands – Oil glands – Hairs and hair follicles – Nails

17. Sweat Glands Two main types of sweat glands 1.Eccrine sweat glands abundant on palms, soles, and forehead 2.Apocrine sweat glands confined to axillary and anogenital areas Ceriminous glands – earwax Mammary glands – secret milk

18. Copyright © 2010 Pearson Education, Inc. Figure 5.5b (b) Photomicrograph of a sectioned eccrine gland (220x) Secretory cells Dermal connective tissue Duct Sebaceous gland Sweat pore Eccrine gland

19. Sebaceous (Oil) Glands Widely distributed Most develop from hair follicles Become active at puberty Secrete Sebum

20. Hair Functions – Alerting the body to presence of insects on the skin – Guarding the scalp against physical trauma, heat loss, and sunlight Distribution – Entire surface except palms, soles, lips, nipples, and portions of external genitalia Consists of dead keratinized cells Hair pigments: melanins (yellow, rust brown, black)

21. Copyright © 2010 Pearson Education, Inc. Figure 5.6a Hair shaft Arrector pili Sebaceous gland Hair root Hair bulb (a) Diagram of a cross section of a hair within its follicle Connective tissue root sheath Glassy membrane External epithelial root sheath Internal epithelial root sheath Follicle wall Cuticle Cortex Medulla Hair

22. Hair Follicle Extends from the epidermal surface into dermis Two-layered wall: outer connective tissue root sheath (dermis), inner epithelial root sheath (epidermis) Hair bulb: expanded deep end Hair follicle receptor (root hair plexus) – Sensory nerve endings around each hair bulb Stimulated by bending a hair Arrector pili – Smooth muscle attached to follicle – Responsible for “ goose bumps ”

23. Figure 5.6c Hair shaft Arrector pili Sebaceous gland Hair root Hair bulb Photomicrograph of longitudinal view of the hair bulb of the follicle (160  ) Internal epithelial root sheath External epithelial root sheath Connective tissue root sheath Follicle wall Hair matrix Hair papilla Subcutaneous adipose tissue Medulla Cortex Cuticle Glassy membrane Hair root

24. Hair Types – Vellus—pale, fine body hair of children and adult females – Terminal—coarse, long hair of eyebrows, scalp, axillary, and pubic regions (and face and neck of males) Thinning/Baldness – Alopecia – True (frank) baldness http://thebeautybrains.com/wp- content/uploads/2007/08/baby-hair.jpg

25. Structure of a Nail Scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes

26. Functions of the Integumentary System 1.Protection—three types of barriers – Chemical, physical/mechanical, biological 2.Body temperature regulation 3.Cutaneous sensations 4.Metabolic functions 5.Blood reservoir 6.Excretion

27. Skin Cancer Risk factors – Overexposure to UV radiation – Frequent irritation of the skin Three major types: – Basal cell carcinoma – Squamous cell carcinoma – Melanoma

28. Burns Heat, electricity, radiation, certain chemicals Immediate threat: – Dehydration and electrolyte imbalance, leading to renal shutdown and circulatory shock Rule of Nines

29. Burns Partial Thickness – First degree Epidermal damage only – Second degree Epidermal and upper dermal damage Full Thickness – Third Degree Entire thickness of skin

30. Developmental Aspects: Old Age Epidermal replacement slows Subcutaneous fat and elasticity decrease Increased risk of cancer http://1.bp.blogspot.com/- f_6MgLAfZb4/T2mjLJxVr7I/AAAAAAAAAYc/DcoYDZHP8HM/s1600/old- age-bebo-dot-com.jpg