Chapter 5, part 1

1. Chapter 5, part 1 The Tissue Level of Organization--Integument

2. Learning Objectives • List the components of the integumentary system, including their physical relationships. • Specify the functions of the integumentary system. • Describe the main features and functions of the epidermis and dermis. • Discuss individual and racial differences in skin. • Discuss the effects of UV light on the epidermis. • Explain the structure and function of the various accessory organs of the skin. • Explain how the skin responds to injury and aging.

3. SECTION 5-1The Integumentary System: An Overview

4. The integumentary system consists of • Cutaneous membrane • Epidermis • Dermis • Accessory structures • Subcutaneous layer

5. Integumentary system functions: • Protection • Excretion • Temperature maintenance • Nutrient storage • Vitamin D3 synthesis • Sensory detection

6. Figure 5.1 The Components of the Integumentary System Figure 5.1

7. SECTION 5-2The Epidermis

8. Figure 5.2 Thin Skin and Thick Skin • The epidermis is composed of layers of keratinocytes • Thin skin = four layers (strata) • Thick skin = five layers Figure 5.2

9. The epidermis • Provides mechanical protection • Prevents fluid loss • Keeps microorganisms from invading the body

10. Layers of the epidermis: • Stratum germinativum • Stratum spinosum • Stratum granulosum • Stratum lucidum • Stratum corneum

11. Figure 5.3 The Epidermal Ridges of Thick Skin Figure 5.3

12. Epidermal characteristics: • Cells accumulate keratin and eventually are shed • Epidermal ridges are interlocked with dermal papillae • Fingerprints • Improve gripping ability • Langerhans cells (immunity) in s. spinosum • Merkel cells (sensitivity) in s. germinativum

13. Figure 5.4 The Structure of the Epidermis Figure 5.4

14. Skin color depends on • Blood supply • Carotene and melanin • Melanocytes produce melanin and protect from UV radiation • Epidermal pigmentation • Interrupted blood supply leads to cyanosis

15. Figure 5.5 Melanocytes Figure 5.5a, b

16. Epidermal cells • Synthesize vitamin D3 (cholecalciferol) when exposed to UV • Respond to epidermal growth factor • Growth • Division • Repair • Secretion

17. SECTION 5-3The Dermis

18. Dermal Organization • Papillary layer • Contains blood vessels, lymphatics, sensory nerves of epidermis • Reticular layer • Contains network of collagen and elastic fibers to resist tension

19. Figure 5.8 Dermal Circulation Figure 5.8

20. Stretch marks • Caused by excessive stretching of the dermis • Patterns of collagen and elastic fibers form lines of cleavage

21. Figure 5.7 Lines of Cleavage of the Skin Figure 5.7

22. Dermal Circulation and innervation • Cutaneous plexus arteries found in subcutaneous layer/ papillary dermis • Cutaneous sensory receptors (light touch, pressure)