The Integumentary System

1. Chapter 6 The Integumentary System

2. Introduction • Skin • Large waterproof covering • UV light and chemical protection • Accessory structures • Hair, nails, glands

3. The Layers of the Skin

4. Introduction • Epidermis: upper layer • Epithelial tissue divided into sublayers • Dermis: lower layer • Dense connective tissue • Connects skin to fat and muscle • Below dermis is subcutaneous layer called hypodermis

5. Introduction (cont’d.)

6. The Epidermis • Stratified, squamous, keratinized, epithelium • Keratinization • Cells move to surface, lose water and nuclei change • Composed of five layers

7. The Epidermis (cont’d.) • Stratum corneum • Outermost layer • Dead, keratinized cells • Barrier to light, heat, chemicals, microorganisms

8. The Epidermis (cont’d.) • Stratum lucidum • One to two cell layers thick • Flat and transparent • Difficult to see

9. The Epidermis (cont’d.) • Stratum granulosum • Two or three layers • Flattened cells • Active keratinization • Lose nuclei • Compact and brittle

10. The Epidermis (cont’d.) • Stratum spinosum • Several layers of spiny-shaped cells • Desmosomes prevalent • Desmosomes: interlocking cellular bridges

11. The Epidermis (cont’d.) • Stratum germinativum • Rests on basement membrane • Lowermost layer called stratum basale • New cells produced here (mitosis) • Melanocytes: produce melanin • Skin color • Albinism

12. The Dermis • Also called corium • Structures found in dermis • Blood and lymph vessels • Nerves • Muscles • Glands • Hair follicles

13. The Dermis (cont’d.) • Divisions • Papillary • Adjacent to the epidermis • Reticular • Between papillary and subcutaneous • Subcutaneous (hypodermis) • Layers of fat below the dermis

14. The Accessory Structures of the Skin

15. Hair • Covers most of the surface of the body • Three parts: cuticle, cortex, medulla • Shaft: visible portion • Root: hair follicle • Arrector pili: smooth muscle

16. Hair (cont’d.) • Growth • Hair follicle • Cycles of growth and rest • Texture: straight, curly, or tightly curly • Color: based on complex genetic factors

17. Nails • Modified epidermal cells • Lunula: white crescent • Body: visible portion • Root: covered by skin • Growth occurs from the nailbed

18. Nails (cont’d.)

19. Sebaceous Glands • Produce sebum (oil) • Lubricates skin and hair • Secretion controlled by endocrine system • Increases at puberty • Decreases in later life

20. Sweat Glands • Most numerous in palms and soles • Not found on margins of the lips or head of the penis • Each gland has secretory portion and excretory duct • Sweating helps cool the body

21. Functions of the Integumentary System

22. Sensation • Temperature receptors • Hot and cold • Pressure receptors • Excessive pressure as pain • Mild pressure as pleasurable • Combinations produce burning, itching, tickling

23. Protection • Prevents passage of harmful physical and chemical agents • Melanin protects from UV rays • Lipid content inhibits water loss • Acid mantle: kills most bacteria • Nails protect ends of our digits • Hair acts as insulation and filter

24. Thermoregulation • Normal body temperature: 98.6 degrees F • When external temperatures increase • Blood vessels dilate • Sweat occurs • When external temperatures decrease • Blood vessels first dilate then constrict

25. Secretion • Sebum • Cosmetic gloss • Moisturizer • Antifungal/antibacterial properties • Sweat • Essential in cooling process • Vitamin D

26. Animation – The Skin • Watch the Skin animation and see the structures of the skin up close. Click Here to Play Skin Animation

27. Animation – Tissue Repair • Watch the Tissue Repair animation to understand how the skin heals and a scar is formed after a deep laceration. Click Here to Play Tissue Repair Animation

28. Summary • Discussed the layers of the epidermis and the process of keratinization • Described the structure of the dermis • Discussed the accessory structures of the skin including the hair and nails • Discussed the different functions of the integumentary system