1. Chapter 4: Tissues

2. Epithelial Tissue  Covers exposed surfaces –Example: The skin  Lines internal passageways –Example: The intestines  Forms glands –Example: Sweat glands

3. KEY CONCEPT  Tissues are collections of cells and cell products that perform specific, limited functions  4 tissue types form all the structures of the human body: –epithelial, connective, muscle, and neural

4. Epithelial Tissues  Epithelia: –layers of cells covering internal or external surfaces  Glands: –structures that produce secretions

5. Characteristics of Epithelia 1.Cellularity (cell junctions) 2.Polarity (apical and basal surfaces) 3.Attachment (basal lamina) 4.Avascularity 5.Regeneration

6. Functions of Epithelial Tissue 1.Provide physical protection 2.Control permeability a. Move fluids over the epithelium (protection) a. Move fluids over the epithelium (protection) b. Move fluids through the epithelium (permeability) b. Move fluids through the epithelium (permeability) 3.Provide sensation 4.Produce specialized secretions (glandular epithelium) a. Produce secretions (protection and messengers) a. Produce secretions (protection and messengers)

7. Free Surface and Attached Surface  Polarity: –apical and basolateral surfaces

8. Increasing Surface Area  Microvilli increase absorption or secretion -respiratory tract, digestive tract  Cilia (ciliated epithelium) move fluids -injury to cilia – smoking, abrasion

9. Effective Barriers  Physical integrity is maintained by: –intercellular connections –attachment to basal lamina –maintenance and repair

10. Intercellular Connections  Support and communication

11. Large Connections  CAMs (cell adhesion molecules): –transmembrane proteins  Intercellular cement

12. Cell Junctions  Form bonds with other cells or extracellular material: –tight junctions –gap junctions –desmosomes

13. Tight Junctions  Between 2 cell membranes  Prevents passage of water and solutes

14. Gap Junctions  Allow rapid communications  Allows ions and small molecules to pass through  Held together by channel proteins

15. Desmosomes  CAMs, dense areas, and intercellular cement  Ties cells together, helps to stabilize cell shape

16. Attachment to Basal Lamina  Hemidesmosomes – half of a desmosome, attaches cell to basal lamina

17. Repairing and Replacing Epithelia  Epithelia are replaced by division of germinative cells (stem cells) –Continuous  Near basal lamina

18. Glandular Epithelia  Endocrine and exocrine glands

19. Endocrine Glands  Release hormones: –into interstitial fluid –no ducts

20. Exocrine Glands  Produce secretions: –onto epithelial surfaces –through ducts –Tears, milk, enzymes into digestive tract, perspiration on skin

21. Modes of Secretion – Exocrine Glands  Merocrine secretion – produced in Golgi apparatus, released by vesicles (exocytosis)

22. Modes of Secretion  Apocrine secretion – produced by Golgi apparatus, released by shedding cytoplasm

23. Modes of Secretion  Holocrine secretion – released by cells bursting

24. Types of Secretions – Exocrine Glands  Serous glands: –watery secretions  Mucous glands: –secrete mucins  Mixed exocrine glands: –both serous and mucous

25. Gland Structure – Exocrine Glands  Exocrine glands can be classified as: –unicellular glands –multicellular glands

26. Unicellular Glands  Goblet cells are the only unicellular exocrine glands: –scattered among epithelia –e.g., in intestinal lining

27. Structure of Multicellular Exocrine Glands  Structural classes of exocrine glands

28. Structure of Multicellular Exocrine Glands