1. Chapter 4: The Tissue Level of Organization

2. There are 4 types of tissues – We will only study epithelial now.

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

4. 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

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

6.  What are the special structures and functions of epithelial tissues?

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

8. 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)

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

10. Increasing Surface Area  Microvilli increase absorption or secretion  Cilia (ciliated epithelium) move fluids

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

12. Intercellular Connections  Support and communication

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

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

15. Tight Junctions  Between 2 cell membranes

16. Gap Junctions  Allow rapid communications

17. Desmosomes  CAMs, dense areas, and intercellular cement

18. Attachment to Basal Lamina  Hemidesmosomes

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

20. Classes of Epithelia  Based on shape and layers

21. Layers  Simple epithelium: –single layer of cells  Stratified epithelium: –several layers of cells

22. Cell Shape  Squamous epithelia: –Thin, flat, irregular shaped (fish scale)  Cuboidal epithelia: –square shaped (cube)  Columnar epithelia: –tall shaped (column)

23. Simple Squamous Epithelium

24. Stratified Squamous Epithelium

25. Cuboidal Epithelia  Simple cuboidal epithelium: Example – Kidney tubules –secretion and absorption

26. Cuboidal Epithelia  Stratified cuboidal epithelia: Sweat gland ducts –sweat and mammary ducts

27. Transitional Epithelium  Urinary bladder

28. Columnar Epithelia  Simple columnar epithelium: Intestinal Lining –absorption and secretion

29. Columnar Epithelia  Pseudostratified columnar epithelium: Trachea –cilia movement

30. Columnar Epithelia  Stratified columnar epithelium: Salivary Gland Duct –protection

31. Glandular Epithelia  Endocrine and exocrine glands

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

33. Exocrine Glands  Produce secretions: –onto epithelial surfaces –through ducts

34. Modes of Secretion – Exocrine Glands  Merocrine secretion

35. Modes of Secretion  Apocrine secretion

36. Modes of Secretion  Holocrine secretion

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

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

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

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

41. Structure of Multicellular Exocrine Glands