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Chapter 4: The Tissue

Chapter 4: The Tissue . Level of Organization. There are 4 types of tissues – We will only study epithelial now. Epithelial Tissue. Covers exposed surfaces Example: The skin Lines internal passageways Example: The intestines Forms glands Example: Sweat glands. KEY CONCEPT.

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Chapter 4: The Tissue

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  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 • Cellularity (cell junctions) • Polarity (apical and basal surfaces) • Attachment (basal lamina) • Avascularity • Regeneration

  8. Functions of Epithelial Tissue • Provide physical protection • Control permeability a. Move fluids over the epithelium (protection) b. Move fluids through the epithelium (permeability) • Provide sensation • Produce specialized secretions (glandular epithelium) 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

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