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Glandular Epithelial Tissues

Glandular Epithelial Tissues. A. General features & functions. Originate from lining epithelial cells that penetrate the C.T. and form secretory units Epithelial cells specialized to synthesize and secrete a specific product

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Glandular Epithelial Tissues

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  1. Glandular Epithelial Tissues

  2. A. General features & functions • Originate from lining epithelial cells that penetrate the C.T. and form secretory units • Epithelial cells specialized to synthesize and secrete a specific product • Classifications based on product distribution, structure, type of secretion, and mode of secretion

  3. Gland Formation

  4. B. Product distribution • Endocrine - lack ducts and secrete their products (hormones) into the C.T.

  5. Endocrine Glands Unicellular, e.g., enteroendocrine cells of the digestive tract. Small Clusters of Cells, e.g., islet of Langerhans in pancreas Organs, e.g., adrenal gland and pituitary

  6. Endocrine Glands • 1. Secretory cells of multicellular glands usually arranged as plates or cords. • 2. Highly vascular with fenestrated capillaries. • 3. Secretory products = hormones • a. Derivatized amino acids (thyroxine) • b. Peptides/proteins (insulin) • c. Steroids (estrogen) • 4. Merocrine or diffusion methods of product release only

  7. B. Product distribution • Exocrine - secrete their products onto surfaces via ducts • ducts formed by epithelial cells • ducts may simply convey or modify the secretion by adding to or concentrating it • individual gland cells show polarized distribution of organelles

  8. C. Structure of exocrine glands • Unicellular - secretory component consists of single cells

  9. Goblet Cells Mucin granules which contain highly glycosylated proteins which become hydrated when released and form mucus

  10. C. Structure of exocrine glands • Multicellular - > one cell, subclassified according to arrangement of parenchymal cells and ducts • sheet gland -simplest arrangement, all cells secretory • ducts - simple (unbranched) or compound (branched) • secretory unit of the gland: • tubular • acinar (alveolar) • tubuloacinar (tubuloalveolar)

  11. Sheet Gland

  12. Sheet Gland

  13. C. Structure of exocrine glands

  14. Simple Tubular Intestinal glands of the small and large intestine

  15. Simple, Branched Tubular Fundic glands of the stomach

  16. Simple, Coiled Tubular Sweat glands

  17. Simple, Branched Acinar Sebaceous and Meibomiumglands

  18. C. Structure of exocrine glands

  19. Compound Acinar

  20. Compound Tubuloacinar

  21. C. Structure of exocrine glands • Compound glands have a connective tissue capsule and septa that subdivide the gland into lobes and lobules • intralobular ducts - within a lobule • interlobular ducts - receive numerous intralobular ducts and exit from the lobule surrounded by FECT • interlobar ducts - receive interlobular ducts, in FECT between lobes – an excretory duct drains entire gland

  22. Duct Nomenclature InterlobularDuct

  23. Intercalated Intralobular Ducts

  24. Intralobular Ducts

  25. Interlobular Ducts

  26. Interlobar Duct

  27. 4. Special Features Myoepithelial Cells Serous Demilunes

  28. D. Type of secretion • Exocrine • mucous • serous • lipid • cerumen • Endocrine • polypeptide • steroid

  29. Exocrine - Mucus Secretion

  30. Mucus-Secreting Cells

  31. Mucous & Serous Secretions

  32. Serous-Secreting Gland

  33. Lipid-Secreting Gland

  34. Endocrine – Polypeptide Secretion

  35. Steroid-Secreting Cells

  36. E. Mode of secretion • Merocrine (eccrine) - product released by exocytosis • Apocrine - where part of the apical cytoplasm is released along with the secretory product • Holocrine - where the entire cell (may be dead or alive) and it's contents are released • Diffusion - product passes through plasmalemma, occurs in some endocrine gland cells only

  37. Merocrine (Eccrine) Secretion

  38. Apocrine Secretion

  39. Holocrine Secretion

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