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SSN Session

SSN Session. Epithelial Tissue Jennifer Chang (jtc2109) Bram Welch-Horan (tbw5) October 11, 2005. Epithelium. What is epithelium? Covers exterior surfaces Lines internal closed cavities and body tubes Forms secretory portions of ducts and glands Avascular tissue

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SSN Session

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  1. SSN Session Epithelial Tissue Jennifer Chang (jtc2109) Bram Welch-Horan (tbw5) October 11, 2005

  2. Epithelium • What is epithelium? • Covers exterior surfaces • Lines internal closed cavities and body tubes • Forms secretory portions of ducts and glands • Avascular tissue • High regeneration capacity

  3. Lumen Apical Lateral Basal Polarized Cells • Apical: • faces the lumen or outside world • separated from the basolateral side by tight junctions • Basolateral: • Lateral: • side that faces neighboring cell • forms functional continuum with basal side • Basal: • adheres to extracellular connective tissue – basement membrane

  4. The Apical Region Epithelial Specializations: Microvilli Stereocilia Cilia fallopian tube small intestines epididymis

  5. Microvilli • Cytoplasmic processes that extend from cell surfaces • Made of actin skeleton above intermediate filaments • Increase area for absorption as in small intestine • Insert into terminal web microvillus border terminal web Small intestines

  6. Stereocilia • Long microvilli (NOT CILIA!) • Non-motile Epididymis

  7. Cilia • Motile processes of microtubules that move synchronously • Insert into basal bodies (1 cilium per 1 body) • 9+2 microtubule arrangement Basal bodies cilia Fallopian tube Trachea

  8. microvillus border terminal bar terminal bar terminal web The Lateral Region Junctional Complex (aka Terminal Bar) : site of specialized attachment of adjoining epithelial cells Bodian silver stain

  9. The Junctional Complex • 3 Components (apical -> basal): • 1. Zonula Occludens=Tight Junction • most apical • located around entire perimeter • diffusion barrier • 2. Zonula Adherens • around entire perimeter • add to integrity of epithelial surface • 3. Macula Adherens=Desmosome • occur at small discrete sites • Gap junctions • at small discrete sites • metabolic and electrical coupling

  10. Electron micrographs of the junctional complex

  11. The Basal Region • Basement membrane • Basal Lamina • Secreted by epithelial cells • Barrier between epithelium and connective tissue • Collagen type IV, proteogylcans & glycoproteins (PAS +) • Reticular Lamina • Connective tissue below epithelium • Collagen type III • Hemidesmosomes • Junctions that anchors epithelial cells to basal lamina PAS stain basal lamina

  12. Question 1. This structure is typically found in the a) trachea b) kidney c) epididymis d) small intestines

  13. Question 2. Which of the following is FALSE regarding the structure at the pointer? a) its permeability determines whether the epithelia is “tight or “leaky” b) it occurs at small discrete sites c) it separates the apical surface from the basolateral surface d) it is a component of the junctional complex

  14. Question 3 What type of collagen is found in the tissue at the pointer? type II type III type IV type VII

  15. Types of Epithelial Cells

  16. Epithelial Cell Types - Nomenclature • Simple – 1 cell layer thick • Stratified – 2 or more cell layers thick • Squamous – cell width > height (i.e., flat) • Cuboidal – width/depth/height ~same • Columnar – cell height >> width

  17. Simple Squamous Epithelium • 1 cell layer thick • function: exchange • absorption, secretion, diffusion • e.g. – blood vessels • barrier function in CNS

  18. Simple Cuboidal • cuboidal shape (or pyramidal) • round, central nucleus • absorption / secretion, conduit • e.g. – small ducts of exocrine glands • (pancreas), kidney tubules

  19. Simple Columnar • elongated cells w/ • elongated nuclei • height > width • absorptive • (e.g. small intestine) • or secretory • (e.g. gastric glands) • other examples: • -lining of colon, • stomach, gall bladder

  20. Stratified Epithelium • 2 or more layers thick • classified based on • surface cells • (can be squamous, • cuboidal, or columnar) • functions include: • protection, barrier, • resist abrasion • Examples: epidermis, • esophagus, larger • exocrine ducts What type of stratified epithelium is seen above?

  21. Stratified Epithelium • 2 or more layers thick • classified based on • surface cells • (can be squamous, • cuboidal, or columnar) • functions include: • protection, barrier, • resist abrasion • Examples: epidermis, • esophagus, larger • exocrine ducts What type of stratified epithelium is seen above? Stratified Squamous Epithelium

  22. Pseudostratified Epithelium • All cells rest on basement membrane, but not all reach apical surface • function: secretion, absorption, conduit • e.g., trachea, epididymis

  23. Transitional Epithelium

  24. Transitional Epithelium – “Urothelium" • special stratified epithelium • apical surface may appear “domed” • (empty) and flattened full) • function: distensibility • lines lower urinary tract • i.e., ureters, bladder, proximal urethra

  25. Question 4 What kind of epithelium lines the secretory alveoli of this exocrine gland? a. Simple Columnar b. Simple Cuboidal c. Squamous d. Transitional

  26. Questions 5, 6 Figure A Figure B Lab 3, Slide 25 Lab 3, Slide 35 • 5. Select the one correct statement regarding the surface epithelium. • 6. The tissue or tissues that are specialized to provide a barrier to luminal absorption are shown in:

  27. Question 7 This epithelial cell type is found in: a. Bladder b. Kidney tubules c. Intestinal epithelium d. Epidermis

  28. Question 8 What type of epithelium is this? a. Pseudostratified b. Stratified Columnar c. Stratified Squamous d. Stratified Cuboidal

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