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. 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 Apical Lateral Lumen Basal

4. The Apical Region Epithelial Specializations: MicrovilliStereocilia Cilia small intestinesepididymis fallopian tube

5. 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 Microvilli terminal web microvillus border Small intestines

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

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

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

9. 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 The Junctional Complex

10. Electron micrographs of the junctional complex

11. The Basal Region Basement membrane 1.Basal Lamina Secreted by epithelial cells Barrier between epithelium and connective tissue Collagen type IV, proteogylcans & glycoproteins (PAS +) 2.Reticular Lamina Connective tissue below epithelium Collagen type III Hemidesmosomes Junctions that anchors epithelial cells to basal lamina basal lamina PAS stain

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? a)type II b)type III c)type IV d)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 What type of stratified epithelium is seen above? Stratified Squamous 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

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 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: Figure A Figure B Lab 3, Slide 35 Lab 3, Slide 25

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