1. Epithelium, Glands and Intercellular Junctions

2. What is an epithelium? Epithelia line lumens and cover surfaces Epithelia are usually non-vascularized Epithelial cells are polarized, having basal and apical aspects; they are often intimately associated with connective tissue below Epithelia may have innervation and lymphoid (immune system) elements Epithelia usually have a high rate of cell turnover, and are most susceptible to disturbances in mitosis (i.e., tumor formation) Epithelia are capable of adaptive metaplasia, a reversible condition

3. Epithelium, Glands and Intercellular Junctions Simple squamous

4. Epithelium, Glands and Intercellular Junctions Simple cuboidal

5. Epithelium, Glands and Intercellular Junctions Simple columnar (with a brush border of microvilli) – in the picture at right, there are also goblet cells and intraepithelial lymphocytes

6. Epithelium, Glands and Intercellular Junctions Pseudostratified columnar with kinocilia and goblet cells

7. Epithelium, Glands and Intercellular Junctions Stratified squamous epithelium Connective tissue

8. Epithelium, Glands and Intercellular Junctions Urinary or transitional epithelium

9. Epithelium, Glands and Intercellular Junctions Urinary or transitional epithelium

10. Epithelium, Glands and Intercellular Junctions goblet cells intra-epithelial lymphocytes brush border of microvilli

11. Epithelium, Glands and Intercellular Junctions Mucus demonstrated with a PAS special stain

12. Epithelium, Glands and Intercellular Junctions

13. respiratory epithelium – the mucociliary clearance apparatus

14. Epithelium, Glands and Intercellular Junctions respiratory epithelium – the mucociliary clearance apparatus

15. Classifying glands by mode of secretion apocrine secretion merocrine secretion Holocrine mode of secretion

16. Glands lumen epithelium connective tissue

17. Glands Classifying glands by path of release of products exocrine paracrine endocrine

18. Glands fold or a gland?

19. Glands simple tubular gland

20. Glands Simple, unbranched, coiled, tubular gland the duct can be simple or compound the secretory portion can be branched or unbranched straight or coiled alveolar or tubular or tubular-alveolar

21. Glands tubular alveolar

22. Glands Compound, branched, tubular-alveolar Simple, branched alveolar Simple (unbranched) alveolar Zero or one generation of duct

23. Serous Mucous (both are merocrine, exocrine) - nucleus is central - small storage granules - abundant R.E.R. - watery secretion - secretions may have intense staining - small, distinct Golgi region - nucleus is flattened to the base - large storage granules - sparse R.E.R. - mucous secretion (thick) - pale granules (blue, grey or clear) - large Golgi region Golgi region RER

24. Intercellular Junctions ZO = zonula occludens = tight junction ZA = zonula adherens = intermediate junction (this is similar to the fascia adherens of the cardiac intercalated disk) D = desmosome = macula adherens

25. Intercellular Junctions ZO = zonula occludens = tight junction ZA = zonula adherens = intermediate junction (this is similar to the fascia adherens of the cardiac intercalated disk) D = desmosome = macula adherens desmosomes contribute to the strength of skin epithelium, intercalated disks, and holding epithelia to basal laminas (i.e., to connective tissue)

26. Intercellular Junctions ZO = zonula occludens = tight junction ZA = zonula adherens = intermediate junction (this is similar to the fascia adherens of the cardiac intercalated disk) D = desmosome = macula adherens desmosomes contribute to the strength of skin epithelium, intercalated disks, and holding epithelia to basal laminas (i.e., to connective tissue)

27. Intercellular Junctions ZO = zonula occludens = tight junction ZA = zonula adherens = intermediate junction (this is similar to the fascia adherens of the cardiac intercalated disk) D = desmosome = macula adherens gap junction = macula comunicans