1. This shows you a section of a blood vessel illustrating a simple squamous epithelium (E). Note that the epithelium is so thin that the only thing you can really see of these cells are their flattened nuclei, which bulge into the lumen of the blood vessel. (The pinkish cells are red blood cells in the lumen of the blood vessel) Wheater, 1993

2. EPITHELIUM Following are a series of images and descriptions to assist you in learning the characteristics of epithelia and its various subtypes.

3. This shows a very thin, simple squamous epithelium (mesothelium) that has been spread onto a slide and stained so that you are looking down onto the tissue. Note that the cells are tightly packed together with little intracellular material (the dark lines indicate the cell boundaries). The nuclei are indicated by “N”. Wheater, 1993

4. This shows a section of the small intestine illustrating the simple columnar epithelium with microvilli (arrow) on the apical surface. Notice that the epithelium is a single layer of cells and that these cells are taller than they are wide. Note also the Goblet cells within the epithelium (GC). GC

5. This shows the simple columnar ciliated epithelium of the oviduct. Note that many of the cells contain cilia (C) extending from their apical surfaces. Note also the secretory cells (SC) that are nonciliated. C SC

6. This shows the pseudostratified columnar epithelium of the epididymis. This epithelium appears to be stratified but in fact all of the cells make contact with the basement membrane. Note that the epithelial cells contain stereocilia extending from their apical surfaces (arrows).

7. This shows a section of the dermal portion of the integument (skin). Seen in the center of the field are a number of cross-sections of a sweat gland. Notice that some of the tube-like structures have simple cuboidal epithelium (black arrow). This is the secretory portion of the sweat gland. Other parts of the gland have stratified cuboidal epithelium (green arrow). This is the duct of the sweat gland.

8. This shows a section of thin skin illustrating a stratified squamous epithelium that is keratinized (Ep). Notice that the outer portion of the epithelium consists of extremely flattened (almost scaly in appearance), dead cells (arrow). No noticeable organelles remain in these cells, hence this is termed a keratinized epithelium. Ep Connective Tissue

9. This shows the epithelium at the junction of the endocervix and ectocervix. Note the stratified squamous epithelium (nonkeratinized) on the left and the simple columnar epithelium on the right. Connective Tissue Stratified Squamous Simple Columnar

10. This shows a section of the nasal cavity illustrating the pseudostratified columnar epithelium with cilia. Goblet cells (GC) can also be distinguished here as the pale-staining epithelial cells. GC Connective Tissue

11. This shows the pseudostratified columnar epithelium of the trachea. Cilia extending from the apical surface of the epithelial cells can be seen much better than in the previous micrograph. Connective Tissue

12. This shows a section of the larynx illustrating pseudostratified columnar epithelium on the right and stratified squamous epithelium on the left. The cilia are difficult to discern at this magnification. Stratified Squamous Pseudostratified Columnar

13. This shows a section of the epithelium lining the cervix containing stratified columnar epithelium. Note that it is the shape of the cells adjacent to the free surface by which the epithelium is named (i.e. the surface cells here are columnar in shape) Connective Tissue

14. This illustrates the transitional epithelium lining the urinary bladder. Note that the epithelium is stratified and that the surface cells are of diverse shapes. This epithelium is distensible (can be stretched). The stretched cells tend to flatten while those not stretched tend to be dome-shaped and bulge into the lumen (arrow). Connective Tissue

15. This shows a section of the colon illustrating simple tubular glands (arrows) called the Crypts of Lieberkuhn (or intestinal crypts). Note that these appear in section as relatively simple invaginations of the surface epithelium. Connective Tissue Smooth Muscle

16. This shows a section of the duodenum illustrating finger- like folds termed villi that are lined with simple columnar epithelium. The epithelium contains Goblet Cells (GC; the almost empty-appearing cells within the epithelium). The epithelium also contains Crypts of Lieberkuhn as seen in the previous slide. Below the Crypts of Lieberkuhn are other glands that extend into the connective tissue termed Brunner’s Glands (BG). These are compound tubular glands. BG GC Villus

17. This shows a section of the submandibular gland illustrating the compound acinar type of gland. Note the presence of mucous (black arrow) and serous (green arrow) cells. The mucous cells typically appear empty with routine tissue processing because the secretory contents are lost during the preparation of the tissue. Also notice the ducts lined with simple columnar type of epithelium (D). D

18. This shows a section of a mammary gland illustrating a compound acinar (alveolar) type of gland. Note the abundant cross- sections of glandular material and the large duct (D). D

19. This illustrates the secretory cells of the mammary gland at higher magnification. Note that the secretory portion of the gland is lined by simple cuboidal epithelium (SC). SC

20. This shows a scanning electron micrograph of the epithelium of the oviduct (you are essentially looking onto the surface of the epithelium from within the oviduct). Some of the epithelial cells have cilia (C) while others have microvilli (M). C M

21. This shows a transmission electron micrograph of the oviduct epithelium illustrating cells that have cilia (C) and others that have microvilli (M) on their surface. Note the difference in size and composition of these structures. M C

22. This shows a higher magnification transmission electron micrograph of cilia. Note in the cross- sections of cilia (*) the arrangement of the microtubules within the cilium. *

23. This shows a transmission electron micrograph of cilia in cross-section. Note the characteristic arrangement of microtubules in the cilia (i.e. two central microtubules surrounded by 9 other pairs). Cilium Microtubules

24. This shows a transmission electron micrograph of the epithelium of the cervix. Seen are the apical portions of two epithelial cells. Note that the cell to the left has microvilli and cilia on its surface. Two basal bodies (BB) are associated with the cilia in the cell to the left. Also notice the junctional complex between the two cells. What other structures can you identify here? BB Zonula occludens Zonula adeherens Macula adherens

25. This shows another transmission electron micrograph of the cervix epithelium. Notice the junctional complex between the two epithelial cells.

26. This transmission electron micrograph shows the basal portion of an epithelium. Notice the basal lamina (BL) separating the epithelium from the underlying connective tissue (CT). CT BL Glycogen