1. HISTOLOGY REVIEW Epithelia Dr. Tim Ballard Department of Biology and Marine Biology

2. Simple squamous epithelium Arrowheads indicate the locations of Bowman’s capsules within the cortex of the kidney. This is one place to locate simple squamous epithelium. Kidney – median sagittal section – H&E – 10x objective

3. Single layer of flattened cells with prominent flattened nucleus, very thin, lining the capsular space of Bowman’s capsule Simple squamous epithelium Kidney – median sagittal section – H&E – 40x objective Bowman’s capsule lumen

4. Flattened cells, one cell layer thick, lining the lumen of an artery Simple squamous epithelium Artery – cross section – H&E – 40x objective lumen

5. Simple cuboidal epithelium Kidney – median sagittal section – H&E – 10x objective Arrowheads indicate renal tubules in the kidney cortex. “Tubule” is a key word, telling you this is one place to locate simple cuboidal epithelium.

6. Kidney – median sagittal section – H&E – 40x objective Renal tubules (arrowheads) – note that the cells appear about as tall as they are wide and that there is a single layer of cells. Simple cuboidal epithelium lumen Approximate size of one cell Approximate location of basement membrane

7. In the renal medulla you find collecting ducts, lined with a single layer of simple cuboidal cells. Simple cuboidal epithelium Kidney – median sagittal section – H&E – 40x objective lumen

8. Simple cuboidal epithelium (arrowheads) forms follicles in the thyroid gland. Simple cuboidal epithelium Thyroid gland – cross section – H&E – 40x objective lumen

9. Duct (arrowhead indicates location of the basement membrane) within the pancreas. Note the single layer of simple cuboidal cells. Simple cuboidal epithelium Pancreas – section – H&E – 40x objective lumen

10. Villi (arrowheads) – finger-like processes inside the gallbladder. This organ of the digestive system is line with simple columnar epithelium. Simple columnar epithelium Gallbladder – section – H&E – 10x objective lumen

11. Note that the simple cuboidal cells are taller than they are wide. Simple columnar epithelium Gallbladder – section – H&E – 40x objective Basement membrane would be located along this line. Approximate size of one cell lumen

12. Although this looks different from the gallbladder, this is still simple columnar epithelium. Simple columnar epithelium Duodenum – section – H&E – 40x objective Basement membrane would be located along this line. Approximate size of one cell lumen

13. This is the signature epithelium of the respiratory system. Note the difference between epithelium above and connective tissue below the line. Ciliated pseudostratified columnar epithelium Trachea – cross section – H&E – 10x objective Basement membrane would be located along this line. lumen Underlying connective tissue epithelium

14. All cells contact the basement membrane, but not all cells reach the surface. It only appears stratified, hence the name. Ciliated pseudostratified columnar epithelium Trachea – section – H&E – 40x objective lumen cilia Basement membrane

15. You can tell this isn’t stratified columnar epithelium because no can’t discern individual layers. Stratified columnar would have clear rows of nuclei. Ciliated pseudostratified columnar epithelium Intrapulmonary bronchus – section – H&E – 40x objective lumen cilia Basement membrane

16. It is easy to see why this is called a stratified epithelium. I counted about 35 layers of cells stretching from the basement membrane to the apical surface. Stratified squamous epithelium Esophagus – section – H&E – 10x objective lumen Basement membrane How many layers of cells do you see here? Underlying connective tissue

17. Cells at the basal surface are cuboidal and mitotic. As new cells are pushed to the top, they become increasingly squamous in shape. (nonkeratinized) Stratified squamous epithelium Esophagus – section – H&E – 20x objective lumen Basement membrane

18. Again, look at the layers of cells between the basement membrane and the apical surface. Human skin – section – H&E – 10x objective Keratinized stratified squamous epithelium Basement membrane free surface Keratinized layers of cells

19. Cuboidal cells at the basal surface give way to increasingly flattened cells (squamous) in the upper layers. The cells are filled with water-proof keratin. Human skin – section – H&E – 40x objective Keratinized stratified squamous epithelium Free surface Keratinized layers of cells – very long, thin and flattened (scale-like) Basal surface Epithelium

20. Larger ducts of the body may have a stratified cuboidal epithelium, where the top layer of cells is cuboidal. There are usually only two layers of cells. Stratified cuboidal epithelium Submandibular (salivary) gland – section – H&E – 40x objective Apical layer of cells Approximate size of one apical cell lumen Basal layer of cells

21. Very large ducts of the body may have a stratified columnar epithelium, where the top layer of cells is columnar. There are usually only two layers of cells. Stratified columnar epithelium Submandibular (salivary) gland – section – H&E – 40x objective Apical layer of cells Approximate size of one apical cell lumen Basal layer of cells What is the epithelial type?

22. Transitional epithelium is the signature epithelium of the urinary tract. It is found in the ureters and urinary bladder. Transitional epithelium Ureter – cross section – H&E – 10x objective Epithelial layer lumen Basal layer of cells Underlying connective tissue layer

23. This is called transitional epithelium because the number of cell layers changes as the organ walls increase and decrease in tension. Transitional epithelium Ureter – cross section – H&E – 40x objective Apical layer of cellslumen Basal layer of cells When the organ walls are under low tension, the epithelium has 6 – 8 layers of cells.

24. The urinary bladder looks different from the ureter because it is a different organ with different function, but the epithelium is still transitional. Transitional epithelium Urinary bladder – section – H&E – 10x objective lumen Basement membrane

25. The distinguishing features of this epithelium are multiple layers and the very large “sofa pillow-like” cells at the apical surface. Transitional epithelium Urinary bladder – section – H&E – 40x objective Apical layer of cells lumen Basal layer of cells Basement membrane end