Reading: RR&K, Chapter 4
SLIDE 56i small intestine, rat (H&E)
(RR&K p487, Fig.1,2,3; p84, Fig 1)
The specimen on this slide is a cross section of the small intestine of the rat embedded in plastic. First, find the outer (non-luminal) surface or mesothelium of the intestinal wall. At higher power, identify at the outer surface a thin, pink-stained line representing the cytoplasm of the mesothelial cells. One can see a few irregularly spaced nuclei. Almost all of the nuclei appear as elongate bodies in this plane of section, a characteristic of squamous cells. Next, identify the inner (luminal surface), which shows several intestinal villi. The surface of each villus is covered with a simple columnar epithelium with a striated border. Identify the striated border, lateral intercellular spaces, and goblet cells. With the 40X objective lens in place, scan the whole epithelium around one or two villi, identifying longitudinally, obliquely, and transversely sectioned epithelial cells (both absorptive cells and goblet cells). Large blood vessels in the connective tissue that lie beneath the epithelium can be seen as round or elongate spaces (the blood has been washed out by vascular perfusion). Identify the endothelium (simple squamous epithelium) which lines the lumen of each vessel. The cytoplasm of the cells is difficult to identify because the cells are rather thin. The nuclei are elongate in shape and sometimes bulge into the lumen. In some slides, circular profiles of pancreatic acini can be observed. The lumen of each acinus is also lined by a simple columnar epithelium made up of secretory acinar cells which are pyramidal is shape.
Check list for SLIDE 56i:
SLIDE 56k small intestine (PAS)
(RR&K p487, Fig.1,2,3; p84, Fig 1)
Identify the luminal and non luminal surfaces of the small intestine. On the luminal surface identify the villi. The surface of each villus is covered with a simple columnar epithelium with a striated border. Using the higher power lens, identify longitudinally, obliquely, and transversely sectioned epithelial cells (both absorptive cells and goblet cells). Note the difference in staining pattern on this slide. The striated border, basement membrane, and secretory vesicles of goblet cells stain red with PAS. What do these red structures have in common? Can you find any other structures or cells that stain with PAS?
In some slides, the circular profiles of pancreatic acini can be observed. As noted previously, the lumen of each acinus is lined by a simple columnar epithelium made up of secretory acinar cells. Does PAS stain the contents of these secretory vesicles? Why?
Check list for SLIDE 56k:
SLIDE 90b oviduct, (H&E)
(RR&K p720, Fig.1,2)
This specimen contains a cross section of the human oviduct (uterine tube). Identify the luminal surface of the oviduct. This highly folded mucosa contains a simple columnar epithelium with underlying connective tissue. Identify two types of epithelial cells: ciliated cells and nonciliated cells. With the 40X objective lens study the epithelium and identify well preserved cilia at the apical surface of many of the cells. The dark red lines at the base of the cilia and running perpendicular to the cilia are due the presence of the basal bodies.
Check list for SLIDE 90b: 
SLIDE 70a trachea (H&E)
(RR&K p60, Fig.4.2; p552, Fig 1,2,3,4; p536, Fig 18.6)
This slide contains cross section of the trachea with a partially missing anterior wall. Examine the epithelium on the luminal surface of the trachea at low power. Note that there are several layers of nuclei. Ciliated pseudostratified columnar epithelium lines the trachea. Most of these nuclei are elongate, located near the surface of the epithelium, and belong to the columnar ciliated epithelial cells. Observe the cilia and identify the red-stained basal bodies found at their base. In addition, there are two other epithelial cell types present: goblet cells and basal cells. The goblet cells (uni-cellular glands) contain many unstained secretory vesicles at the apical surface. The basal cells have a round or elongate nucleus and are closest to the thick basement membrane. A relatively large number of small round nuclei at different levels of the epithelium belong to migrating connective tissue cells (mostly lymphocytes). Can you distinguish these from the basal cells? Look at the multi-cellular glands present on this slide and determine the type of epithelium that lines these glands and their associated ducts. Look for the thyroid gland adjacent to the trachea. It consists principally of round follicles, most of which have been distorted in this preparation. Within the follicle is a colloid material (the thyroid hormone precursor) which stains pink. In this preparation the colloid shows "chatter" marks, an artifact produced in cutting. The cells which make up the follicles constitute a simple epithelium. In some follicles the epithelium is simple cuboidal while other follicles are lined by a simple squamous epithelium. One can also find small aggregates or clumps of cells, the nuclei of which have the same characteristics as those of follicle lining cells. How would you explain such cellular configurations?
Check list for SLIDE 70a: 
SLIDE 94e testis and epididymis, mouse (H&E)
(RR&K p657, Fig. 21.22; p658,Fig. 21.23)
With your naked eye locate the epididymis. The epididymis consists of a single, long and very tortuous tubule, folded upon itself numerous times. When it is sectioned, it gives the appearance of many tubules, rather than a single tubule. Select a cross-section of a tubule with cells that are nearly free of vacuoles (these are artifacts). The wall of the tubule is lined with a pseudostratified columnar epithelium. It contains two cell types: columnar cells with stereocilia and basal cells. The columnar cells have a round or elongate nucleus located in the basal third of the epithelium. The cytoplasm has a well-developed Golgi complex (negatively stained) distal to the nucleus. At its luminal border the cell exhibits stereocilia (the fine wavy thread-like processes that extend into the lumen). Are basal bodies present? The basal cells have flattened nuclei in the immediate vicinity of the basement membrane. These cells are less numerous than the columnar cells. Sometimes, these cells are confused with the connective tissue and myoid cells that reside outside of the tubule. The lumen of the tubule contains spermatozoa (dark basophilic heads, eosinophilic midpieces and a single flagellum).
Check list for SLIDE 94e: 
1. Where are epithelia found?
2. What are the functions of epithelia?
3. What are criteria used to classify epithelia?
4. List the characteristics that define an epithelia.
5. Where would you expect to find simple squamous epithelium? What is its function?
6. Where would you expect to find pseudostratified columnar epithelium? Discuss its function and what type of cells can you find within this epithelium?
7. How would you distinguish cilia from microvilli and from stereocilia in an electron micrograph?
8. What is the criteria used to classify glands?
9. What are the functions of the basement membrane? What is the clinical significance of the basement membrane?
This unit examines epithelial tissue as a distinctive covering of all body surfaces, cavities and glands. Epithelial tissue serves several important functions including creating a selective barrier between the "outside world" and the underlying connective tissue, secreting or absorbing specific materials across its surface, and receiving sensory stimuli.