Simple squamous epithelium can be studied by looking at cells which line blood and lymph vessels. These flattened cells are called endothelial cells . The nuclei are frequently found protruding into the lumen of the vessel. Observe the numerous large blood vessels present in the periphery of this section. Simple squamous epithelium is also the outer covering of the uterine tube which is termed the mesothelium .

Simple cuboidal epithelium is prominent in the cortex and medulla of the kidney. Proximal convoluted tubules , distal convoluted tubules , and collecting ducts are examples of simple cuboidal epithelium.

Locate a large fingerlike projection at the surface of the organ (this is an intestinal villus ). Observe that the projection has an internal component and a surface. The surface of each villus is covered with simple columnar epithelium . The free surface of these cells has very tiny projections called microvilli , which are specialized for absorption (absorptive cells). Numerous mucus-secreting cells, known as goblet cells because of their shape, are dispersed between the absorptive cells. In the lab or on Hippocrates, locate an electron micrograph of an intestinal absorptive cell and compare the details which you see in your light microscope with those seen on electron micrographs.

Note the ciliated, pseudostratified columnar epithelium lining the tracheal lumen. This epithelium is commonly referred to as "respiratory epithelium". Compare cilia with the microvilli on Slide 52. Note that the cilia are much longer. Study the ultrastructure of cilia and microvilli in electron micrographs.

Distinguish between the epididymis and the efferent ducts in this slide by the appearance of the lumen in each organ. The epididymis has a smooth, even epithelium lining its lumen; while the efferent ducts are more scalloped in appearance. Both are examples of pseudostratified columnar epithelium. Especially note the stereocilia (long microvilli) of the epididymis.

Stratified squamous nonkeratinizing epithelium lines the lumen of the esophagus. This type of epithelium is found in mucous membranes.

Observe the thick cornified layer of stratified squamous keratinizing epithelium of the skin. Note the changes in cellular morphology and intercellular spaces as one moves from the basal cells to the lifeless keratinized cells on the surface. Slide 43 is typical of thick skin .

This slide is another excellent example of stratified squamous keratinizing epithelium .

Stratified columnar epithelium is often found at the junction between simple columnar epithelium and stratified squamous epithelium. The ducts of the salivary glands fit into this category and are shown in this slide. Also observe some stratified cuboidal epithelium lining the larger ducts found in this section (typically lying within connective tissue septa).

Note the presence of characteristic surface dome cells in the transitional epithelium .

In this slide, the ureter is preserved in various degrees of distention for better observation of the features of transitional epithilium. Compare the distended epithelium to the relaxed epithelium .

The basement membrane is clearly seen underlining the "respiratory epithelium". This is refractile and pink. Be able to identify the components of this structure at the ultrastructural level.

The basophilic tissue covering one surface is the epidermis of the skin. The cells of this covering are fastened together with a multitude of desmosomes. Examine the epidermis and try to resolve the cell borders , which stain lighter. Using the oil immersion lens, critically examine the zone between the cells and observe what appears like spiny projections . At mid point of each spine is where each desmosome is located. Desmosomes can be observed in the electron micrographs. Think about the dimension of a desmosome and reflect on what you were able to see with your light microscope and in the electron micrographs.

Observe the nuclei in the different strata of the epidermis . Here you can observe euchromatic nuclei (ones having more euchromatin, extended DNA, than heterochromatin, contracted DNA) and heterochromatic nuclei (ones having just the opposite proportion of euchromatin to heterochromatin). Note the nuclei which are closest to the surface of the epidermis. These will become part of the stratum corneum, the cornified layer of dead cells.

Note the arrangement of the glandular epithelium forming rounded masses of epithelial cells termed acini . The centrally located lumen of each is continuous with the duct system of the gland. Individual cells are pyramidal shaped. The nuclei are round and found basally while the secretory granules are located apically. Ultrastructurally, these acinar cells are typical of protein secreting cells.

Here the granules are eosinophilic and the basal region of each acinar cell is basophilic as it should be normally.

The parotid gland is a pure serous gland and thus made up of all serous acini . Note the prominent granules of the acinar cells.

Also organized as acini, the submaxillary gland secretes both serous and mucous products. Serous cells are more numerous in the submaxillary (also called submandibular) gland. Mucous secreting cells have flat nuclei located basally. The apical region typically appears empty due to the extraction of mucous in routine tissue preparation. Serous cells are often found capping mucous acini. These are called demilunes and are easily distinguished by their intensely staining granules.

This slide shows a more typical picture of serous and mucous cells in an H & E stained preparation study.

Another example of mucous cells and serous demilunes .

Observe Goblet cells in the simple columnar epithelium of the duodenum.