Laboratory: Epithelial Tissue/Glands

TYPES OF EPITHELUIM:

Simple squamous epithelium

mesothelium - #74 (colon)

endothelium - #100 (vessel in external ear)

Simple cuboidal epithelium

#54 (thyroid follicles)

Simple columnar epithelium

#31 (duodenum)

#72 (stomach, surface mucous cells)

Stratified squamous epithelia

non-keratized - #25 (esophagus)

#23 (mouth)

keratinized - #100 (skinn, external)

#9 (skin, sole of foot)

#7 (skin, scalp)

Stratified cuboidal epithelium

#9 (skin, sweat gland ducts)

Transitional epithelium

#14 (ureter and bladder)

Pseudostratified columnar epithelium

#84 (trachea)

TYPES OF GLANDS:

Unicellular glands

Goblet cells - #35 and 35 (colon)

Non-ducted multicellular glands

#27 (stomach, surface mucous cells)

Serous and seromucous acini

#38 (submaxillary salivary gland)

Serous exocrin gland with endocrine tissue

#41 (pancreas)

"Typical" endocrine gland

#55 (parathyroid gland)

Apocrine secretion

#66 (lactating breast)(milkfat only)

Holocrine secretion

#7 (scalp, sebaceous glands)

Part I: EPITHELIUM

Simple epithelia

Simple Squamous:

Mesothelium:

Mesothelium lines the body cavities and the surface of certain organs such as parts of the gastrointestinal tract. Look at the very thin flattened single layer of squamous cells covering the viscera as seen in slide 74. In some regions the mesothelium has been artificially removed; in others it is lifted off, and in some regions it is tightly adherent (don't confuse the cross sections of smooth muscle with the simple epithelium). What is the anatomical term for this simple epithelium?

Endothelium:

The endothelium can be seen lining various sized vessels in slide 100. Note the single flattened (squamous) cell layer with flattened nuclei. What is the purpose of this simple epithelium?

Simple Cuboidal:

Thyroid gland cells (slide 54).

Note that epithelial cells of a single type can vary in shape depending on their functional state. You'll learn more about this in Dr. Smith's lecture on the Endocrine system.

Simple Columnar:

Epithelium lining the small intestine (slide 31).

Note the presence of an apical layer of microvilli. What is the function of this epithelium?

Epithelium lining the stomach (slide 72).

Stratified epithelia

Stratified Squamous

Esophagus (25).

Is this epithelium keratinized or nonkeratinized?

Skin (100,9,7).

Is this epithelium keratinized or nonkeratinized? Why?

Mouth (23).

Describe this epithelium.

1. In which layer do new cells arise? Can you find histologic evidence for this on your slides?
2. What structure separates the epithelium from underlying connective tissue?
3. How are cells of epithelium nourished?

Stratified Cuboidal

Ducts of sweat glands in skin (9).

Look for clusters of cross-sectioned coiled tubular structures. Can you distinguish these ducts from the sweat gland acini? Hint: This is one of my favorite exam questions!

Transitional epithelium

Ureter and Bladder (14).

The ureter is mounted in the center of the slide simply to same space. What determines the thickness and shape of surface cells in this epithelium?

Pseudostratified columnar

Trachea (84).

Why is this not a true stratified epithelium? How many cell types can you identify? What apical specialization occurs on some columnar cells?

Note the basement membrane. It is pink (eosinophilic) and easily seen by light microscopy.

Part II: GLANDS

#35, #36 (Colon: Example of unicellular gland (The Goblet Cell)

1. Identify the goblet cells in the colon epithelial lining.
2. Why does the apical cytoplasm look clear on Slide #35?
3. Compare slide #36 (PAS - Alcian Blue) with #35. What is staining brilliant blue on #36?
4. Are any other epithelial lining cells present in the colon? What is the relative proportion of these cells to goblet cells? What might the non-goblet cells be doing?

#27 (Stomach fundus): Example of non-ducted multicellular exocrine gland (Surface Mucous Cells)

1. Locate the stomach epithelial lining. It is a simple columnar epithelial composed of a sheet of non-ducted mucus-secreting cells - a multicellular gland. Don't be confused by the architecture - the lining is composed of gastric pits and glands. Don't look at the gastric glands now.
2. Are goblet cells present in the stomach?
3. How do surface mucous cells differ from goblet cells?

#38 Examples of serous and seromucous acini (Submasillary Salivary Gland):

1. This is one of the major salivary glands. Look for all-serous acini, and also for mixed seromucous acini.
2. How do the serous and mucous acinar cells differ? Do these serous cells stain similarly to pancreatic acinar cells? Why?
3. The ducts have larger, open lumens and more eosinophilic cytoplasm than the acinar cells. What are the functions of the ducts?

#41 Example of serous exocrine gland, with endocrine tissue also present (Pancreas):

1. Locate the exocrine serous pancreatic acinar cells. Explain why the apical and basal regions of cytoplasm stain by H & E as they do.
2. Locate ducts, with simple cuboidal or columnar epithelium.
3. On very low power, note the division of groups of acini into lobules.
4. Locate the endocrine component of the pancreas - the Islets of Langerhans. What characterizes the islets as endocrine tissue?

#55 Example of a typical endocrine gland (Parathyroid)

1. Locate the endocrine cells, which have dark round nuclei.
2. What characteristics of the parathyroid identify it as an endocrine gland?

Models of Secretion: