Question

Simple columnar epithelium ( depicts a section through the wall of the small intestine – the same structure seen on your slide) a. This sort of epithelium lines some ducts, the stomach, and the intestine. Explain the possible significance of simple cuboidal epithelium lining some ducts and simple columnar epithelium lining other ducts.

1. The epithelial lining of the small intestine features a brush border. Identify the brush border, and indicate why this term might be appropriate.

2. What is the relationship between microvilli and the brush border? Summarize the ultrastructure of microvilli (structure beyond the level resolvable with a light microscope).

3. What is the probable significance of the brush border in the small intestine, given the absence of this feature from epithelia lining the lumen of other portions of the gastrointestinal tract?

4. Identify goblet cells in the epithelium lining the small intestine. What is the function of the product secreted by these unicellular glands within the epithelium?

5. What other epithelia can you see in the cross section of the small intestine? Where are these epithelia found? Describe the structures of epithelia you can see in a section of the small intestine.

Answer 1

Simple cuboidal epithelium is found in those structures which are meant for secretions and diffusion like salivary gland and renal tubules. Where as columnar cells are present where there is need of absorption like small intestine.

-Microvilli are thousands of microscopic projection of small intestinal mucosa.

- The structure formed by thousands of microvilli is called brush border epithelium

3. The significance of brush border in small intestine is that it increases surface area for absorption of nutrients in the small intestine.

4. Goblet cells secrete mucus which contains mucins,glycoproteins etc. Its main function is the lubrication of the gi tract to facillitate the food peristalsis.

5. Tall columnar epithelial cells are present which helps in absorption and called enterocytes.

Goblet cells are also present.