Simple columnar (Fig. 4-13)

• Simple columnar epithelia are specialized for absorption.
• This type of epithelium lines the gall bladder (slide 3).
• The projecting villi in the small intestine (slide 4).
• The apical ends of these epithelial cells are covered by microvilli to provide a larger surface for absorption.

Examine both the LM and EM pictures of microvilli in Fig. 4-8.

• On slide 4 the glycocalyx on the microvilli is stained "magenta" by the PAS reaction, demonstrating the microvilli collectively as the brush border or striated border.
• On slide 21, stained with trichrome, study the brush border again and examine the terminal web, the network of actin filaments in the cytoplasm just below the microvilli.
  • Draw several columnar epithelial cells, showing the nuclei, the apical ends, microvilli, and glycocalyx.
• Some cells of the simple columnar epithelium on slide 4, called goblet cells, are specialized for secretion rather than absorption.
  • PAS stains the mucin granules which fill the cytoplasm, demonstrating the overall size and shape of these cells. See also Fig. 4-17

Here are some interesting facts about epithelial cells.