Identify Brunner's glands (Fig. 15-34) and small aggregates of lymphocytes on slide 4. Classify Brunner’s glands as to staining property (serous or mucous) and mode of secretion.

On slide 4 find groups of villi cut longitudinally and identify

• Capillaries,
• Lacteals, and
• Smooth muscle fibers in the lamina propria of each villus (Fig. 15-33).

Then examine the epithelial surface of the villi, identifying goblet cells, the striated border on enterocytes, and crypts at the bases of adjacent villi (Fig. 15-27 and 15-28). Identify mitotic figures in epithelial cells of the crypts. Paneth cells (Fig. 15-30) in the lining of the crypts are best seen on slides 50 and 37, which are H&E stained.

Which is more readily visible in a villus, the capillaries or the lacteal?

Why are enterocytes said to have a “striated or brush border?”

Examine the ultrastructural features of enterocytes, especially their apical and basal surfaces, in Fig. 15-28 and 15-29.

• Note at the apical end especially the glycocalyx, microvilli,
• The terminal web, and
• The formation of endocytotic vesicles

At the basal-lateral surface, note the close association with a capillary for transfer of absorbed molecules and the movement of fatty chylomicrons from the intercellular cleft into the lamina propria for uptake by lacteals.

What is the functional significance of each of the following?

• glycocalyx on microvilli:
• endocytotic vesicles:
• intercellular cleft:

But things don't always go as designed.