Jejunum (400X)

Try to identifythe following structures:

• secretory granules within paneth cells at the bottom of crypts
• mucin inside goblet cells
• lamina propria
• lamina muscularis mucosae
• longitudinal section through an arteriole in the submucosa
• a fibroblast in the submucosa (easily differentiated from the smooth muscle cells of the lamina muscularis mucosae
• cells due to its heavy red stain)

What are paneth cells and where are they located?

- Paneth cells are secretory cells that secrete bactericidal substances into the intestinal lumen. They are found at the bottom of the crypts of Lieberkuhn / intestinal glands.

How is the lamina muscularis mucosae built up?

- The muscularis mucosae consists of smooth muscle cells; an inner circular and an outer longitudinal layer (each of the layers is 1-3 cell thick)