When embedding small intestine, how should the tissue be oriented to visualize all layers?

• A. Tissue wall on edge - all layers are visible
• B. Mucosa facing up
• C. Lumen side up
• D. Serosa outward

Answer: (A)

Focusing on how embedding orientation affects what you can see in a slide, placing the small intestine with the wall on edge positions the block so that the microtome cuts across the entire thickness of the intestinal wall. That plane yields a cross-sectional view showing all layers—the mucosa, submucosa, muscularis externa (usually two layers: circular and longitudinal), and serosa—in one section. This makes it possible to assess the architecture and relationships of each layer clearly.

If the lumen side or mucosa were facing up, or if the serosa were outermost, the cut would more likely traverse along the layers or present only parts of the wall in the section, making it difficult to visualize and evaluate all layers together.