Villi Explorer¶
Run the Villi Explorer MicroSim Fullscreen
About This MicroSim¶
The small intestine is lined with intestinal villi, tiny finger-like projections covered in even tinier microvilli. Together they give the intestine a huge surface for absorbing nutrients. In celiac disease, eating gluten (a protein in wheat, barley, and rye) sets off an immune reaction in the lining. Over time the villi shorten and flatten, a change called villous atrophy, and the intestine absorbs less.
This MicroSim shows a magnified strip of lining. You choose whether the person has celiac disease and whether they eat gluten, then watch the months go by:
- Has celiac disease + Eats gluten: purple immune cells crowd in, tTG antibodies rise, the villi shrink, and absorption drops.
- Has celiac disease + Gluten-free diet: symptoms settle within weeks, antibodies fall over months, and the villi grow back slowly.
- Does not have celiac disease: the villi stay tall on either diet, because gluten doesn't trigger an immune attack.
The Run tests button reports a tissue transglutaminase (tTG) antibody blood test and a small bowel biopsy result for the current moment. Running the tests after switching to a gluten-free diet shows why doctors test first.
How to Use¶
- Keep Has celiac disease and Eats gluten. Predict what will happen to the villi, then press Start.
- After several simulated months, press Run tests. Read the blood test and biopsy results.
- Switch the diet to Gluten-free diet. Compare how fast the Symptoms meter falls with how fast Villus height recovers.
- Press Reset. Let the villi shrink again, switch to gluten-free, wait about a year and a half of simulated time, and then press Run tests. What changed?
- Choose Does not have celiac disease and try both diets.
Learning Objective¶
Bloom level: Understand. The learner will explain how gluten exposure in celiac disease causes villous atrophy and reduces absorption, why villi stay normal in people without celiac disease, and why testing must happen before starting a gluten-free diet.
Iframe Embed Code¶
<iframe src="https://aaryavvatts-lab.github.io/gut-brain-textbook/sims/ch12-villi-explorer/main.html" height="562px" width="100%" scrolling="no"></iframe>
Lesson Plan¶
Grade level: 9 to 12 (biology, anatomy and physiology, health science)
Duration: 20 to 25 minutes
Activity:
- Warm-up (3 minutes). Show a photo of a gluten-free menu. Ask: "Who actually needs to avoid gluten, and why?" Collect answers.
- Explore (7 minutes). In pairs, students run steps 1 to 3 and sketch the villi at month 0, at their shortest, and after a year gluten-free.
- The testing trap (6 minutes). Students run step 4 and explain in one sentence why the tests changed.
- Control comparison (4 minutes). Students run step 5 and explain why the person without celiac disease is the "control" in this model.
- Limits (3 minutes). Read the "What this model leaves out" box in Chapter 12 and name one simplification.
Assessment questions:
- Why does flattening of the villi reduce absorption of nutrients such as iron?
- Why do symptoms improve faster than the villi heal on a gluten-free diet?
- Why can starting a gluten-free diet before testing make celiac disease harder to diagnose?
- Why do the villi stay normal in the person without celiac disease, even when they eat gluten?