Which compartment is full of folds that absorb water and trap larger particles?

• A. Omasum
• B. Rumen
• C. Reticulum
• D. Abomasum

Answer: (A)

The main idea is how different parts of the ruminant stomach specialize for processing ingested feed. The omasum is lined with many folds (laminae) that greatly increase surface area and act like a sieve. As material moves into the omasum, water and some minerals are absorbed through the folds, and the folds trap larger particles, preventing them from moving too quickly to the next chamber. This filtration and dehydration prepare the ingesta for digestion in the true stomach. The other compartments have different roles: the rumen is the fermentation vat, the reticulum has a honeycomb lining that helps catch foreign matter and aids cud formation, and the abomasum is the true stomach where acid and enzymes digest proteins.