Once the undigested and unabsorbed substances enter the caecum, their backflow is prevented by

Question

Accepted Answer

A. 1. **Locate the caecum.** The caecum is the pouch-like structure where the small intestine (ileum) joins the large intestine, and undigested/unabsorbed food material passes into it from the ileum.

2. **Identify the valve at this junction.** So, at this specific ileum–caecum junction, there is a valve called the **ileo-caecal valve**, whose job is to allow one-way movement of material and prevent it from flowing backward into the ileum.

3. **Eliminate the other structures.** The **gastro-oesophageal sphincter** controls the opening between the oesophagus and stomach, the **pyloric sphincter** controls the opening between the stomach and duodenum, and the **sphincter of Oddi** controls the opening of the common hepato-pancreatic duct into the duodenum — none of these are located near the caecum.

4. **Conclusion.** Hence, the backflow at the caecum is prevented by the **ileo-caecal valve**, making **Option A** correct.