Which statement best describes the relationship between the ileum and the large intestine?

• A. It finishes absorbing vitamins, solids, and nutrients from the chyme before it passes into the large intestine
• B. It passes chyme directly into the colon without absorption
• C. It stores waste before elimination
• D. It secretes enzymes that digest carbohydrates

Answer: (A)

The key idea is how the ileum completes absorption before material enters the large intestine. The ileum is the last segment of the small intestine, and it continues the work of absorbing nutrients, including vitamins and other substances that escaped earlier digestion. It is especially important for reabsorbing bile acids and vitamin B12, along with some remaining nutrients and water. By the time chyme moves into the large intestine, most nutritional absorption has already occurred, and the large intestine’s primary roles are to absorb water and electrolytes and to form feces with help from gut bacteria. The large intestine does not secrete significant digestive enzymes, and waste storage happens primarily in the rectum, not in the ileum. Thus, the statement that best describes their relationship is that the ileum finishes absorbing vitamins, solids, and nutrients from the chyme before it passes into the large intestine.