What is segmentation?

• A. Waves of peristaltic movement
• B. Cycles of contraction in the intestines that churn and fragment the bolus, mixing the contents with intestinal secretions
• C. Secretion of mucus
• D. Absorption of water

Answer: (B)

Segmentation refers to localized rhythmic contractions of the circular smooth muscle in the small intestine that churn and fragment the chyme, mixing it with intestinal secretions. This back-and-forth motion increases contact between the digested material and enzymes and the absorptive surface, promoting digestion and nutrient absorption. It differs from peristalsis, which uses waves of contraction to move contents steadily along the tract. Secretion of mucus or absorption of water describe different digestive processes, not segmentation.