Final answer:
Segmentation in the small intestine involves contractions that mix chyme with digestive juices, aiding in nutrient absorption. As chyme is absorbed and the intestine becomes less distended, segmentation gives way to the migrating motility complex, propelled by motilin, that moves chyme along the intestine.
Step-by-step explanation:
The second rotation of the midgut refers to embryological development and involves movement and differentiation of the primitive gut and its associated structures. However, the context provided here appears to be discussing the physiological movements of the midgut in the small intestine after birth, specifically the process of segmentation and the role of the migrating motility complex. During the segmentation of the small intestine, the muscular contractions create back-and-forth movements that mix digestive juices with food particles (chyme) and enhance absorption by pushing chyme against the mucosa. The duodenum has the most rapid segmentation compared to the ileum. Following the absorption of chyme, less distended intestinal walls signal a switch to transport movements, led by the hormone motilin and characterized by the migrating motility complex, which slowly moves chyme down the intestine.