What does the muscular layer do?

• A. Absorbs nutrients.
• B. Contracts to move materials through the canal.
• C. Secretes mucus.
• D. Produces bile.

Answer: (B)

The muscular layer (muscularis externa) is responsible for motility. Its smooth muscle fibers contract rhythmically to move and mix contents as they travel through the canal. The inner circular layer constricts the lumen, while the outer longitudinal layer shortens the tube; together these actions create peristaltic waves and segmentation that propel material along and mix it for digestion. This movement is coordinated by the enteric nervous system, ensuring efficient propulsion of contents.

Absorption happens mainly in the mucosa, which houses absorptive cells. Mucus secretion is produced by goblet cells in the mucosa. Bile production is a liver function, not part of the intestinal muscle layer.