If two layers were oriented in this way in the wall of the digestive tube (as in the small intestine), what would happen to the diameter of the lumen of the tube when the fibers oriented along the length of the tube contracted?
When the fibers oriented along the length of the tube contract, the diameter of the lumen of the tube would decrease. This is because the circular layer of smooth muscle fibers within the wall of the digestive tube contracts radially, squeezing the tube and decreasing its diameter. This contraction helps to propel food through the digestive tract by creating peristaltic waves.
