Question
From the esophagus down, the 6-9 meter long digestive tube is made up of four layers: the inner (A)__________ of epithelial cells, a sub mucosa, smooth muscle, and serosa. Nutrients from the tube are absorbed across the layers into the bloodstream.
(B)__________ are circular muscles that control the flow of food through the digestive tract.
(B)__________ are circular muscles that control the flow of food through the digestive tract.