A drop in pH below 4.5 in the duodenum stimulates the secretion of (a) secretin, (b) cholecystokinin, (c) gastrin, (d) all of these.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

d. The mucosa of the esophagus, pharynx, and oral cavity contains simple squamous epithelium to protect it from abrasion.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

b. The esophageal and pharyngeal phases of swallowing are mediated by the swallowing reflex of the brainstem and the enteric nervous system.