Final answer:
Parietal cells and chief cells are located in the pylorus and body of the stomach, with parietal cells producing hydrochloric acid and intrinsic factor, and chief cells secreting pepsinogen.
Step-by-step explanation:
The cells located in the pylorus and body of the stomach are chief cells, parietal cells, mucous neck cells, and enteroendocrine cells. Specifically, parietal cells are located primarily in the middle region of the gastric glands and are responsible for producing hydrochloric acid (HCl) and intrinsic factor. HCl activates the protein-digesting enzyme pepsin and helps to kill ingested bacteria, while intrinsic factor is necessary for the absorption of vitamin B₁₂ in the small intestine. On the other hand, chief cells are located primarily in the basal regions of gastric glands and secrete pepsinogen, the inactive precursor of pepsin, which is activated by HCl into pepsin.