Label the parts I-V of the gastric pit and explain how parietal, chief, and enteroendocrine cells contribute to gastric juice formation.

Here is the solution to your question: a) Label the parts I-V: I. Gastric pit (or Surface mucous cells) II. Mucous neck cells III. Parietal cells (or Oxyntic cells) IV. Chief cells (or Zymogenic cells) V. Enteroendocrine cells (or G cells) b) How III, IV and V contribute to the formation of gastric juice: • Parietal cells (III) secrete hydrochloric acid (HCl), which lowers the stomach pH, denatures proteins, and activates pepsinogen. They also secrete intrinsic factor. • Chief cells (IV) secrete pepsinogen, which is converted to pepsin by HCl to begin protein digestion, and gastric lipase for fat digestion. • Enteroendocrine cells (V), specifically G cells, secrete the hormone gastrin, which stimulates parietal cells to produce HCl and chief cells to produce pepsinogen, thereby regulating gastric juice production.