Final answer:
Mucous neck cells in the upper part of the stomach secrete acetic mucin, which is part of the gastric juice. The specific role of this mucus is not fully known.
Step-by-step explanation:
The cell type that secretes acetic mucin in the stomach is the mucous neck cells. These cells are located in the gastric glands in the upper part of the stomach. They produce a thin, acidic mucus, which is different from the alkaline mucus secreted by the goblet cells of the surface epithelium. Although the exact role of this mucus is not fully understood, it is part of the complex digestive fluid known as gastric juice.
The gastric glands contain a variety of secretory cells, including parietal cells, which produce hydrochloric acid (HCl) and intrinsic factor, and chief cells, which are responsible for secreting pepsinogen, the precursor to pepsin.