What do goblet cells primarily secrete?

Goblet cells are specialized epithelial cells found throughout the intestinal and respiratory tracts. Their primary function is to secrete mucins, which are glycoproteins that combine with water to form mucus. This mucus serves several critical roles: it lubricates and protects the epithelium from physical damage and pathogens, aids in trapping particles and microorganisms, and helps facilitate the passage of materials through the digestive system.

In contrast, the other options pertain to substances secreted by different types of cells in the body. Hydrochloric acid is primarily secreted by parietal cells in the stomach, and it aids in digestion and creating an acidic environment. Intrinsic factor, also secreted by parietal cells, is crucial for the absorption of vitamin B12. Pepsinogen, secreted by chief cells in the stomach, is an inactive precursor that gets activated to pepsin, an enzyme that digests proteins. Thus, the unique role of goblet cells in mucus production distinguishes them from other cell types involved in different secretory functions.