What is one of the primary functions of exocrine glands, such as salivary glands?

Exocrine glands, like salivary glands, perform the essential function of secreting substances directly onto epithelial surfaces. This is accomplished through ducts that transport these secretions to specific sites, such as the mouth in the case of salivary glands. These secretions can include enzymes, mucins, and other substances that play vital roles in digestion and maintaining oral health.

In contrast, other options describe functions that do not align with the role of exocrine glands. Producing hormones for systemic circulation is a primary function of endocrine glands, which release hormones directly into the bloodstream instead of through ducts. The storage of chemicals for future use pertains more to organs like the liver or certain endocrine glands rather than exocrine glands. Filtering toxins from the bloodstream is a function associated with organs such as the kidneys and liver, which processes substances rather than secreting them outwardly. Thus, the primary role of exocrine glands in secreting to epithelial surfaces is distinct and crucial for various bodily functions.