What type of glands secrete chemical substances into ducts that lead either to other organs or out of the body?

Exocrine glands are designed to secrete chemical substances through ducts either to other organs or directly out of the body. This includes a variety of glands that produce substances such as saliva, sweat, and digestive enzymes. For example, salivary glands, which fall under this category, release saliva into the mouth through ducts to aid in digestion.

Conversely, endocrine glands release hormones directly into the bloodstream without using ducts, targeting distant organs and tissues to regulate various bodily functions. The thyroid gland, although it is responsible for important hormonal production, also falls into the endocrine category since it releases thyroid hormones into the bloodstream rather than through ducts.

Overall, the defining feature of exocrine glands is their ductal secretion mechanism, making them crucial for local effects in various systems, as opposed to the systemic effects produced by endocrine glands.