What is the term for glands that secrete substances directly into the bloodstream?

The term for glands that secrete substances directly into the bloodstream is "endocrine glands." These glands are a crucial component of the endocrine system and are responsible for producing hormones that regulate various bodily functions, including metabolism, growth, and mood. Endocrine glands, such as the thyroid, adrenal glands, and pituitary gland, release their secretions (hormones) directly into the blood, allowing for widespread distribution throughout the body.

In contrast, exocrine glands release their substances through ducts to specific areas, such as sweat glands or salivary glands. Serous and mucous glands refer to types of exocrine glands that produce specific types of secretions (serous being watery and mucous being thick), and they also do not secrete directly into the bloodstream. Understanding these differences clarifies why "endocrine glands" is the correct term for glands that have this direct secretion mechanism into the vascular system.