Which type of gland produces an internal secretion that is discharged into the blood or lymph?

The type of gland that produces internal secretions released directly into the blood or lymph is the endocrine gland. These glands are a crucial part of the endocrine system, which regulates various bodily functions by releasing hormones. Hormones are chemicals that serve as messengers in the body, influencing processes such as metabolism, growth, and mood among others.

Endocrine glands, such as the pituitary gland, thyroid gland, adrenal glands, and pancreas, do not have ducts and instead secrete hormones directly into the bloodstream, allowing for widespread distribution throughout the body. This direct release enables the hormones to reach target organs and tissues to elicit specific responses.

In contrast, options like exocrine glands, which produce secretions that are released through ducts to an external surface or into cavities (like sweat, saliva, or digestive juices), do not release their substances into the bloodstream. Salivary and sweat glands are specific examples of exocrine glands, which operate differently from endocrine glands in terms of secretion pathways and functions.