Final answer:
Endocrine glands, such as the thyroid and pituitary, secrete hormones directly into the bloodstream without the use of ducts, playing a key role in the body's regulatory system. They are part of the endocrine system, distinct from exocrine glands that secrete substances through ducts.
Step-by-step explanation:
The glands referred to in the question are endocrine glands, which are tissues or organs that secrete hormones directly into the bloodstream and lymph, without the use of ducts. This allows the hormones to be transported to organs distant from the site of secretion. The endocrine system, a crucial regulatory system in the body, includes glands such as the thyroid and pituitary.
The pituitary gland, often known as the master gland, regulates other endocrine glands in the body by secreting various hormones that influence their activity. For instance, the pituitary gland can secrete thyroid-stimulating hormone, which will then travel to the thyroid gland to regulate its activity. The thyroid gland is another example of an endocrine gland and is responsible for regulating metabolism and other important bodily functions through the release of its hormones.
In contrast to endocrine glands, exocrine glands release their secretions through ducts to nearby body surfaces. Examples of exocrine glands are sweat and salivary glands.