What system consists of ductless glands secreting hormones directly into the bloodstream?

The endocrine system is composed of a network of ductless glands that play a vital role in regulating various bodily functions through the secretion of hormones directly into the bloodstream. These hormones act as chemical messengers that travel throughout the body, influencing processes such as metabolism, growth and development, tissue function, and mood regulation, among others.

Ductlessness is a key feature of these glands, distinguishing them from exocrine glands that secrete substances through ducts to an epithelial surface or into the gastrointestinal tract. This direct hormonal secretion allows for a more widespread and efficient means of communication within the body, as hormones can reach target organs that may be located far from their site of production.

The nervous system, on the other hand, uses electrical signals and neurotransmitters for rapid communication. The cardiovascular system is primarily responsible for transporting blood, nutrients, and oxygen throughout the body, while the lymphatic system plays a role in immunity and fluid balance. Understanding the specific roles of these systems highlights why the endocrine system is uniquely suited for the function described in the question.