What distinguishes endocrine glands from exocrine glands?

Endocrine glands are characterized by their mode of secretion, which involves releasing hormones directly into the bloodstream. This allows the hormones to circulate throughout the body and reach target organs or tissues, where they exert their effects. This direct entry into the circulatory system is fundamental to the function of the endocrine system, as hormones often act from afar and can regulate processes such as metabolism, growth, and reproduction.

In contrast, exocrine glands have a different mechanism; they secrete substances into ducts that lead to specific locations, such as onto epithelial surfaces or into body cavities. These substances can include enzymes or other secretions that have local effects rather than systemic effects like hormones do.

The other options do not accurately describe the unique qualities of endocrine glands. They highlight misconceptions regarding the function and secretion processes of these glands. Understanding the distinction between these two types of glands is crucial for comprehending how the body's various communication and regulatory systems function.