What type of glands secrete chemicals (hormones) into the bloodstream?

Endocrine glands are specialized structures in the body that secrete hormones directly into the bloodstream. These hormones serve as chemical messengers that travel through the circulatory system to target organs and tissues, where they regulate numerous physiological processes, including metabolism, growth, reproduction, and mood. The unique characteristic of endocrine glands lies in their lack of ducts; instead, they release their secretions directly into the blood, allowing for widespread distribution and systemic effects on the body.

This is in contrast to exocrine glands, which release their products through ducts to specific locations, such as the skin or the digestive tract. Sebaceous glands and salivary glands are examples of exocrine glands, as they secrete substances like oil and saliva, respectively, directly onto surfaces rather than into the bloodstream. Therefore, the correct identification of endocrine glands is crucial for understanding how hormonal regulation works in human physiology.