Which system is composed of glands that secrete hormones?

The endocrine system is a complex network of glands that play a crucial role in regulating numerous bodily functions by secreting hormones directly into the bloodstream. These hormones act as chemical messengers that influence various physiological processes such as growth, metabolism, reproduction, and mood.

Each gland within the endocrine system, like the pituitary, thyroid, adrenal glands, and pancreas, has specific hormones it produces that target organs and tissues, initiating necessary responses. For example, insulin produced by the pancreas regulates blood glucose levels, while thyroid hormones regulate metabolism.

In contrast, the other systems listed have different primary functions: the digestive system is responsible for processing food and nutrient absorption, the immune system protects the body from infections and diseases, and the integumentary system, which includes skin and associated structures, primarily serves as a barrier to protect the body from external harm. Understanding the unique role of the endocrine system in hormone secretion highlights its importance in maintaining homeostasis within the body.