What system integrates many body functions and includes the release of hormones?

The endocrine system is the correct choice because it is responsible for the production and secretion of hormones, which are chemical messengers that regulate various physiological processes throughout the body. Hormones are released into the bloodstream and can affect organs and tissues far from their site of release, allowing for widespread integration and control of multiple body functions. This system plays a crucial role in maintaining homeostasis, influencing growth, metabolism, mood, and reproductive processes.

In contrast, the nervous system primarily uses electrical signals for communication and coordination but is distinct from the hormonal regulation that characterizes the endocrine system. The circulatory system is involved in the transportation of hormones, nutrients, and gases but does not control bodily functions through hormone release. The digestive system primarily focuses on the breakdown of food and nutrient absorption, rather than hormonal integration of multiple body functions. Thus, the endocrine system is the most accurate descriptor of a system that integrates many body functions through hormone release.