What is the primary function of the endocrine system?

The primary function of the endocrine system is to regulate bodily functions through hormones. This system comprises various glands that secrete hormones directly into the bloodstream, allowing these chemical messengers to travel throughout the body and target specific organs and tissues. Hormones play crucial roles in numerous physiological processes, including metabolism, growth and development, tissue function, and mood regulation. By using the bloodstream for communication, the endocrine system can coordinate complex bodily functions over a longer duration compared to the nervous system, which operates through electrical signals for immediate responses.

In contrast, the other functions listed relate to different systems within the body. The role of protecting the body and regulating temperature is primarily served by the integumentary system, which includes the skin and its associated structures. Providing structural support is the main function of the skeletal system, which consists of bones and cartilage. Finally, the transport of nutrients and waste in the blood is primarily the responsibility of the circulatory system, which comprises the heart, blood vessels, and blood itself. Thus, option C accurately describes the unique and essential function of the endocrine system.