Which system in animals is responsible for the secretion of hormones?

The endocrine system is responsible for the secretion of hormones in animals. This system comprises various glands that release hormones directly into the bloodstream, which then transport these chemical messengers to target organs and tissues throughout the body. Hormones play crucial roles in regulating a wide array of physiological processes, including metabolism, growth, reproduction, and responses to stress.

Each gland within the endocrine system, such as the pituitary gland, thyroid gland, adrenal glands, and pancreas, produces specific hormones that orchestrate these various functions. The coordinated action of these hormones allows animals to maintain homeostasis, adapt to changes in their environment, and execute complex behaviors.

In contrast, the other systems mentioned do not primarily focus on hormone secretion. The nervous system is more concerned with transmitting signals through neurons and facilitating quick responses to stimuli. The circulatory system supports the transport of hormones but does not produce them. The respiratory system is involved in gas exchange and does not play a role in hormone secretion. Thus, the endocrine system is distinctly characterized by its function in hormone production and release.