A secret (from the Latin secerno - to separate, to secrete) in physiology is a substance that is produced by specialized cells and secreted by them into the internal environment of the body, in the cavities of organs or outside.
Secretions play an important role in the functioning of many body systems. For example, digestive secretions produced in the digestive glands are involved in the digestion of food. Hormones are the secretions of endocrine glands. They regulate many physiological processes in the body.
Thus, secretions are necessary for the normal functioning of the human and animal bodies. Their violation can lead to the development of various diseases.