Human Anatomy and Physiology - N. I. Fedyukovich 2003

Endocrine Glands

The processes occurring within the body are regulated not only by The Nervous system, but also by the ductless glands (the Endocrine System). These comprise specialized, topographically separated glands of diverse origins that lack excretory ducts and secrete their synthesized products directly into the Blood AND Lymph. The products of endocrine gland activity are known as Hormones.

Hormones are highly potent agents; consequently, only minute amounts are required to elicit a specific physiological effect. Some hormones accelerate the GROWTH AND DEVELOPMENT of Organs and systems, while others regulate METABOLISM, govern behavioral responses, and so forth. Anatomically distinct Endocrine glands exert mutual influence upon one another. Because this interaction is mediated by hormones delivered via the bloodstream to target organs, it is customary to speak of the humoral regulation of these organs operating via a feedback mechanism. As a result of this feedback loop, hormone concentrations in the blood are maintained at levels optimal for the Organism. Nevertheless, it is well established that all processes occurring within the body remain under the constant Supervision of the Central Nervous System. This dual regulation of organ function is referred to as neurohumoral regulation. Any alteration in endocrine gland function can lead to severe physiological disorders and diseases, including psychological disturbances.

In The Human Body, the endocrine glands are distributed as follows (Fig. 86): in the Brain region—the Pituitary Gland and the Pineal Gland; in the neck and chest regions—the thyroid, parathyroid, and Thymus glands; in the Abdominal cavity—the Pancreas and the Adrenal Glands; and in the pelvic region—the Ovaries and Testes.