Endocrine System

The body contains two kinds of glands: exocrine and endocrine. Glands are a collection of specialized cells which secrete substances into the body. Exocrine glands (sweat, mucus, digestive and salivary glands), secrete substances such as sweat, oil and saliva, into ducts which are then carried into body cavities. Endocrine glands secrete dozens of chemical messengers called hormones, and release them into the bloodstream to regulate all the systems in the body. The endocrine system is made up of nine major glands: the adrenal glands, pancreas, parathyroid, pineal gland, pituitary gland, male and female sex glands, thymus and thyroid gland.

All hormones are made up of proteins. Hormones are part of another exceedingly complex message system, important for the collective work the organs and tissues perform in harmony.

The adrenal glands lie on top of the kidneys, and their secretions regulate metabolism and maintain proper levels of sodium and potassium in the blood. The pancreas (which is an organ, as well as a gland) is located behind and a little lower than the stomach. Its most important function is to produce insulin, the hormone that breaks down glucose.

In the brain, lie the pineal and pituitary glands. The pineal gland releases melatonin which is responsible for maintaining the body's internal clock and rhythms. The pituitary is the most important gland in the endocrine system because the hormones it releases control other endocrine glands. The sex glands are responsible for the development and maintenance of the reproductive system. The ovaries, which produce estrogen and progesterone, lie in a woman's pelvic cavity; in men, the testes, which produce testosterone, are located in the scrotum.

Behind the sternum, between the lungs, is the thymus, and its hormones promote the production and maturation of infection-fighting T cells. Below the larynx (voice box) is the thyroid, a U-shaped gland with lobes lying on either side of the trachea. It is the only gland to store its secretions in large quantities. The thyroid regulates metabolic rate. Attached behind the thyroid is the parathyroid. Its hormones increase the number and activity of bone-destroying cells, which are important for releasing calcium into the blood.

Since many hormones are activated by the liver, the health of this organ is vital for hormone health. Regular doses of sunshine have been found to have a regulatory effect on the endocrine system, and help certain cases of overactive thyroid, depression, developmental disturbances and absent menstrual periods.

The endocrine glands can become ill from autoimmune processes, viruses and bacteria like any other body system. A weakened immune system, psychological stress and physical exhaustion all affect the hormonal system adversely. Some hormones, such as the human growth hormone, are regulated by patterns according to sleep and waking cycles, or the passage of night and day.

PDF Diagram of the Endocrine System