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Endocrine System Definition

ENDOCRINES (DUCTLESS GLANDS) The several ductless glands are distributed in different parts of the body, and secrete chemical substances known as hormones or internal secretions. They act in unison and harmony with each other, in their common purpose of controlling, coordinating, and stimulating all vital body functions, such as secretion, metabolism, growth, and reproduction.

In their united and harmonious way of affecting the body functions they are similar to the nervous system, except that the nervous system accomplishes its mission through a network of wires (nerves) which really carry electric currents, while the ductless glands accomplish their purpose by a wireless system of throwing minute quantities of powerful chemical substances into the blood and lymph channels (vessels), and in that fashion reaching and affecting every tissue, organ and function of the body.

The secretions of these glands are absorbed directly by the small blood and lymph vessels in the ductless glands, without passing through ducts or secretory tubes as is the case with all other glands; that is why they are called the ductless glands.

When any one of the ductless glands is affected by underdevelopment or over development, by excessive secretion or deficient secretion, certain well-known and serious diseases or profound changes in the body are produced. There are still in the body many more internal secretions or hormones of which we have no knowledge or understanding. Some of the known internal secretions are discussed below.


Pituitrin is one of many hormones secreted by one of the most vital glands in the body, the pituitary gland, which is situated in the skull below the brain and just above the back part of the nasal cavity. The posterior portion or lobe of this gland secretes pituitrin, a hormone known a long time, which regulates the contractions of the involuntary muscles of the intestinal and genito urinary tracts.

Extracts of animal pituitary glands have therefore come to be used in medicine as an injection to in-crease labor pains or contractions of the uterus, thus hastening delivery. The several hormones secreted by the anterior lobe of the pituitary gland have been discovered more recently; they are known to control the growth of the bones and regulate the activity of the male and female sex glands, influencing menstruation, ovulation and lactation.

Overdevelopment and increased secretion of this lobe in childhood causes the phenomenon of gigantism or increased growth of the bones. The next time you go to the circus and see a 10-foot giant you will know how he got that way.

Midgets suffer from a lack of this secretion. Increased activity and secretion of the anterior lobe in mature persons causes a disease known as acromegaly, in which all the bones of the body, Instead of growing in lenghth, become extremely thickened.

You have probably noticed such people, with unusually large, protruding jaws, heavy brows, high heads, thick, stubby fingers and extremely broad shoulders.
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