Sophronia L. Gallop
The endocrine glands, ductless glands which pour their secretions directly into the blood stream. The first scientific study of the endocrine glands was made by Berthold in 1849 when he observed that the hemlike changes in the body build and behavior which occurred in castrated cocks could be reversed by transplanting healthy testes into the operated animal. This effect resulted from the secretion of hormones from the transplanted tissues into the blood stream of the cock.
The endocrine system includes the pituitary gland, the thyroid, the adrenals, the ovaries, the testes, the parathyroids, the pancreas, and in pregnancy, the placenta (the afterbirth). While the structural features of these glands are different, they are all alike in having a large number of secretory cells, a well-developed blood supply, and no ducts.
The endocrine secretions, the hormones, are often aptly described as “chemical messengers,” since by their action they enable one part of the body to regulate the activity of another part. Hormones help control the pace of body activity, the rate of growth, the reproductive cycles, and the physical characteristics which distinguish men from women. The hormones are not usually stored to any great extent in the glands or the tissues and they must, consequently, be continuously produced. The exact mechanism of their action is not known, but it has been established that hormones alter the rate of metabolic reactions rather than initiate them. All hormones bind a receptor on their target cells. Some hormone receptor complexes effect enzyme reactions, while others act on the DNA in the cell nucleus or promote the release of packaged hormones. Hormones are generally effective in minute amounts. Comparatively small fluctuations in the supply of these substances can spell the difference between a normal individual and a dwarfed, deformed, or mentally retarded person.
As you can see from the diagram, the endocrine glands are pretty well scattered throughout the body. Location is unimportant because hormones can reach any part of the body in seconds, and only tiny amounts are needed. For example, the entire quantity of adrenalin in your blood, under emergency conditions, would be much less than 1/1,000,000th of an ounce. Other hormones circulate in larger amounts than this, but the amounts are still very tiny. Yet these hormones have a tremendous influence on the workings of the entire body.
Puberty is a time of growth and change for both boys and girls. The process of puberty begins when male and female hormones are released into the bloodstream. Hormones are chemicals which cause body growth and change.
During puberty both boys and girls will:
Grow very quickly.
Sometimes feel clumsy.
Perspire more and have body odor.
Develop oily skin and some pimples.
Notice aching muscles and joints. (Yes, “growing pains” are real!)
Even though lots of the changes are the same, girls usually begin puberty a year or two before boys.
BOYS
Between the ages of 10 and 16, boys’ bodies begin these changes:
-
*Shoulders broaden.
-
*Muscles grow.
-
* Hair grows under arms; on arms, legs, chest and face; and around penis and testicles (pubic area).
-
* Penis and testiclesgrow larger. One testicle usually hangs lower than the other. This is normal.
-
*Sometimes boys breasts become very tender and grow a little. This is normal and will go away in a year or so
-
* Voice gets deeper.
GIRLS
Between the ages of 9 and 16, girls’ bodies begin these changes:
-
*Hips broaden.
-
* Waist narrows.
-
*Hair grows under arms and around vulva and vagina (pubic area).
-
*Vagina, vulva and clitoris grow slightly.
-
*Breasts grow and develop. Sometimes one breast grows larger than the other. This is normal.
-
*Vagina discharges white, sticky substance. This is the vagina’s way of cleaning itself and is normal.
The body actually has two different coordination systems. One of them is the nervous system—the train, the spinal cord, and the network of nerves that runs through all parts of the body. The nervous system carries messages rapidly, somewhat like the network of telephone wires that criss-crosses a city. The other coordination system, the endocrine system, carries messages more slowly. For it takes longer for chemicals to be manufactured and carried through the bloodstream than it does for an electrical message to flash along as nerve. In this way, then, the endocrine system is more like the postal system of a city; letters take much longer to arrive than telephone calls, but they frequently carry very important information.
Often the body’s two coordination systems work together. Messages sent along nerves may stimulate a gland to begin producing hormones. Or hormones may be carried to the brain or nerves and stimulate them to send out messages of their own. Adrenalin makes your heart beat faster and your hair stand on end when you are frightened. But at the same time, messages sent along certain nerves are helping produce the same affects and are also helping to stimulate your glands to make more adrenalin. Thus, both the nervous system and the endocrine system cooperate to help prepare your body for an emergency.
Tiny amounts of powerful drugs called hormones are manufactured daily inside your body. The chemical factories which do this are the endocrine glands. This name means “glands of internal secretion.” They include the thyroid gland, the pituitary gland, the adrenal glands, and others.