Endocrine System

Adrenal Glands

The adrenal glands are a pair of glands that secrete hormones directly into the bloodstream. Each gland can be divided into two distinct organs. The outer region secretes hormones which have important effects on the way in which energy is stored and food is used, on chemicals in the blood, and on characteristics such as hairiness and body shape. The smaller, inner region is part of the sympathic nervous system and is the body's first line of defense and response to physical and emotional stresses. The adrenal glands are shaped like the French Emperor Napoleon's hat and, just as Napoleon's three-cornered hat sat on his head, so each gland is perched on each of the kidneys. These glands are about one to two inches in length and weigh only a fraction of an ounce each while secreting more than three dozen hormones. They take instruction from the pituitary glands and have important effects on physical characteristics, development and growth. The adrenal gland has two parts. The cortex, or outer, yellow layer, takes its instructions from the pituitary hormone ACTH. The hormones secreted here are called "steroids" and have three main types: those which control the balance of sodium and potassium in the body; those which raise the level of sugar in the blood; and sex hormones. The inner, reddish brown layer makes two types of hormones and takes all its instructions from the nervous system, producing chemicals which react to fear and anger and are sometimes called "fight or flight" hormones.

Ovaries

The ovaries are a pair of oval or almond-shaped glands which lie on either side of the uterus and just below the opening to the fallopian tubes. In addition to producing eggs or "ova," the ovaries produce female sex hormones called estrogen and progesterone. The ovaries produce a female hormone, called estrogen, and store female sex cells or "ova." The female, unlike the male, does not manufacture the sex cells. A girl baby is born with about 60,000 of these cells, which are contained in sac-like depressions in the ovaries. Each of these cells may have the potential to mature for fertilization, but in actuality, only about 400 ripen during the woman's lifetime. Pregnant and prenatal both come from the same Latin roots. "Prae" means "before" and "nascor" means "to be born". Nascor is also the derivative of nature, innate and native. Only a few years ago, the word, "pregnant" was seldom used in mixed company. Polite society referred to a pregnant woman as "expecting" or "being in the family way."

Pancreas

The pancreas is a long. tapered gland which lies across and behind the stomach. The "head" (the right-hand end which is the broadest part of it) lies within the curve of the duodenum. This gland secretes digestive juices which break down fats, carbohydrates, proteins and acids; it also secretes bicarbonate, which neutralizes stomach acid as it enters the duodenum. Some cells in the pancreas secrete hormones which regulate the level of glucose in the blood. Most of the pancreas consists of tissues which are embedded in "nested" cells. These cells secrete the digestive enzymes into tubes which meet to form the main duct. This duct joins the "cystic" duct (which carries bile from the gallbladder) and forms a small chamber which opens into the duodenum. The cells of the pancreas are surrounded by many blood vessels into which they secrete hormones (glucagon and insulin) into the blood. Insulin regulates the use of glucose into all the body tissues except the brain. If the pancreas fails to produce insulin or secretes it in low quantities, the result is a serious disease called diabetes mellitus. The Greek name "pancreas", meaning "all flesh" or "all meat", is descriptive of the protein composition of this powerful organ which resembles a fish with a large head and a long tail. Inside, the organ's appearance resembles a stalk with clusters of grapes attached to it. The "stalk" is a long duct which runs down the center of the pancreas and the "grapes" are clusters of cells which flow into this duct and later into the duodenum for digestion of proteins, fats and carbohydrates. If the ducts leading from the pancreas are blocked in some way, the digestive fluids build up in the pancreas and may then become activated so that they digest the pancreas itself! This condition is known as acute pancreatitis. Pancreatic cancer has the worst prognosis of all the types of cancer. This is probably because of the spongy, vascular nature of this organ and its vital endocrine and exocrine functions. Pancreatic surgery is a problem because of the soft, spongy, tissue it consists of that make it extremely difficult to suture. By the way, Webster's Dictionary says the "pancratium" was an ancient Greek athletic contest involving boxing and wrestling. Isn't that interesting?

Pituitary Gland

The pituitary gland, which is located in the center of the skull, just behind the bridge of the nose, is about the size of a pea. It is an important link between the nervous system and the endocrine system and releases many hormones which affect growth, sexual development, metabolism and the system of reproduction. The "hypothalamus" is a tiny cluster of brain cells just above the pituitary gland, which transmits messages from the body to the brain. The pituitary gland has two distinct parts, the anterior and the posterior lobes, each of which releases different hormones which affect bone growth and regulate activity in other glands. This gland was once believed to be the main controlling gland of the body, but we now know that, important as it is, it is subservient to a master gland called the hypothalamus, which is the needed link between the pituitary gland and the brain. This "master gland" is really a way station between the body and the brain and sorts out messages going to and from the brain. It responds to the body through the pituitary gland, which is suspended just below it. It sometimes replies by nerve impulses and sometimes with needed hormones. The pituitary gland then makes hormones of its own in answer to the body's needs. These are then circulated in the blood to a variety of the body's tissues, including other endocrines, such as the adrenal gland. The adrenal gland receives the hormones produced by the pituitary and produces more of its own in response to growth and development requirements as well as the "fight or flight" responses. By the way, being a dwarf or midget will not hold one back from fame and fortune. Jeffery Hudson, a midget who lived from 1619 to 1682, was given to Queen Henrietta Maria of England by the Duke of Buckingham as a child. He escaped to France with the queen, fought a duel on horseback and won, fled France and was taken by Moorish pirates. He escaped and returned to England. He was eighteen inches tall when he was eight years old (at the time he was given to the queen) and three feet, nine inches in height when he was fully grown. His escapades and daring ought to stimulate us all!

Testicles

The scrotum is a sac that hangs under the penis and holds the testes. It is divided internally into two halves by a membrane; each half containing a testis. It has an outer layer of thin, wrinkled skin over a layer of tissue which contains muscle. The testicle lies inside the scrotum and produces as many as 12 trillion sperm in a male's lifetime, about 400 million of which are ejaculated in one average intercourse. Each sperm takes about seventy-two days to mature and its maturity is overseen by a complex interaction of hormones. The scrotum has a built-in thermostat, which keeps the sperm at the correct temperature. It may be surprising that the testicles should lie in such a vulnerable place, outside the body, but it is too hot inside. The sperm production needs a temperature which is three to five degrees below body temperature. If it becomes too cool on the outside, the scrotum will contract to bring the testes closer the body for warmth.

Thymus

The thymus is a gland that forms part of the immune system. It is situated in the upper part of the chest, behind the breastbone, and is made up of two lobes that join in front of the trachea. Each lobe is made of lymphoid tissue, consisting of tightly packed white blood cells and fat. The thymus enlarges from about the 12th week of gestation until puberty, when it begins to shrink. Its function is to transform lymphocytes (white blood cells developed in the bone marrow) into T-cells (cells developed in the thymus). These cells are then transported to various lymph glands, where they play an important part in fighting infections and disease. Swelling of lymph glands and fever are a signal that immune cells are multiplying to fight off invaders of the body: bacteria, fungi, viruses or parasites. Edward Jenner showed his faith in vaccination by injecting his own son with cowpox, therefore immunizing the child against smallpox, a deadly disease at that time in history

Thyroid and Parathyroid Glands

The thyroid gland is shaped like a butterfly and usually weighs less than one ounce. The thyroid cartilage covers the larynx and produces the prominence on the neck known as the "Adam's Apple". The thyroid gland controls the rate at which the body produces energy from nutrients. If the body does not get enough iodine, the thyroid gland cannot produce a proper amount of hormones for this conversion process. The result can be a goiter, an enlargement of the thyroid gland. In some parts of the world, iodine is so scarce that most of the population have goiters. The parathyroid glands are four small oval bodies located on either side of and on the dorsal aspect of the thyroid gland. These glands control the level of calcium in the blood. The thyroid gland secretes hormones which regulate energy, and emotional balance may rely upon its normal functioning. When the rate of production is excessive, the results can be weight loss, nervousness, or even emotional disturbances. If the rate of production is excessively low, a slowing of bodily functions may result. The parathyroid glands, located behind the thyroid, control the blood-calcium level. Calcium is important, not only for bones and teeth, but also for nerve functioning, muscle contractions, blood clotting and glandular secretion. If we don't have enough calcium for these functions, the body will take it from the bones, causing them to easily fracture. It may also cause twitching, spasms, convulsions and even death. Too much calcium may cause a weakening of muscle tone and kidney stones.