The Human Body - Endocrine System (1980)

[Music] thank you [Music] all of your body's basic internal activities are coordinated by the glands of your endocrine system coordination is necessary whenever different parts of the system have to work together to achieve a common goal when you move for instance you have to coordinate the separate movements of your arms and legs you control the contraction and relaxation of many muscles all over your body out of these many small separate movements comes a unified action that allows your whole body to move efficiently coordination a working together now inside your body there are trillions of cells their activities have to be coordinated too these tiny bits of Life have to work together properly for you to stay healthy and alive but you don't have any conscious control over this coordination coordinating the activities of your body's cells is the function of your endocrine system a group of glands in various parts of your body that have very specific jobs an endocrine gland is a group of specialized cells that produce very powerful chemicals called hormones a gland is usually composed of several kinds of cells each of these different kinds of cells produces a different hormone when hormones are released or secreted by a gland they pass directly into your bloodstream the endocrine glands have no ducts as other glands do but they are richly supplied with blood vessels it's because they are without ducks that the endocrine glands are called ductless so carried by your circulating blood hormones from the different glands come in contact with your body's cells now each hormone has a very specific chemical structure structure is very important in the work the hormones do it allows them to react with only certain groups of cells in your body these cells are called target cells when hormones reach their target cells the life functions of all these cells are affected in the same specific way some functions may speed up some functions may slow down but all these target cells make these changes in their activities together this is how hormones of your endocrine glands coordinate your body's basic internal activities now let's see some of the ways hormones control and regulate your body's activities one of the most dramatic changes that takes place in you is your body's growth from the time you're nearly microscopic in size and your cells are First beginning to differentiate until the time when you've reached your maximum growth your body has increased its size by many millions of times this vast change in your body is controlled by a tiny gland that hangs by a stalk from the base of your brain this is the pituitary gland barely one centimeter in diameter less than half an inch about the size of a pea your growth is only one of the many activities controlled by the pituitary it's actually a kind of Master gland controlling the activities of most of the other glands of your endocrine system the pituitary is really two glands in one parts or lobes are quite different they're composed of different kinds of cells that secrete different kinds of hormones the back part of the pituitary gland the posterior lobe secretes at least two kinds of hormones that we know of these hormones actually aren't manufactured in the gland but in nerve cells in a nearby part of the brain the hormones are stored in the posterior lobe and then released when needed one of these hormones affects smooth muscle tissue in women it causes muscles at the uterus to contract during childbirth the other hormone from the posterior lobe of the pituitary affects the functioning of your kidneys controlling the amount of water they eliminate from your body while cells in the posterior lobe only store and then secrete hormones cells in the anterior or front lobe of the pituitary actually produce the hormones they release the front lobe of the pituitary produces at least seven different hormones that we know of and one of them is the hormone that controls your growth this hormone is called GH the letters simply stand for growth hormone the growth hormone's main target cells are those that make up bone and muscle tissue how much you grow depends on how much of the hormone your pituitary gland produces output of the growth hormone increases as you approach puberty the time when you mature sexually many of the other hormones secreted by the anterior lobe of the pituitary regulate the secretions of other endocrine glands one of these hormones is called the thyroid stimulating hormones TSH the gland that the thyroid stimulating hormone affects of course is the thyroid gland one of several glands that regulate the day-to-day life functions of your cells the thyroid gland is located in your neck just below the larynx your voice box the thyroid is much larger than the pituitary like the pituitary it has two lobes the lobes wrap around your windpipe the thyroid glands secretes several kinds of hormones but the one produced in the greatest amount is thyroxine all the thyroid hormones contain the element iodine and have similar chemical structures when they enter your blood they combine with certain proteins there and in this combined form they reach their target cells all the cells of your body's tissues are target cells for thyroid hormones the amount of thyroid hormones that reaches the cells determines their metabolic rate this is the rate at which chemical reactions take place in the cells the more thyroxine and other thyroid hormones the more active the cells become they break down and build up molecules more rapidly more energy is used and released [Music] but when the amount of thyroid hormones reaching the cells decreases then cellular activity decreases too the amount of hormones secreted by your thyroid is controlled by your pituitary gland through a remarkable feedback mechanism when the amount of thyroxine In The Blood Falls below a certain level a special region in your brain releases chemicals that stimulate the pituitary to secrete more of the thyroid stimulating hormone when this increased amount of TSH reaches the thyroid IT cells begin producing more thyroxine when the thyroxine in the blood rises above a certain level that special region of your brain reduces its production of pituitary stimulating chemicals and the pituitary reduces its output of TSH with less TSH reaching the thyroid gland the gland throws its production of thyroxine feedback mechanisms control the functioning of all endocrine glands not just the thyroid buried in the back part of the thyroid gland are four tiny clusters of cells the smallest endocrine glands in your body these are the parathyroids these glands release the parathyroid hormone pth into your bloodstream this hormone affects the life functions of cells by regulating the metabolism of calcium and phosphorus in your cells and their chemical balance in your blood milk and foods made from milk are important sources of calcium and phosphorus these minerals like all nutrients enter your bloodstream as part of the digestive process the parathyroids activity is regulated by the amount of calcium in your blood another feedback mechanism as the calcium level rises the secretion of pth by the parathyroids is reduced if the calcium level drops then the parathyroids are stimulated to produce more of their hormones parathyroids also control the depositing of calcium in your bones as well as its removal astronauts who spent long periods of time in zero gravity conditions lost calcium from their bones as a result of the action of their parathyroids but once they were back on Earth their parathyroids gradually returned the calcium content of their bones to a normal level another gland involved in regulating the life functions of your cells is part of the tissue that makes up your pancreas the pancreas mainly functions as part of your digestive system it produces digestive enzymes that flow through ducts into the small intestine and help you digest your food but scattered among the cells of the pancreas are about a million little clusters of cells that are quite different from the usual pancreatic cells these clusters form the gland that is called the islets of longer hunts named for the physician who researched their activities like all glands of the endocrine system these eyelids secrete their hormones directly into the blood they don't make use of the pancreatic ducts one of the hormones secreted by this gland is insulin insulin regulates the concentration of sugar in your blood and its use by your cells in your cells the sugar glucose is broken down by the cells as part of their metabolism by controlling the metabolism of glucose insulin keeps the glucose level in your blood from getting too high the more glucose there is the more insulin is produced another hormone from the islets of langerhans has just the opposite effect this hormone glucagon keeps the level of blood glucose from getting too low it slows down the metabolism of glucose working together these two hormones like other hormones produced by your endocrine system regulate the life functions of your cells helping to maintain a constant chemical composition of the fluids that bathe them this steady state is called homeostasis homeostasis is absolutely necessary for your health and your life and is maintained by your endocrine system regardless of your activities usually no matter how much you eat how much exercise you do what stresses you're subjected to your body keeps up this internal steady state stress will sometimes affect a part of your endocrine system fear anger or injury can stimulate the release of hormones from a pair of cap shaped glands at the top of each of your kidneys the adrenals their name comes from their location in Latin adrenus means upon the kidney from adrenis we get adrenal there are two parts to each adrenal gland the parts differ in structure and function the outer part is called the cortex the inner part the medulla the medulla contains only two kinds of cells and these cells produce two similar hormones one of them is adrenaline responding to a stress or danger signal from the brain the medulla of the adrenal gland releases adrenaline into your bloodstream as it flows through your body it rapidly crosses a number of effects the sudden edition of adrenaline causes the liver to release greater amounts of glucose into the blood this provides more food for the cells and makes more energy available for Action from your muscles adrenaline reduces the flow of blood to the internal organs like the stomach and instead crosses it to flow in larger amounts to the muscles your heart beats faster blood pressure Rises and your breathing rate increases but the effects of the adrenaline end quickly when the emergency is over the brain signals the adrenal gland to stop releasing adrenaline into your blood enzymes in your blood then destroy the hormone and you soon return to normal adrenaline may help to preserve your life in emergencies but it isn't as essential to your life as hormones from the adrenal cortex the cortex produces three important classes of hormones hormones from the cortex have a variety of vital functions in your body many more than hormones from the medulla have without the hormones of the adrenal cortex you couldn't survive so the life processes of your cells are constantly being regulated by the various hormones secreted by your endocrine glands and there is one more important rule your endocrine system plays in your life it controls your ability to reproduce your endocrine system controls the changes in your body that are part of your sexual maturing the endocrine glands that produce these changes are the testes in the mail and the ovaries in the female but it's the pituitary gland that controls their activity your pituitary gland produces three hormones that affect sexual development these hormones are produced in small amounts even before you're born but usually between the ages of 10 and 14 in the female and 14 and 16 in the male these secretions increase dramatically and they in turn stimulate secretions from the testes and ovaries their hormones cause the major physical changes that complete your sexual development and make it possible for male and female to reproduce the most important of the male sex hormones is testosterone in the female two kinds of sex hormones are secreted estrogen and progesterone as in the case of the other endocrine glands a feedback mechanism regulates the activity of the pituitary in its stimulation of the testes and ovaries and so your endocrine glands regulate and coordinate the life functions of your cells pituitaries are regulator for many of these glands responding to signals from specialized cells in the brain and to feedback signals from the glands themselves pituitary the thyroid and parathyroid the islets of langerhans the adrenals the testes and the ovaries all are part of your endocrine system the system of ductless glands that release their secretions of powerful hormones into your bloodstream it's a system that regulates the life functions and maintains the chemical balance of the trillions of cells whose life and health your life and health depend on thank you