The group of organs known as the endocrine glands releases chemical messangers called hormones directly into your bloodstream. These hormones control your body's development and many of its daily activities.

Contributed by: Krista <clayhome@unalink.com>
Country:
Age: 13
Tuesday, October 22, 2002 at 22:24:05 (EDT)

i'm doing a research paper on the endocrine system if there is anyway someone can send me pictures i would grately appreciate it. thanks

Contributed by: Tiffanie <santiago101030@migente.com>
Country: CT
Age: 18
Tuesday, May 28, 2002 at 08:50:44 (EDT)

hello

Contributed by: wew <ewe>
Country: wew
Age: 23
Monday, May 20, 2002 at 13:19:04 (EDT)

IT HAS FACINATING PICTURES AND A LOT OF INFORMATION TO COUNT ON.

Contributed by: Ashley <Hanshaw>
Country: United States of America
Age: 15
Saturday, May 18, 2002 at 12:12:11 (EDT)

The Edocrine system along with the exocrine system makes boobies grow!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Contributed by: Bin laden's bitch <cxgfxhrkehdfej>
Country: fghfghfg
Age: 5
Monday, April 29, 2002 at 12:50:53 (EDT)

Could you please send me information and pictures on the endocrine system that i could teach and use for my class. They are grade 5/6 students. I need this a.s.a.p. It would be very much appreciated.

Contributed by: Julie <jkatis@hotmail.com>
Country: Australia
Age: 23
Friday, April 12, 2002 at 11:22:46 (EDT)

ineed some pictures of the endocrine system and all the information i can get for nursing school.

Contributed by: peggy landry <peggybreaux@bellsouth>
Country: usa
Age: 39
Friday, March 15, 2002 at 00:20:08 (EST)

Hi. I am doing a project and we have to find out the disesses and disunctions of our system. I got chosen for endocrine. I am having slight trouble finding these two topics. I also need to know what the disease are meaning what do they mean. If you can find this infoa nd send it to me, that would be great. I will really appreciate it. Thanks z whole lot.

Contributed by: Chandani Daswani <mooonlite14@aol.com>
Country: USA
Age: 11
Monday, March 04, 2002 at 18:33:38 (EST)

can you please send me some infop on what the important parts of the endocrine system and how they work together to make the system work?? can you also send me some information on possible complications/ problems that could occur if this sytem malfunctioned? and also information on what harms this sytem and what helps this sytem. thank you very much. ~Bree

Contributed by: bree <lacrossegurl882@aol.com>
Country: usa
Age: 13
Monday, February 25, 2002 at 10:16:50 (EST)

Hey i need any information on the Dndocrine System so if you have any please email me thanks for a speech due the 5th of March!!!

Contributed by: ________ <ange91988@hotmail.com>
Country: U.S.A
Age: _________
Saturday, February 23, 2002 at 22:04:50 (EST)

if you can e-mail me some pictues of the Endocrine System i would be very glad. I need them for my class project and no one has them.

Contributed by: Mathew Kleppin <s7767722@mail.milwaukee.k12.wi.us>
Country: U.S.A
Age: 12
Tuesday, February 05, 2002 at 15:50:38 (EST)

i need pictures

Contributed by: Mathew Kleppin <s7767722@mail.milwaukee.k12.wi.us>
Country: U.S.A
Age: 12
Tuesday, February 05, 2002 at 15:49:43 (EST)

I need few pictures and what it is about if one of you people can send me information I will be gled. Tank you

Contributed by: EC <karasevdaliyim3@hotmail.com>
Country: United States
Age: 15
Wednesday, January 16, 2002 at 09:42:37 (EST)

Eduardo id a 30 year old man who has been fighting with his girlfriend for 3 years.He has just had lunch with her .Eduardo ate turkey sandwich,later Eduardo is feeling tired and his stomach is cramping. Eduardo's stomach continues to hurt until he takes some Pepto bismol a couple of hours later. [I have to illustrate on the poster the sequence of events involving the four body systems mentioned above that occurred in order for Eduardo to digest the sandwich he ate during lunch.Include the glands[endocrine /exocrine] and organs involved in digestion and excretion, as well as the cardiovascular vessels adn structures[the heart] that interact with these systems] I have found that stomach egg was caused by stress,but I can't explain how pepto bismal cure stomach-egg.And I know that when you get stress, blood pressure rises,but does it relate to heart?And I know adrenal gland cause you to stress. please sent me email until 19th

Contributed by: koji ito <itohou>
Country: America
Age: 14
Monday, April 16, 2001 at 21:00:22 (EDT)

Eduardo id a 30 year old man who has been fighting with his girlfriend for 3 years.He has just had lunch with her .Eduardo ate turkey sandwich,later Eduardo is feeling tired and his stomach is cramping. Eduardo's stomach continues to hurt until he takes some Pepto bismol a couple of hours later. [I have to illustrate on the poster the sequence of events involving the four body systems mentioned above that occurred in order for Eduardo to digest the sandwich he ate during lunch.Include the glands[endocrine /exocrine] and organs involved in digestion and excretion, as well as the cardiovascular vessels adn structures[the heart] that interact with these systems] I have found that stomach egg was caused by stress,but I can't explain how pepto bismal cure stomach-egg.And I know that when you get stress, blood pressure rises,but does it relate to heart?And I know adrenal gland cause you to stress. please sent me email until 19th

Contributed by: koji ito <itohou>
Country: America
Age: 14
Monday, April 16, 2001 at 20:58:59 (EDT)

Anyone have any great info and/or resources with regard to cortisol? Thanks!

Contributed by: Nancy <nl1954@aol.com>
Country: US
Age: 47
Monday, April 16, 2001 at 02:23:03 (EDT)

acdefghijklmnopqrstuvwxy and z ABCDEFGHIJKLMNOPQSTUVWXY AND Z Well people, that's all for todays lesson over the endocrine system 'til tomorrow

Contributed by: Michael Hucks <m_hucks22@hotmail.com>
Country: USA
Age: 13
Tuesday, April 10, 2001 at 11:46:26 (EDT)

If anyone has a short, concise review of the endocrine system, something around 5 pages or so would be appreciated greatly. So if anyone has anything like this, please e-mail me. It's needed for my Anatomy and Physiology class. Thanks

Contributed by: Matt <Dapimpmastermatt@aol.com>
Country: USA
Age: 18
Monday, April 09, 2001 at 14:36:31 (EDT)

Okay, so we know so much about the endocrine system, how about who discovered it and how to research it? What sort of tests do they pull? I'm talking specifically about the thyroid-- I'm doing a project on it.

Contributed by: William Hampton <Dhenrhode@Hotmail.com>
Country: United States
Age: 13
Tuesday, April 03, 2001 at 08:08:50 (EDT)

I need pictures of the Endocrine system please.

Contributed by: Jeremy D. Smiley <EZskidz@msn.com>
Country: UNITED STATES of AMERICA
Age: 12
Saturday, March 31, 2001 at 23:25:20 (EST)

i have a concept i i have to do for my a&p class of the endocrine system any suggestions or examples of ones for this system pleasse e mail thanks heather

Contributed by: heather <hebdonjr@eaarthlink.net>
Country: usa
Age: 29
Monday, March 26, 2001 at 22:22:12 (EST)

We need individual pictures of the various glands in the Endocrine System. 1. thryoid gland 2. Gonads 3. Pituitary Gland 4. Pancreas 5. Adrenal Glands 6. Parathyroid Glands

Contributed by: Nicole and Tiara <kdillon@ccsc.k12.in.us>
Country: United States
Age: 15
Monday, March 05, 2001 at 13:39:20 (EST)

Ditto

Contributed by: Chris
Country:
Age:
Wednesday, February 28, 2001 at 10:47:16 (EST)

I'm doing a project about the endocrine system and wondering if you can give me some informations about that system with pictures. It's would be thankful and helpful for me and my partner, Andrew to do our project well. Thank you, Jiyeon from Japan For Canadian Academy International School.

Contributed by: Jiyeon Kim <queenofpop7@hotmail.com>
Country: Japan
Age: 14
Sunday, February 25, 2001 at 06:43:49 (EST)

the endocrine system is basically a system that does stuff ;)

Contributed by: Gina <Gina@mail.com>
Country: Phillipines
Age: 14
Sunday, February 25, 2001 at 04:08:10 (EST)

I need to know more about the endocrine system.

Contributed by: Kevin Olivares <redzand2008@hotmail.com>
Country: USA
Age: 12
Monday, February 05, 2001 at 23:10:01 (EST)

i need a picture of the whole part of the endocrine system!!please help me find the best picture of the endocrine system please!!

Contributed by: Mikella Thompson <shortstuff_m@hotmail.com>
Country: United States
Age: 10
Tuesday, January 23, 2001 at 20:28:21 (EST)

I want find the structure and function and enocrine regulation .

Contributed by: sajana <scu112@hotmail.com>
Country: sri-lanka
Age: 21
Friday, December 15, 2000 at 10:53:02 (EST)

what?

Contributed by: nine <19>
Country: mecca
Age: 19
Thursday, December 14, 2000 at 11:35:05 (EST)

pppppppppppppppppppppppppppppppppppppppppppppok h

Contributed by: 98450345 <poiuykngfh@hgdcv gm.com>
Country: p[po,
Age: 99
Friday, October 27, 2000 at 17:44:43 (EDT)

----.......--TheEndocrine System One of the most powerful, if not the most powerful, group of chemicals in the body which affect every aspect of its functioning from reproduction to the maintenance of health, are organic compounds collectively referred to as hormones. The term hormone, which is derived from Greek meaning "set in motion" or "excite", was first used in 1902 to describe secretin, a substance secreted by the duodenum which stimulates pancreatic secretion. Hormones are potent substances in that very minute amounts can effect marked bodily changes. For instance, the injection of 0.001 mg (milligram) of epinephrine or adrenalin into a cat can produce significant effects on the heart and blood vessels. The rates of secretion of hormones are measured in micrograms (a microgram being one millionth of a gram) or milligrams (a milligram being one thousandth of a gram). Depending on their chemical structure, hormones are classified under one of two general groups: (a) steroids which have a chemical structure similar to that of cholesterol; (b) nitrogen compounds such as amines, amino acids, polypeptides and proteins. The glands responsible for the production and release of hormones into the body comprise the endocrine system. Scattered throughout the body, there are nine principal endocrine glands: the pituitary (the master gland), the adrenals (the stress glands), the thyroid and parathyroids (the metabolism glands), the testes and ovaries (the sex glands or gonads), the placenta (the pregnancy gland), the islets of Langerhans in the pancreas (the insulin gland), and the thymus (the immune gland). In addition, the pineal, having been called in the past "the seat of the soul", is traditionally considered a principal endocrine gland but the current knowledge of its function in humans is unclear. Furthermore endocrine activities have been identified in certain organs, such as the heart, kidneys, duodenum and liver, which are normally associated with other system functions. The endocrine glands are ductless and secrete hormones directly into the blood or lymph. They are differentiated from the exocrine glands, such as the salivary or sweat glands, that secrete their products through ducts which open onto a surface. The pituitary gland, also called hypophysis cerebri, is found at the base of the brain and connected to the hypothalamus by the hypophysial stalk. The pituitary consists of an anterior lobe and a posterior lobe --each lobe secreting different hormones. The pituitary is considered the master gland because its hormones, either directly or indirectly, affect the functioning of the entire endocrine system. Because the pituitary is located in the brain and has both neural and humoral (blood) connections to the hypothalamus, it is also the endocrine gland traditionally associated with cognitive control. However it is now known that a number of endocrine glands receive direct neural input via the autonomic nervous system and respond to that neural input in concert with the hormonal secretions of the pituitary. The pituitary, through a series of hormonal feedback loops, acts as the principal regulator of these responses. However this regulation can be overridden via input from the neurologic system. The hormones secreted by the two lobes of the pituitary are specific and clearly differentiated in function. The anterior lobe secretes a number of hormones, one of which is growth hormone (somatotropin) that is associated with the development of cells and tissues in the body. A lack or overproduction of growth hormone accounts for dwarfism and giantism respectively. An anterior pituitary hormone that has recently received much attention due to its role in the stress response is the adrenocorticotrophic hormone (ACTH). Stress stimulates the production of ACTH which, in turn, stimulates the adrenal cortex to secrete gluco-corticoids and mineralo- corticoids. The anterior lobe of the pituitary also secretes thyroid-stimulating hormone (TSH) which causes the thyroid gland to secrete thyroxine and triidothyronine -- a lack of which results in sluggishness. In addition, the anterior pituitary secretes gonad-stimulating hormones or gonadotropins: the follicle-stimulating hormone, which promotes the formation of sperm in the testes (in males) or stimulates growth of follicles in the ovaries before ovulation (in females); the luteinizing hormone, which affects the production of testosterone by the testes or estrogen by the ovaries; and, prolactin, which promotes breast development and milk secretion. On the other hand, the posterior lobe of the pituitary secretes oxytocin which contracts the uterus during the birthing process as well as expels milk during breast-feeding. Another well-known posterior pituitary hormone is vasopressin which contracts arterial walls throughout the body, thereby elevating blood pressure. Additionally vasopressin affects water retention by the kidneys. The adrenal glands are two encapsulated, flattened bodies lying above the kidneys. Each adrenal gland consists of an external cortical portion (cortex) and an inner medullary portion (medulla). The adrenal cortex secretes two groups of hormones: (a) gluco-corticoids, including cortisone and cortisol (also called anti-inflammatory corticoids), which primarily affect protein and carbohydrate metabolism; and, (b) mineralo-corticoids, including deoxycorticosterone and aldosterone (also called pro-inflammatory corticoids), which influence electrolyte balance and water distribution in the tissues. There is growing recognition of the role of these corticoids in decreasing immunological efficiency as a function of chronic or sustained stress. The adrenal medulla secretes two hormones, adrenalin (also called epinephrine) and noradrenalin (also called norepinephrine). These hormones have similar effects in that they stimulate the heart, induce vasoconstriction, increase the rate of carbohydrate metabolism, and increase irritability of the central nervous system. The adrenal medulla is initially activated by stress signals from sympathetic innervations. The medulla then releases adrenalin and noradrenalin into the bloodstream throughout the body. Their release coupled with hypothalamic signals activates the pituitary, bringing its hormones into play. The thyroid gland, which is a bilobed structure anterior to the upper part of the trachea, regulates basal metabolism through its hormones, thyroxine and triidothyronine. The thyroid also secretes calcitonin which influences bone ossification. The parathyroid glands are usually four in number and lie behind the thyroid gland. Their secretion is called parathormone which influences the metabolism of calcium and phosphorous. After birth, the gonads are dormant until puberty when they are activated by gonadotropins from the anterior pituitary. The gonads secrete hormones for reproductive functions. In the female, the major hormones associated with the ovaries are estrogen and progesterone. Estrogen stimulates the development of the female sex organs, breasts and secondary sexual characteristics as well as regulates the sexual cycles. Progesterone prepares the uterus for pregnancy and helps develop the secretory apparatus of the breasts. The ovarian functions decline after a period of time and the sexual cycles eventually cease (menopause). The gonads in males remain more or less active from puberty onward. The testes secrete testosterone which stimulates growth of the male sex organs and development of male secondary sexual characteristics. The placenta develops in the pregnant female during the first week of pregnancy when the blastocyst (developing embryo) implants itself into the wall of the uterus. The placenta secretes at least five hormones: (1) human chorionic gonadotropin (hCG), a glycoprotein that contains lactose; (2) human chorionic somatomammotropin (hCS), a protein hormone that is lactogenic and has a small amount of growth stimulating activity; (3) progesterone; (4) estrogen; and, (5) relaxin which relaxes the pubic ligaments at the time of delivery. The placenta also contains two beta-endorphin-like materials, the significance of which is presently unknown. The pancreas is a double-functioning gland. It produces an exocrine secretion which is discharged into the duodenum. It likewise produces an endocrine secretion which is discharged into the bloodstream. The endocrine portion of the pancreas consists of the islets of Langerhans which lie scattered throughout the pancreas. The principal hormones secreted by the islets of Langerhans are insulin and glucagon. These two hormones have reciprocal actions in regulating the utilization of glucose by the tissue cells, glycogen formation in the liver, and conversion of glycogen into glucose. The human thymus gland is a flat, bilobed organ located below the thyroid along the neck and extending into the thoracic cage. Anatomically the thymus is a pouch of epithelial cells filled with lymphocytes (thymic or T- lymphocytes) nourished and drained by the vascular and lymphatic systems. Until recently, the thymus was considered merely a lymphoid organ. The dispute over the thymus as an endocrine organ was resolved upon identification of a family of peptides that control the proliferation and maturation of primitive lymphocytes into immunologically competent T-cells. However it is apparent from some medical textbooks that significant resistance remains in accepting the thymus as a vital endocrine gland. Nonetheless there is ample evidence that the thymus is a master gland in the development and differentiation of T-leukocytes. It is now known that the epithelial cells of the thymus synthesize at least 30 different polypeptides or thymic hormones. Although much more research needs to be done, the chemical structure of some of these hormones has been identified. Thymosin is a mixture of 15 or more proteins. One of these proteins is thymosin alpha-1 which consists of 28 amino acids. Thymopoietin is the largest of the known thymic hormones and consists of 49 amino acids. Thymic humoral factor has 31 amino acids. On the other hand, thymulin (previously known as thymic serum factor) is the smallest of the chemically characterized thymic hormones and consists of 9 amino acids. The thymus begins to involute, decreasing in size and weight, during puberty. Yet the thymus generally continues to be active and produces lymphocytes throughout life. However, in the course of time, the body becomes increasingly vulnerable to illnesses and chronic diseases. Differences in thymic secretions have been found between normal (illness- free) individuals and those with immune disorders. The pineal gland, also called epiphysis, is a conical body that extends from the roof of the third ventricle under the posterior end of the corpus callosum in the brain. This gland begins to involute before puberty. Furthermore, in humans, small concretions of calcium phosphate and carbonate appear in the tissue. The pineal secretes melatonin which appears to show diurnal variations. Melatonin synthesis and secretion increase during the dark period of the day and are maintained at a low level during daylight. It is speculated that this diurnal variation in melatonin secretion, rather than melatonin itself, serves as a timing device. It has also been said that the pineal gland inhibits the onset of puberty in humans. So far the best conclusion is that the exact function of the pineal gland and melatonin in humans is obscure. In addition to the principal endocrine glands, there are other bodily organs with endocrine functions. The heart produces at least one hormone, called atrial natriuretic peptide (ANP), which increases the excretion of sodium by the kidneys. ANP also inhibits vasopressin and lowers blood pressure. The kidneys produce three hormones which include renin, a glycoprotein hormone involved with the maintenance of blood pressure. ANP is known to inhibit renin secretion. The mucosa of the gastrointestinal tract secretes a number of hormones and peptides into the body. Among them are gastrin, chotecystokinin-pancreozymin (CCK), secretin, gastric inhibitory peptide (GIP), glicentin (GLI), vasoactive intestinal polypeptide (VIP), motilin, somatostatin, glucagon, urogastrone, and pancreatic polypeptide. Although substance P is also found in endocrine cells of the gastrointestinal tract, it has not been proved to enter the circulation. The liver, on the other hand, is the principal site of the chemical breakdown of glucocorticoids (steroid hormones). Cortisol, for example, is metabolized by the liver and then excreted in the urine or stool. The rate of hepatic inactivation of glucocorticoids is depressed in liver disease and, interestingly, during surgery and other stresses. The liver also inactivates some polypeptide hormones as well. As a final note, remembering the definition of an endocrine organ, the hypothalamus secretes hormones that stimulate, or inhibit, secretions of the anterior pituitary. Indeed the hypothalamus is an excellent example of the blurring of functions as well as the interactions between the three major physiologic systems of the human body (the endocrine, the neurologic and the immune). Anatomically, the hypothalamus is part of the brain. It is located beneath the thalamus in the diencephalon. Neuro-electrical signals from the limbic system (read the chapter on the neurologic system) are the primary neural trigger for the hypothalamus. In turn, neuro-electrical signals from the hypothalamus trigger both the sympathetic and the parasympathetic branches of the autonomic nervous system as well as the posterior pituitary. On the other hand, the hypothalamus also produces a variety of hormones. Among them are gonadotropin releasing hormone, growth hormone releasing hormone, growth hormone inhibiting hormone also known as somatostatin, TSH releasing hormone, prolactin inhibiting hormone, and corticotropin releasing hormone. These hormones are conveyed through a group of blood vessels, known as the portal system, to the anterior pituitary triggering the release, or inhibition, of the corresponding pituitary hormones. Furthermore the hypothalamus is an integral part of a series of feedback loops which, not only regulate many systemic physiologic processes, but also adjust those processes to deal with environmental or internal changes and/or threats to the organism --be they real or perceived. As part of this feedback system, the hypothalamus senses the amount of certain hormones in the blood like ACTH or cortisol, the amount of neural stimulation in the limbic system, and, as recently discovered, the amount of certain thymic hormones such as thymosin fraction 5 in the blood. This information is then processed by the hypothalamus and adjustments in both neural and hormonal secretions are accomplished. The adjustment can be either to restore homeostasis or to move in either direction from it, depending upon the result of the combined information processed by the hypothalamus. Chapter from The Body Immortal by J. F. Ripka & F. T. Ripka (1995) Top of Page......_ BioSyn site copyright 1996 by James F. Ripka.

Contributed by: andy gallagher <andrewgallagher@hotmail.com>
Country: Ireland
Age: 18
Monday, September 25, 2000 at 13:21:04 (EDT)

----.......--TheEndocrine System One of the most powerful, if not the most powerful, group of chemicals in the body which affect every aspect of its functioning from reproduction to the maintenance of health, are organic compounds collectively referred to as hormones. The term hormone, which is derived from Greek meaning "set in motion" or "excite", was first used in 1902 to describe secretin, a substance secreted by the duodenum which stimulates pancreatic secretion. Hormones are potent substances in that very minute amounts can effect marked bodily changes. For instance, the injection of 0.001 mg (milligram) of epinephrine or adrenalin into a cat can produce significant effects on the heart and blood vessels. The rates of secretion of hormones are measured in micrograms (a microgram being one millionth of a gram) or milligrams (a milligram being one thousandth of a gram). Depending on their chemical structure, hormones are classified under one of two general groups: (a) steroids which have a chemical structure similar to that of cholesterol; (b) nitrogen compounds such as amines, amino acids, polypeptides and proteins. The glands responsible for the production and release of hormones into the body comprise the endocrine system. Scattered throughout the body, there are nine principal endocrine glands: the pituitary (the master gland), the adrenals (the stress glands), the thyroid and parathyroids (the metabolism glands), the testes and ovaries (the sex glands or gonads), the placenta (the pregnancy gland), the islets of Langerhans in the pancreas (the insulin gland), and the thymus (the immune gland). In addition, the pineal, having been called in the past "the seat of the soul", is traditionally considered a principal endocrine gland but the current knowledge of its function in humans is unclear. Furthermore endocrine activities have been identified in certain organs, such as the heart, kidneys, duodenum and liver, which are normally associated with other system functions. The endocrine glands are ductless and secrete hormones directly into the blood or lymph. They are differentiated from the exocrine glands, such as the salivary or sweat glands, that secrete their products through ducts which open onto a surface. The pituitary gland, also called hypophysis cerebri, is found at the base of the brain and connected to the hypothalamus by the hypophysial stalk. The pituitary consists of an anterior lobe and a posterior lobe --each lobe secreting different hormones. The pituitary is considered the master gland because its hormones, either directly or indirectly, affect the functioning of the entire endocrine system. Because the pituitary is located in the brain and has both neural and humoral (blood) connections to the hypothalamus, it is also the endocrine gland traditionally associated with cognitive control. However it is now known that a number of endocrine glands receive direct neural input via the autonomic nervous system and respond to that neural input in concert with the hormonal secretions of the pituitary. The pituitary, through a series of hormonal feedback loops, acts as the principal regulator of these responses. However this regulation can be overridden via input from the neurologic system. The hormones secreted by the two lobes of the pituitary are specific and clearly differentiated in function. The anterior lobe secretes a number of hormones, one of which is growth hormone (somatotropin) that is associated with the development of cells and tissues in the body. A lack or overproduction of growth hormone accounts for dwarfism and giantism respectively. An anterior pituitary hormone that has recently received much attention due to its role in the stress response is the adrenocorticotrophic hormone (ACTH). Stress stimulates the production of ACTH which, in turn, stimulates the adrenal cortex to secrete gluco-corticoids and mineralo- corticoids. The anterior lobe of the pituitary also secretes thyroid-stimulating hormone (TSH) which causes the thyroid gland to secrete thyroxine and triidothyronine -- a lack of which results in sluggishness. In addition, the anterior pituitary secretes gonad-stimulating hormones or gonadotropins: the follicle-stimulating hormone, which promotes the formation of sperm in the testes (in males) or stimulates growth of follicles in the ovaries before ovulation (in females); the luteinizing hormone, which affects the production of testosterone by the testes or estrogen by the ovaries; and, prolactin, which promotes breast development and milk secretion. On the other hand, the posterior lobe of the pituitary secretes oxytocin which contracts the uterus during the birthing process as well as expels milk during breast-feeding. Another well-known posterior pituitary hormone is vasopressin which contracts arterial walls throughout the body, thereby elevating blood pressure. Additionally vasopressin affects water retention by the kidneys. The adrenal glands are two encapsulated, flattened bodies lying above the kidneys. Each adrenal gland consists of an external cortical portion (cortex) and an inner medullary portion (medulla). The adrenal cortex secretes two groups of hormones: (a) gluco-corticoids, including cortisone and cortisol (also called anti-inflammatory corticoids), which primarily affect protein and carbohydrate metabolism; and, (b) mineralo-corticoids, including deoxycorticosterone and aldosterone (also called pro-inflammatory corticoids), which influence electrolyte balance and water distribution in the tissues. There is growing recognition of the role of these corticoids in decreasing immunological efficiency as a function of chronic or sustained stress. The adrenal medulla secretes two hormones, adrenalin (also called epinephrine) and noradrenalin (also called norepinephrine). These hormones have similar effects in that they stimulate the heart, induce vasoconstriction, increase the rate of carbohydrate metabolism, and increase irritability of the central nervous system. The adrenal medulla is initially activated by stress signals from sympathetic innervations. The medulla then releases adrenalin and noradrenalin into the bloodstream throughout the body. Their release coupled with hypothalamic signals activates the pituitary, bringing its hormones into play. The thyroid gland, which is a bilobed structure anterior to the upper part of the trachea, regulates basal metabolism through its hormones, thyroxine and triidothyronine. The thyroid also secretes calcitonin which influences bone ossification. The parathyroid glands are usually four in number and lie behind the thyroid gland. Their secretion is called parathormone which influences the metabolism of calcium and phosphorous. After birth, the gonads are dormant until puberty when they are activated by gonadotropins from the anterior pituitary. The gonads secrete hormones for reproductive functions. In the female, the major hormones associated with the ovaries are estrogen and progesterone. Estrogen stimulates the development of the female sex organs, breasts and secondary sexual characteristics as well as regulates the sexual cycles. Progesterone prepares the uterus for pregnancy and helps develop the secretory apparatus of the breasts. The ovarian functions decline after a period of time and the sexual cycles eventually cease (menopause). The gonads in males remain more or less active from puberty onward. The testes secrete testosterone which stimulates growth of the male sex organs and development of male secondary sexual characteristics. The placenta develops in the pregnant female during the first week of pregnancy when the blastocyst (developing embryo) implants itself into the wall of the uterus. The placenta secretes at least five hormones: (1) human chorionic gonadotropin (hCG), a glycoprotein that contains lactose; (2) human chorionic somatomammotropin (hCS), a protein hormone that is lactogenic and has a small amount of growth stimulating activity; (3) progesterone; (4) estrogen; and, (5) relaxin which relaxes the pubic ligaments at the time of delivery. The placenta also contains two beta-endorphin-like materials, the significance of which is presently unknown. The pancreas is a double-functioning gland. It produces an exocrine secretion which is discharged into the duodenum. It likewise produces an endocrine secretion which is discharged into the bloodstream. The endocrine portion of the pancreas consists of the islets of Langerhans which lie scattered throughout the pancreas. The principal hormones secreted by the islets of Langerhans are insulin and glucagon. These two hormones have reciprocal actions in regulating the utilization of glucose by the tissue cells, glycogen formation in the liver, and conversion of glycogen into glucose. The human thymus gland is a flat, bilobed organ located below the thyroid along the neck and extending into the thoracic cage. Anatomically the thymus is a pouch of epithelial cells filled with lymphocytes (thymic or T- lymphocytes) nourished and drained by the vascular and lymphatic systems. Until recently, the thymus was considered merely a lymphoid organ. The dispute over the thymus as an endocrine organ was resolved upon identification of a family of peptides that control the proliferation and maturation of primitive lymphocytes into immunologically competent T-cells. However it is apparent from some medical textbooks that significant resistance remains in accepting the thymus as a vital endocrine gland. Nonetheless there is ample evidence that the thymus is a master gland in the development and differentiation of T-leukocytes. It is now known that the epithelial cells of the thymus synthesize at least 30 different polypeptides or thymic hormones. Although much more research needs to be done, the chemical structure of some of these hormones has been identified. Thymosin is a mixture of 15 or more proteins. One of these proteins is thymosin alpha-1 which consists of 28 amino acids. Thymopoietin is the largest of the known thymic hormones and consists of 49 amino acids. Thymic humoral factor has 31 amino acids. On the other hand, thymulin (previously known as thymic serum factor) is the smallest of the chemically characterized thymic hormones and consists of 9 amino acids. The thymus begins to involute, decreasing in size and weight, during puberty. Yet the thymus generally continues to be active and produces lymphocytes throughout life. However, in the course of time, the body becomes increasingly vulnerable to illnesses and chronic diseases. Differences in thymic secretions have been found between normal (illness- free) individuals and those with immune disorders. The pineal gland, also called epiphysis, is a conical body that extends from the roof of the third ventricle under the posterior end of the corpus callosum in the brain. This gland begins to involute before puberty. Furthermore, in humans, small concretions of calcium phosphate and carbonate appear in the tissue. The pineal secretes melatonin which appears to show diurnal variations. Melatonin synthesis and secretion increase during the dark period of the day and are maintained at a low level during daylight. It is speculated that this diurnal variation in melatonin secretion, rather than melatonin itself, serves as a timing device. It has also been said that the pineal gland inhibits the onset of puberty in humans. So far the best conclusion is that the exact function of the pineal gland and melatonin in humans is obscure. In addition to the principal endocrine glands, there are other bodily organs with endocrine functions. The heart produces at least one hormone, called atrial natriuretic peptide (ANP), which increases the excretion of sodium by the kidneys. ANP also inhibits vasopressin and lowers blood pressure. The kidneys produce three hormones which include renin, a glycoprotein hormone involved with the maintenance of blood pressure. ANP is known to inhibit renin secretion. The mucosa of the gastrointestinal tract secretes a number of hormones and peptides into the body. Among them are gastrin, chotecystokinin-pancreozymin (CCK), secretin, gastric inhibitory peptide (GIP), glicentin (GLI), vasoactive intestinal polypeptide (VIP), motilin, somatostatin, glucagon, urogastrone, and pancreatic polypeptide. Although substance P is also found in endocrine cells of the gastrointestinal tract, it has not been proved to enter the circulation. The liver, on the other hand, is the principal site of the chemical breakdown of glucocorticoids (steroid hormones). Cortisol, for example, is metabolized by the liver and then excreted in the urine or stool. The rate of hepatic inactivation of glucocorticoids is depressed in liver disease and, interestingly, during surgery and other stresses. The liver also inactivates some polypeptide hormones as well. As a final note, remembering the definition of an endocrine organ, the hypothalamus secretes hormones that stimulate, or inhibit, secretions of the anterior pituitary. Indeed the hypothalamus is an excellent example of the blurring of functions as well as the interactions between the three major physiologic systems of the human body (the endocrine, the neurologic and the immune). Anatomically, the hypothalamus is part of the brain. It is located beneath the thalamus in the diencephalon. Neuro-electrical signals from the limbic system (read the chapter on the neurologic system) are the primary neural trigger for the hypothalamus. In turn, neuro-electrical signals from the hypothalamus trigger both the sympathetic and the parasympathetic branches of the autonomic nervous system as well as the posterior pituitary. On the other hand, the hypothalamus also produces a variety of hormones. Among them are gonadotropin releasing hormone, growth hormone releasing hormone, growth hormone inhibiting hormone also known as somatostatin, TSH releasing hormone, prolactin inhibiting hormone, and corticotropin releasing hormone. These hormones are conveyed through a group of blood vessels, known as the portal system, to the anterior pituitary triggering the release, or inhibition, of the corresponding pituitary hormones. Furthermore the hypothalamus is an integral part of a series of feedback loops which, not only regulate many systemic physiologic processes, but also adjust those processes to deal with environmental or internal changes and/or threats to the organism --be they real or perceived. As part of this feedback system, the hypothalamus senses the amount of certain hormones in the blood like ACTH or cortisol, the amount of neural stimulation in the limbic system, and, as recently discovered, the amount of certain thymic hormones such as thymosin fraction 5 in the blood. This information is then processed by the hypothalamus and adjustments in both neural and hormonal secretions are accomplished. The adjustment can be either to restore homeostasis or to move in either direction from it, depending upon the result of the combined information processed by the hypothalamus. Chapter from The Body Immortal by J. F. Ripka & F. T. Ripka (1995) Top of Page......_ BioSyn site copyright 1996 by James F. Ripka.

Contributed by: 0andy
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Monday, September 25, 2000 at 13:19:56 (EDT)

For those of you interested the endocrine system basically is the control system for the body. The glands and the hormones that they produce inform the body about the following:when to produce materials to assist in building your immune system,when to start maturing the body for adulthood, controls the metabolism of food, your ability to fight or flight, reproduction, the clacium levels of the blood and most of the feedback mechanisms that allow the body to maintain itself in a constant state. Does that help anyone?