2/7/2556 Endocrine system - Wikipedia, the free encyclopedia en.wikipedia.org/wiki/Endocrine_system 1/20 Endocrine system From Wikipedia, the free encyclopedia The endocrine system is the system of glands, each of which secretes different types of hormones directly into the bloodstream (some of which are transported along nerve tracts [citation needed] ) to maintain homeostasis. The endocrine system is in contrast to the exocrine system, which secretes its chemicals using ducts. The word endocrine derives from the Greek words "endo" meaning inside, within, and "crinis" for secrete. The endocrine system is an information signal system like the nervous system, yet its effects and mechanism are classifiably different. The endocrine system's effects are slow to initiate, and prolonged in their response, lasting from a few hours up to weeks. The nervous system sends information very quickly, and responses are generally short lived. Hormones are substances (chemical mediators) released from endocrine tissue into the bloodstream where they travel to target tissue and generate a response. Hormones regulate various human functions, including metabolism, growth and development, tissue function, sleep, and mood. The field of study dealing with the endocrine system and its disorders is endocrinology, a branch of internal medicine. Features of endocrine glands are, in general, their ductless nature, their vascularity, and usually the presence of intracellular vacuoles or granules storing their hormones. In contrast, exocrine glands, such as salivary glands, sweat glands, and glands within the gastrointestinal tract, tend to be much less vascular and have ducts or a hollow lumen. In addition to the specialised endocrine organs mentioned above, many other organs that are part of other body systems, such as the kidney, liver, heart and gonads, have secondary endocrine functions. For example the kidney secretes endocrine hormones such as erythropoietin and renin. The endocrine system is made of a series of glands that produce chemicals called hormones. A number of glands that signal each other in sequence are usually referred to as an axis, for example, the hypothalamic- pituitary-adrenal axis. As opposed to endocrine factors that travel considerably longer distances via the circulatory system, other signaling molecules, such as paracrine factors involved in paracrine signalling diffuse over a relatively short distance. Contents 1 Endocrine organs and known secreted hormones 1.1 Hypothalamus 1.2 Pineal body (epiphysis) 1.3 Pituitary gland (hypophysis) 1.3.1 Anterior pituitary lobe (adenohypophysis) 1.3.2 Posterior pituitary lobe (neurohypophysis) 1.4 Thyroid 1.5 Alimentary system 1.5.1 Stomach 1.5.2 Duodenum 1.5.3 Liver 1.5.4 Pancreas 1.6 Kidney 1.7 Adrenal glands
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2/7/2556 Endocrine system - Wikipedia, the free encyclopedia
en.wikipedia.org/wiki/Endocrine_system 1/20
Endocrine systemFrom Wikipedia, the free encyclopedia
The endocrine system is the system of glands, each of which secretes different types of hormones directly into
the bloodstream (some of which are transported along nerve tracts[citation needed]) to maintain homeostasis.The endocrine system is in contrast to the exocrine system, which secretes its chemicals using ducts. The wordendocrine derives from the Greek words "endo" meaning inside, within, and "crinis" for secrete. The endocrinesystem is an information signal system like the nervous system, yet its effects and mechanism are classifiablydifferent. The endocrine system's effects are slow to initiate, and prolonged in their response, lasting from a fewhours up to weeks. The nervous system sends information very quickly, and responses are generally short lived.Hormones are substances (chemical mediators) released from endocrine tissue into the bloodstream where theytravel to target tissue and generate a response. Hormones regulate various human functions, includingmetabolism, growth and development, tissue function, sleep, and mood. The field of study dealing with theendocrine system and its disorders is endocrinology, a branch of internal medicine.
Features of endocrine glands are, in general, their ductless nature, their vascularity, and usually the presence ofintracellular vacuoles or granules storing their hormones. In contrast, exocrine glands, such as salivary glands,sweat glands, and glands within the gastrointestinal tract, tend to be much less vascular and have ducts or ahollow lumen.
In addition to the specialised endocrine organs mentioned above, many other organs that are part of other bodysystems, such as the kidney, liver, heart and gonads, have secondary endocrine functions. For example thekidney secretes endocrine hormones such as erythropoietin and renin.
The endocrine system is made of a series of glands that produce chemicals called hormones. A number ofglands that signal each other in sequence are usually referred to as an axis, for example, the hypothalamic-pituitary-adrenal axis.
As opposed to endocrine factors that travel considerably longer distances via the circulatory system, othersignaling molecules, such as paracrine factors involved in paracrine signalling diffuse over a relatively shortdistance.
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Secreted hormone From cells Effect
Melatonin Pinealocytes
Antioxidant
Monitors the circadian rhythm including inducement of
drowsiness and lowering of the core body temperature
Pituitary gland (hypophysis)
The pituitary gland (or hypophysis) is an endocrine gland about the size of a pea and weighing 5 grams (0.18 oz)in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small,bony cavity (sella turcica) covered by a dural fold (diaphragma sellae). The pituitary is functionally connected tothe hypothalamus by the median eminence via a small tube called the infundibular stem or pituitary stalk. Thepituitary fossa, in which the pituitary gland sits, is situated in the sphenoid bone in the middle cranial fossa at thebase of the brain. The pituitary gland secretes nine hormones that regulate homeostasis and the secretion of
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Secreted hormone Abbreviation From cells Effect
Atrial-natriureticpeptide
ANPCardiacmyocytes
Reduce blood pressure by:
reducing systemic vascular resistance, reducingblood water, sodium and fats
Brain natriureticpeptide
BNPCardiacmyocytes
(To a lesser degree than ANP) reduce bloodpressure by:
reducing systemic vascular resistance, reducingblood water, sodium and fats
Bone marrow
Secreted hormone From cells Effect
Thrombopoietin liver and kidney cells stimulates megakaryocytes to produce platelets[3]
Adipose tissue
Secreted hormone From cells Effect
Leptin (Primarily) Adipocytes decrease of appetite and increase of metabolism.
Estrogens[11] (mainly
Estrone)Adipocytes
Diffuse Neuro-Endocrine System (DNES)
Main article: Diffuse neuro-endocrine system
The Diffuse Neuro-Endocrine System (DNES) comprises hormone-secreted cells, that have commonalities withneurons and are found in the Epithelium of organs of the body.
Major endocrine systems
The human endocrine system consists of several systems that operate via feedback loops. Several important
feedback systems are mediated via the hypothalamus and pituitary.[12]
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Disability-adjusted life year for
endocrine disorders per
100,000 inhabitants in 2002.[25]
no data
less than 80
80-160
160-240
240-320
320-400
400-480
480-560
560-640
640-720
720-800
800-1000
more than 1000
Extensive bidirectional interactions exist between the endocrine system and the immune system.[13] Cortisol has
major immunosuppressive effects,[14][15] and dopamine has immunomodulatory functions.[16] On the other hand,cytokines produced during inflammation activate the HPA axis at all three levels, sensible to negative
feedback.[17] Moreover cytokines stimulate hepcidin release from the liver, which is eventually responsible for
the anemia of chronic disease.[18]
In other species
A neuroendocrine system has been observed in all animals with a nervous system and all vertebrates have an
hypothalamus-pituitary axis.[19] All vertebrates have a thyroid, which in amphibians is also crucial for
transformation of larvae into adult form.[20][21] All vertebrates have adrenal gland tissue, with mammals unique in
having it organized into layers.[22] All vertebrates have some form of renin-angiotensin axis, and all tetrapods
have aldosterone as primary mineralocorticoid.[23][24]
Diseases
Main article: Endocrine diseases
Diseases of the endocrine system are common,[26] includingconditions such as diabetes mellitus, thyroid disease, and obesity.Endocrine disease is characterized by disregulated hormone release (aproductive pituitary adenoma), inappropriate response to signaling(hypothyroidism), lack of a gland (diabetes mellitus type 1, diminishederythropoiesis in chronic renal failure), or structural enlargement in acritical site such as the thyroid (toxic multinodular goitre).Hypofunction of endocrine glands can occur as a result of loss ofreserve, hyposecretion, agenesis, atrophy, or active destruction.Hyperfunction can occur as a result of hypersecretion, loss ofsuppression, hyperplastic or neoplastic change, or hyperstimulation.
Endocrinopathies are classified as primary, secondary, or tertiary.Primary endocrine disease inhibits the action of downstream glands.Secondary endocrine disease is indicative of a problem with thepituitary gland. Tertiary endocrine disease is associated withdysfunction of the hypothalamus and its releasing
hormones.[citation needed]
As the thyroid, and hormones have been implicated in signaling distanttissues to proliferate, for example, the estrogen receptor has beenshown to be involved in certain breast cancers. Endocrine, paracrine,and autocrine signaling have all been implicated in proliferation, one of
the required steps of oncogenesis.[27]
Other types of signaling
The typical mode of cell signaling in the endocrine system is endocrine signaling. However, there are also other
modes, i.e., paracrine, autocrine, and neuroendocrine signaling.[28] Purely neurocrine signaling between neurons,on the other hand, belongs completely to the nervous system.
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Autocrine
Main article: Autocrine signalling
Autocrine signaling is a form of signaling in which a cell secretes a hormone or chemical messenger (called theautocrine agent) that binds to autocrine receptors on the same cell, leading to changes in the cells.
Paracrine
Main article: Paracrine signalling
Paracrine signaling is a form of cell signaling in which the target cell is near the signal-releasing cell, altering thebehavior or differentiation of those competent cells.
Juxtacrine
Main article: Juxtacrine signalling
Juxtacrine signaling is a type of intercellular communication that is transmitted via oligosaccharide, lipid, orprotein components of a cell membrane, and may affect either the emitting cell or the immediately adjacent cells.
It occurs between adjacent cells that possess broad patches of closely opposed plasma membrane linked bytransmembrane channels known as connexons. The gap between the cells can usually be between only 2 and4 nm.
Unlike other types of cell signaling (such as paracrine and endocrine), juxtacrine signaling requires physicalcontact between the two cells involved.
Juxtacrine signaling has been observed for some growth factors, cytokine and chemokine cellular signals.
See also
Releasing hormonesNeuroendocrinology
Nervous systemEndocrine disruptor
Human anatomy#Major organ systemsEndocrine diseaseEndocrinology
References
1. ^ Colorado State University - Biomedical Hypertextbooks - Somatostatin(http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/otherendo/somatostatin.html)
2. ^ Endo K, Matsumoto T, Kobayashi T, Kasuya Y, Kamata K (February 2005). "Diabetes-related changes incontractile responses of stomach fundus to endothelin-1 in streptozotocin-induced diabetic rats"
4. ̂a b Physiology at MCG 5/5ch4/s5ch4_17(http://web.archive.org/web/20080401093403/http://www.lib.mcg.edu/edu/eshuphysio/program/section5/5ch4/s5ch4_17.htm)
5. ^ Pentikäinen V, Erkkilä K, Suomalainen L, Parvinen M, Dunkel L (May 2000). "Estradiol acts as a germinalcell survival factor in the human testis in vitro" (http://jcem.endojournals.org/cgi/pmidlookup?
6. ̂a b c d Placental Hormones (http://www.vivo.colostate.edu/hbooks/pathphys/reprod/placenta/endocrine.html)
7. ^ Physiology at MCG 5/5ch9/s5ch9_13(http://web.archive.org/web/20080401093403/http://www.lib.mcg.edu/edu/eshuphysio/program/section5/5ch9/s5ch9_13.htm)
8. ^ Hould F, Fried G, Fazekas A, Tremblay S, Mersereau W (1988). "Progesterone receptors regulate gallbladder
12. ^ Sherwood, L. (1997). Human Physiology: From Cells to Systems. Wadsworth Pub Co
13. ^ Turnbull, AV; Rivier, CL (1999 Jan). "Regulation of the hypothalamic-pituitary-adrenal axis by cytokines:actions and mechanisms of action." (http://physrev.physiology.org/content/79/1/1.long). Physiological reviews
14. ^ O'Connor, TM; O'Halloran, DJ; Shanahan, F (2000 Jun). "The stress response and the hypothalamic-pituitary-adrenal axis: from molecule to melancholia." (http://qjmed.oxfordjournals.org/content/93/6/323.full).
QJM : monthly journal of the Association of Physicians 93 (6): 323–33. PMID 10873181(//www.ncbi.nlm.nih.gov/pubmed/10873181).
15. ^ Tsigos, C; Chrousos, GP (2002 Oct). "Hypothalamic-pituitary-adrenal axis, neuroendocrine factors andstress." (http://cfids-cab.org/cfs-inform/Neuroendocrin/tsigos.chrousos02.pdf). Journal of psychosomatic
research 53 (4): 865–71. PMID 12377295 (//www.ncbi.nlm.nih.gov/pubmed/12377295).
16. ^ Sarkar, C; Basu, B; Chakroborty, D; Dasgupta, PS; Basu, S (2010 May). "The immunoregulatory role ofdopamine: an update." (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2856781/). Brain, behavior, and
17. ^ Silverman, Marni N.; Pearce, Brad D.; Biron, Christine A.; Miller, Andrew H. (1 March 2005). "ImmuneModulation of the Hypothalamic-Pituitary-Adrenal (HPA) Axis during Viral Infection"
18. ^ Andrews, Nancy C. (30 April 2004). "Anemia of inflammation: the cytokine-hepcidin link"
(http://www.ncbi.nlm.nih.gov/pmc/articles/PMC398435/). Journal of Clinical Investigation 113 (9): 1251–1253. doi:10.1172/JCI200421441 (http://dx.doi.org/10.1172%2FJCI200421441).
19. ^ Hartenstein, V (2006 Sep). "The neuroendocrine system of invertebrates: a developmental and evolutionaryperspective." (http://joe.endocrinology-journals.org/content/190/3/555.full.pdf). The Journal of endocrinology
20. ^ DICKHOFF, WALTON W.; DARLING, DOUGLAS S. (1 January 1983). "Evolution of Thyroid Function
and Its Control in Lower Vertebrates". Integrative and Comparative Biology 23 (3): 697–707.doi:10.1093/icb/23.3.697 (http://dx.doi.org/10.1093%2Ficb%2F23.3.697).
21. ^ GALTON, VALERIE ANNE (1 January 1988). "The Role of Thyroid Hormone in Amphibian Development".
Integrative and Comparative Biology 28 (2): 309–318. doi:10.1093/icb/28.2.309
24. ^ Colombo, L; Dalla Valle, L; Fiore, C; Armanini, D; Belvedere, P (2006 Apr). "Aldosterone and the conquest
of land.". Journal of endocrinological investigation 29 (4): 373–9. PMID 16699307(//www.ncbi.nlm.nih.gov/pubmed/16699307).
25. ^ "Mortality and Burden of Disease Estimates for WHO Member States in 2002"(http://www.who.int/entity/healthinfo/statistics/bodgbddeathdalyestimates.xls) (xls). World HealthOrganization. 2002.
26. ^ Kasper (2005). Harrison's Principles of Internal Medicine. McGraw Hill. p. 2074. ISBN 0-07-139140-1.
27. ^ Bhowmick NA, Chytil A, Plieth D et al. (February 2004). "TGF-beta signaling in fibroblasts modulates the
28. ^ [1] (http://www.med-ed.virginia.edu/public/CourseSitesDocs/CellandTissueStructure/handouts/unrestricted/original/MMHndt_Endocrine.htm)University of Virginia - HISTOLOGY OF THE ENDOCRINE GLANDS(http://www.youtube.com/watch?v=AmRZnRp8_B8l)
External links
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