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The endocrine system is referring to the collection of cells, glands, and tissues of an organism that secrete hormones directly into the bloodstream (some of which are transported along nerve tracts) to control the organisms' physiological and behavioral activities. 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.
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 to the hypothalamus by the median eminence via a small tube called the infundibular stem or pituitary stalk. The pituitary fossa, in which the pituitary gland sits, is situated in the sphenoid bone in the middle cranial fossa at the base of the brain. The pituitary gland secretes nine hormones that regulate homeostasis and the secretion of other hormones.
Oxytocin and anti-diuretic hormone are not secreted in the posterior lobe, merely stored.
secretion of growth hormone from anterior pituitary gland
Lowers rate of gastric emptying Reduces smooth muscle contractions and blood flow within the intestine.[1]
Enhances effects of cholecystokinin, stops production of gastric juice
Release of bile from gallbladder, hunger suppressant
regulate cell growth and development
release of aldosterone from adrenal cortex dipsogen.
Pancreas is a mixed endocrine and exocrine gland and it secretes both enzymes and hormones.
intake of lipids and synthesis of triglycerides in adipocytes Other anabolic effects
increases blood glucose level
Inhibit release of glucagon[4] Suppress the exocrine secretory action of pancreas.
Increase absorption of calcium and phosphate from gastrointestinal tract and kidneys inhibit release of PTH
Virilizing: maturation of sex organs, formation of scrotum, deepening of voice, growth of beard and axillary hair.
Other:
Anti-inflammatory
Protein synthesis:
Coagulation:
Fluid balance:
Gastrointestinal tract:
Melanin:
Cancer:
Lung function:
Other effects on mother similar to ovarian follicle-progesterone
Inhibit immune response, towards the human embryo.
Increase insulin resistance and carbohydrate intolerance
Phosphate:
reducing systemic vascular resistance, reducing blood water, sodium and fats
The Diffuse Neuro-Endocrine System (DNES) comprises hormone-secreted cells, that have commonalities with neurons and are found in the Epithelium of organs of the body.
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]
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]
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 of the endocrine system are common,[26] including conditions such as diabetes mellitus, thyroid disease, and obesity. Endocrine disease is characterized by disregulated hormone release (a productive pituitary adenoma), inappropriate response to signaling (hypothyroidism), lack of a gland (diabetes mellitus type 1, diminished erythropoiesis in chronic renal failure), or structural enlargement in a critical site such as the thyroid (toxic multinodular goitre). Hypofunction of endocrine glands can occur as a result of loss of reserve, hyposecretion, agenesis, atrophy, or active destruction. Hyperfunction can occur as a result of hypersecretion, loss of suppression, 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 the pituitary gland. Tertiary endocrine disease is associated with dysfunction of the hypothalamus and its releasing hormones.
As the thyroid, and hormones have been implicated in signaling distant tissues to proliferate, for example, the estrogen receptor has been shown 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]
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.
Autocrine signaling is a form of signaling in which a cell secretes a hormone or chemical messenger (called the autocrine agent) that binds to autocrine receptors on the same cell, leading to changes in the cells.
Paracrine signaling is a form of cell signaling in which the target cell is near the signal-releasing cell, altering the behavior or differentiation of those competent cells.
Juxtacrine signaling is a type of intercellular communication that is transmitted via oligosaccharide, lipid, or protein 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 by transmembrane channels known as connexons. The gap between the cells can usually be between only 2 and 4 nm.
Unlike other types of cell signaling (such as paracrine and endocrine), juxtacrine signaling requires physical contact between the two cells involved.
Juxtacrine signaling has been observed for some growth factors, cytokine and chemokine cellular signals.
M: END
anat/phys/devp/horm
noco (d)/cong/tumr, sysi/epon
proc, drug (A10/H1/H2/H3/H5)
Ovary: estradiol · progesterone · activin and inhibin · relaxin (pregnancy)
Digestive system: Stomach: gastrin · ghrelin · Duodenum: CCK · Incretins (GIP, GLP-1) · secretin · motilin · VIP · Ileum: enteroglucagon · peptide YY · Liver/other: Insulin-like growth factor (IGF-1, IGF-2)
Adipose tissue: leptin · adiponectin · resistin
Skeleton: Osteocalcin
Kidney: JGA (renin) · peritubular cells (EPO) · calcitriol · prostaglandin
Apocrine, Latin, Blood, Endocrine gland, Exocrine gland
Adrenal insufficiency, Iodine deficiency, Congenital hypothyroidism, Diabetes mellitus type 1, Selenium
Hypotension, Cardiogenic shock, Septic shock, Cardiology, Distributive shock
Human body, Elsevier, Grey's Anatomy, Mark Twain, Bbc
Embryology, Gastrulation, Ectoderm, Mesoderm, Liver