hipófisis or pituitary gland, (Aristotle attributed the function to him of secretar flema, in pituita Latin, of there the pituitary name), is one complex Gland that lodges in a bony space called Turkish Chair of the bone Esfenoides, located in the base of Skull, in the cerebral grave average, that connects with Hipotálamo through pituitary stem or hipofisario stem. G has an approximated weight of 0. The hipófisis is Gland that controls the rest, among them Thyroid .

It consists of three parts:

  • previous Lobe or Adenohipófisis that embryologically comes from a pharyngal outline ( Stock market of Rathke ) and is responsible for the numerous secretion of Hormones (to see more ahead).

  • Average Hipófisis : produces two Polypeptides called Melanotropinas or stimulating hormones of Melanocitos (HEM), that induce the increase of the synthesis of Melanin of Cells of Skin .

This can affect in ocular Melanocitosis
  • later Lobe or Neurohipófisis : coming from the evaginación of the floor of the third ventricle of Diencéfalo, which it is known him with the name infundíbulo, is united through hipofisario stem; it stores to hormones ADH and Oxitocina secretadas by amielínicas fibers of the supraoptical nuclei and paraventriculares of the neurons of the hypothalamus.

It is important to know that a tumor in the surpluses of stock-market of Rathke can cause Craneofaringioma, which compresses to the gland hipófisis.

Adenohipófisis

Adenohipófisis secretes many hormones of which six are excellent for the suitable physiological function of the organism, which they are secreted by 5 types of different cells. These cells are of Epithelial origin and like many endocrine glands, are organized in lagoons surrounded by fenestrados sinusoides capillaries to which its hormonal secretion is spilled. The types of cells were classified before agreement to their tinción, and were acidófilas, basófilas and cromófobas (or that is not dyed). But at present Immunohistochemistry is counted on techniques of, and they have been possible to identify 5 cellular types:
  • Cells somatótropas that secretan GH (acidófila).

  • Cells lactotropas that secretan PRL (acidófila).
  • Cells corticotropas that secretan ACTH (basófila).
  • Gonadotrópicas cells that secretan gonadotropinas LH, and FSH (basófila).
  • Cells tirotropas that secretan the TSH (basófila).

The cells cromófobas are in fact worn away cells and can have been anyone of the five previous ones.ta

Hormones of the adenohipófisis

  • Hormone of the growth (GH) . Protein Synthesis stimulates, and avoids the pick up of Glucose on the part of Muscle and Adipocitos in addition induces Gluconeogénesis reason why increases Glucaemia; its more important effect is perhaps than Growth of all the promotes woven and Bones altogether with Somatomedinas Reason why a deficit of this hormone causes Dwarfism and an increase (caused by Tumor acidófilo) causes Gigantism in children, and Acromegaly in adults, (consequence of the previous closing of epifisiarios discs ).
  • Prolactina (PRL) or luteotrópica hormone . stimulates the development of acinos mammary and stimulates translation of Genes for Proteins of Milk .

Other hormones are trophic hormones that have their effect in some peripheral endocrine glands:

  • stimulating Hormone of the thyroid (TSH) or tirotropina . Thyroid stimulates the production of hormones on the part of

  • stimulating Hormone of the adrenal crust (ACTH) or corticotropina . stimulates the production of hormones on the part of adrenal glands
  • luteinizante Hormone (LH) . They stimulate the production of hormones on the part of Gónadas and Ovulation .
  • stimulating Hormone of the follicle (FSH) . Same function that the previous one.

the LH and the FSH denominate Gonadotropinas since they regulate the function of the gónadas ones.

Neurohipófisis

The cells of the neurohipófisis know like Pituicitos and are not more than cells gliales of support. Therefore, the neurohipófisis is not in fact one secretory gland since it is limited to store to the secretion products of Hipotálamo . Indeed, Axoplasmas of Neurons of the nuclei supraoptical and to paraventricular of Hipotálamo secretan ADH and Oxitocina, that is stored in vesicles of the axons that of him arrive at the neurohipófisis; these hormones are secretadas by the stimulus of electrical impulses on the part of the hypothalamus.
  • antidiurética or (ADH) vasopresina Hormone . Secret in stimulus to a diminution of the plasmatic volume and as a result of the diminution in arterial Pressure that this causes, and its secretion increases to the resorption of water from túbulos renal collectors by means of the translocación to the membrane of acuaporina II; also Blood vessel constriction causes strong reason why also it is called vasopresina.

  • Oxitocina . of stimulates the contraction of mioepiteliales cells mammary glands what on the part of the breast causes to the ejection of Milk, and is stimulated by the suction. Also of the final stage of causes typical to the uterine contractions Childbirth .

Syndrome of Cushing

At the beginning of century XX, neurosurgeon Harvey Cushing (EE., 1869-1939) it began to study the pituitary gland, observing the effects of a bad operation. It discovered that if were little or too active could alter Metabolism and Growth, and gave the name him of Syndrome of Cushing. This disease, is brought about by an excess of Adrenocorticotropina (ACTH), brings about weakness in the members and fragility of Bones . Cushing described the pituitary one like " director of Orchestra endocrinica", but today one knows that the true director is Hipotálamo . The Cushing is a syndrome that affects to several systems and organs, is characterized by a cortisol hypersecretion (generally due to one hiperplasia of Hipófisis ). The symptoms of the Cushing are:

- Expensive round, rubicunda and congestive, which denominates " moon face llena".

- I accumulate of fats in the neck and nape of the neck, what is called buffalo neck.

- Central Obesity (excellent abdomen but thin extremities).

- Violáceas Striae in abdomen, thighs and breasts.

- Dolores of back.

- Increase of hair in women.

They can appear other secondary symptoms: Hypertension, Diabetes, Psychosis

Hipotalámica regulation

The hipófisis and Hipotálamo are connected by a hair system denominated System vestibule, which comes from Artery internal carotid and from Polygon of Willis and irrigates first the hypothalamus forming plexo hair primary, that drains in the glasses carries hipofisiarios that as well form plexo hair hipofisiario.

The importance of this system is that it transports liberating or hipofisiotrópicas hormones that secret the hypothalamus with regulating aims of the adenohipofisiaria secretion. These hormones are:

  • Somatoliberina (GHRH) . on the part of the hipófisis stimulates the secretion of GH.

  • Corticoliberina (ARH) . on the part of the hipófisis stimulates the secretion of ACTH.
  • Tiroliberina (TRH) . on the part of the hipófisis stimulates the secretion of TSH.
  • Gonadoliberina (LHRH) . It stimulates the secretion of LH and FSH on the part of the hipófisis.
  • inhibiting Hormone of GH (GHIH) or somatostatina . on the part of the hipófisis inhibits the secretion of GH.

Prolactina is regulated negatively by Dopamine, Neurotransmitter .

It is necessary to consider that the regulation of the secretion of hipofisiarias hormones is realized by means of a mechanism of negative feedback which settles down between the specific hypothalamus, hipofisis and receivers for each hormone, located in the organs morning call.

The process is realized in the moment in which the central nervous system receives a stimulus, the hypothalamus receives part of that stimulus and acts on the hipófisis, as well, the secret hypothalamus respective hormones in the adenohipófisis or releases those of the neurohipófisis; these are gotten up to the circulation, travel by means of the blood and are caught by specific receivers located in the organs morning call, an example is the pick up of the TSH on the part of the tiroideos lobes of the thyroid gland.

Then the organ morning call, that in any case is anyone of the endocrine glands begin to secretar its own hormones, and so a stimulus is sent to the nervous system, specifically to the hypothalamus, or directly to the hipófisis consequently the initial stimulus is resisted.

Pathology

Some upheavals associated to the hipófisis include:

.

Random links:Genetic test | Jose Garci'a You go | Ruud Hesp | Selection of soccer of Alderney | Sofia Vergara

© 2007-2008 speedlook.com; article text available under the terms of GFDL, from fr.wikipedia.org