Hepatic portal system

Large veins that are considered part of the portal venous system are the:

The superior mesenteric vein and the splenic vein come together to form the actual hepatic portal vein. The inferior mesenteric vein connects in the majority of people on the splenic vein, but in some people, it is known to connect on the portal vein or the superior mesenteric vein.

Roughly, the portal venous system corresponds to areas supplied by the celiac trunk, the superior mesenteric artery, and the inferior mesenteric artery.

Microscopic section through a small portal vein branch inside the liver (×250 magnified)

The benefit of first-pass metabolism, whereby substances absorbed from food in the gut pass through the liver before entering the systemic circulation, is to use the liver as a shield (a first line of defense) between (a) the food, its toxins (whatever they may be), and its metabolic intermediates/metabolites (such as ammonia) and (b) the rest of the body’s tissues, including the brain. The necessity of such a system is demonstrated by what happens when the system breaks down, as seen when advanced hepatic fibrosis in cirrhosis leads to hepatic encephalopathy in the brain owing to the blood being loaded with ammonia and other substances not conducive to brain function.

Blood flow to the liver is unique in that it receives both oxygenated and (partially) deoxygenated blood. As a result, the partial gas pressure of oxygen (pO2) and perfusion pressure of portal blood are lower than in other organs of the body. Blood passes from branches of the portal vein through cavities between «plates» of hepatocytes called sinusoids. Blood also flows from branches of the hepatic artery and mixes in the sinusoids to supply the hepatocytes with oxygen. This mixture percolates through the sinusoids and collects in a central vein which drains into the hepatic vein. The hepatic vein subsequently drains into the inferior vena cava.

The hepatic artery provides 30 to 40% of the oxygen to the liver, while only accounting for 25% of the total liver blood flow. The rest comes from the partially deoxygenated blood from the portal vein. The liver consumes about 20% of the total body oxygen when at rest. That is why the total liver blood flow is quite high, at about 1 litre a minute and up to two litres a minute. That is on average one fourth of the average cardiac output at rest.

Portal hypertension is a condition in which the blood pressure of the portal venous system is too high. It is often the result of cirrhosis of the liver.

Many drugs that are absorbed through the GI tract are substantially metabolized by the liver before reaching general circulation. This is known as the first pass effect. As a consequence, certain drugs can only be taken via certain routes. For example, nitroglycerin cannot be swallowed because the liver would deactivate the medication, but it can be taken under the tongue or transdermally (through the skin) and thus is absorbed in a way that bypasses the portal venous system. Inversely, dextromethorphan, a cough suppressor, is best taken orally because it needs to be metabolised by the liver into dextrorphan in order to be effective. This latter principle is that of most prodrugs.

The use of suppositories is a way to partially bypass the portal vein: the upper 1/3 of the rectum is drained into the portal vein while the lower 2/3 are drained into the internal iliac vein that goes directly in the inferior vena cava (thus bypassing the liver).

• Saladin, Kenneth S. (2011). Human anatomy (3rd ed.). New York: McGraw-Hill. p. 571. ISBN 9780071222075.
• Item F, Konrad D (2012). «Visceral fat and metabolic inflammation: the portal theory revisited» . Obesity Reviews. 13 (Suppl 2): 30–39. doi:10.1111/j.1467-789X.2012.01035.x. PMID 23107257. S2CID 25169877.
• Dhawan D, Sharma S (2020). «Abdominal Obesity, Adipokines and Non-communicable Diseases». The Journal of Steroid Biochemistry and Molecular Biology. 203: 105737. doi:10.1016/j.jsbmb.2020.105737. PMC . PMID 32818561.

На основании Вашего запроса эти примеры могут содержать грубую лексику.

На основании Вашего запроса эти примеры могут содержать разговорную лексику.

The enterprise information portal system is a continuing initiative from the 2009/10 budget period that will consolidate the wide range of systems and present them in a unified and logical way.

Создание общеорганизационного информационного портала является инициативой, осуществление которой продолжается с 2009/10 финансового года; реализация этой инициативы позволит объединить широкий круг систем и представить их в едином и логичном формате.

A portal venous system is a series of veins or venules that directly connect two capillary beds.

Enterprise portal is a system in which we keep a record of tasks, store electronic documents, and a knowledge warehouse.

Корпоративный портал — система, в которой мы ведем учет задач, хранение электронных документов, а так же базу знаний.

The Bitrix24 corporate portal is a system for managing intracorporate information with a wide range of integration capabilities designed for teamwork, centralized and secure storage and retrieval of documents, modern internal communications, and automation of business processes.

Корпоративный портал «Битрикс24» это система управления внутрикорпоративной информацией с большим спектром интеграционных возможностей, предназначенная для коллективной работы, централизованного и безопасного хранения и поиска документов, современных внутренних коммуникаций, автоматизации бизнес-процессов.

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The corresponding veins drain into the portal system.

These impulses have a certain amplitude and cause a periodic flow of GnRH through the portal system of blood flow to the cells of the adenohypophysis.

Эти импульсы имеют определенную амплитуду и вызывают периодическое поступление ГнРГ через портальную систему кровотока к клеткам аденогипофиза.

For portal hypertension, propranolol is a commonly used agent to lower blood pressure over the portal system.

Для портальной гипертензии пропранолол является широко используемым веществом для снижения кровяного давления в рамках портальной системы.

TIPS — transjugular intrahepatic portosystemic shunting — allows to decompress the portal system and eliminate ascitic syndrome.

ТИПС — трансъюгулярное интрапеченочное портосистемное шунтирование — позволяет провести декомпрессию портальной системы и устранить асцитический синдром.

The hypothalamic-pituitary region has a special vascular network, which is called the portal system.

Гипоталамо-гипофизарная область имеет особую сосудистую сеть, которая называется портальной системой.

A short but complex network of blood vessels, called a portal system, extends from the hypothalamus to the pituitary gland.

Короткая, но сложная сеть кровеносных сосудов, называемая портальной системой, простирается от гипоталамуса до гипофиза.

Xoops is the abbreviation for extensible Object Oriented Portal System.

It re-imagines it as a collaborative, 3D space, with physics and interactive elements all linked by a physical portal system.

Он заново представляет его как совместное трехмерное пространство с физикой и интерактивными элементами, связанными физической портальной системой.

As opposed to other organs in the body, the majority of this blood supply (75%) comes from the venous system through the portal system.

В отличие от других органов, значительная доля кровоснабжения печени (75%) поступает из венозной системы через портальную систему.

This article is about the portal venous systems in general. For the system involving the liver, see Hepatic portal system.

In the circulatory system of vertebrates, a portal venous system occurs when a capillary bed pools into another capillary bed through veins, without first going through the heart. Both capillary beds and the blood vessels that connect them are considered part of the portal venous system.

The functional significance of such a system is that it transports products of one region directly to another region in relatively high concentrations. If the heart were involved in the blood circulation between those two regions, those products would be spread around the rest of the body.

The hypophyseal portal system portal venous system transports hormones from the hypothalamus to the pituitary gland.

In the renal portal system adrenal medulla capillaries are downstream from adrenal cortex capillaries. This portal system delivers high concentrations of adrenal cortical hormones to the adrenal medulla. In particular, glucocorticoids induce the enzymatic conversion of norepinephrine to epinephrine in the adrenal medulla. By contrast, the ganglia of the sympathetic trunk produce mainly norepinephrine because their cells aren’t bathed in high concentrations of glucocorticoids. Renal tubular capillaries are downstream from renal glomerular capillaries.

• Saladin, Kenneth S. (2011). Human anatomy (3rd ed.). New York: McGraw-Hill. p. 571. ISBN 9780071222075.
• Gallego, Carmen; Velasco, Maria; Marcuello, Pilar; Tejedor, Daniel; De Campo, Lourdes; Friera, Alfonsa (1 January 2002). «Congenital and Acquired Anomalies of the Portal Venous System». RadioGraphics. 22 (1): 141–159. doi:10.1148/radiographics.22.1.g02ja08141. ISSN 0271-5333. PMID 11796904.
• SJ, Pandol; Rafael, San. Anatomy.

Firstly, participants learned about the Mountain Geographic Information System Portal (), which had been developed to provide GIS resources that addressed sustainable development issues in the Hindu Kush-Himalayan region.

В начале заседания участники познакомились с порталом географической информационной системы для горных районов (), созданным для доступа к ресурсам ГИС по вопросам устойчивого развития региона Гиндукуш — Гималаи.

The Plan covers all major fields concerning ICT, such as the International Public Sector Accounting Standards (IPSAS), ERP, United Nations Data Centres and the United Nations System Portal.

Планом охватываются все основные области, касающиеся ИКТ, такие как международные стандарты учета в государственном секторе (МСУГС), ПОР, центры обработки данных Организации Объединенных Наций и портал системы Организации Объединенных Наций.

Transfer and presentation of the tank level in the telematics system portal

The project on the United Nations system portal is also under way.

Проект создания системного портала Организации Объединенных Наций также находится на этапе осуществления.

Другие результаты

В случае возникновения какой-либо проблемы на серверах и системах безопасности Портала вследствие небрежных действий пользователя последний несет за это соответствующую гражданскую и уголовную ответственность.

All printed magazines are equipped with RFID tags, which allows to optimize the process of issuing publications, while the anti-theft functions of the installed RFID system — portal readers manufactured by RST-Invent — ensure the safety of stock materials.

Все печатные журналы оснащены RFID — метками, что позволяет посредством ридеров оптимизировать процесс выдачи изданий, при этом антикражные функции установленной RFID-системы — портальные считыватели производства РСТ-Инвент — обеспечивают сохранность фондовых материалов.

Corey Goode explains that there are natural portal systems and current era portal systems, plus ancient portal systems, built on earth and left behind by ancient civilisations.

A new version of the system — Automated system «Portal for the development of economic activities» was developed and functioned as.

Разработана новая версия системы — «Автоматизированная система «Портал по развитию экономической деятельности», которая функционировала как «Сайт».

The hypophyseal portal system is a system of blood vessels in the microcirculation at the base of the brain, connecting the hypothalamus with the anterior pituitary. Its main function is to quickly transport and exchange hormones between the hypothalamus arcuate nucleus and anterior pituitary gland. The capillaries in the portal system are fenestrated (have many small channels with high vascular permeability) which allows a rapid exchange between the hypothalamus and the pituitary. The main hormones transported by the system include gonadotropin-releasing hormone, corticotropin-releasing hormone, growth hormone–releasing hormone, and thyrotropin-releasing hormone.

• Gonadotropin-releasing hormone (GnRH): regulates the release of follicle stimulating hormone and luteinizing hormone from the anterior pituitary; this pathway plays a critical role in reproductive activity and development
• Corticotropin-releasing hormone (CRH): regulates the release of adrenocorticotropic hormone from the anterior pituitary; this cascade is primarily responsible for stress responses
• Growth hormone-releasing hormone (GHRH): regulates the release of growth hormone from the anterior pituitary; as the name suggests, its main function is to help control cell growth, metabolism, and reproduction
• Thyrotropin-releasing hormone (TRH): regulates the release of thyroid-stimulating hormone from the anterior pituitary; functions to mediate various responses in the thyroid gland, including additional hormone synthesis

Over- or under-function as well as insufficiencies of the hypothalamus or the pituitary gland can cause a negative effect on the ability of the hypophyseal portal system to exchange hormones between both structures rapidly. This can have major effects on the respective target glands, making it impossible for them to carry out their functions properly. Occlusions and other issues in the blood vessels of the hypophysial portal system can also cause complications in the exchange of hormones between the hypothalamus and the pituitary gland.

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