hypophyseal portal system

Examples of hypophyseal portal system in the following topics:

• Hypothalamus

  • The hypothalamus serves as a gateway between the nervous system and endocrine system.
  • One of the most important functions of the hypothalamus is linking the nervous system to the endocrine system via the pituitary gland (hypophysis).
  • These hormones are released into the bloodstream and target other organ systems, most notably the pituitary.
  • The hypothalamus affects the endocrine system and governs emotional behavior such as anger and sexual activity.
  • Most of the hypothalamic hormones generated are distributed to the pituitary via the hypophyseal portal system.

• Blood Supply to the Liver

  • In the hepatic portal system, the liver receives a dual blood supply from the hepatic portal vein and hepatic arteries.
  • In the hepatic portal system, the liver receives a dual blood supply from the hepatic portal vein and hepatic arteries.
  • A portal system is a venous structure that enables blood from one set of capillary beds to drain into another set of capillary beds, without first returning this blood to the heart.
  • The majority of capillaries in the body drain directly into the heart, making portal systems unusual.
  • The hepatic portal system connects the capillaries of the gastrointestinal tract with the capillaries in the liver .

• Hepatic Portal Circulation

  • The hepatic portal system is responsible for directing blood from parts of the gastrointestinal tract to the liver.
  • The hepatic portal system is the system of veins comprising the hepatic portal vein and its tributaries.
  • It functions to supply the liver with metabolites and ensures that ingested substances are processed in the liver before reaching the systemic circulation, limiting the damage ingested toxins may cause.
  • The hepatic portal vein supplies about 75% of the blood the liver requires, with the other 25% supplied by the hepatic artery.
  • Blood from the hepatic artery is oxygenated but nutrient-poor compared to that supplied by the hepatic portal vein.

• The Posterior Pituitary

  • The posterior pituitary (or neurohypophysis) comprises the posterior lobe of the pituitary gland and is part of the endocrine system.
  • These axons release peptide hormones into the capillaries of the hypophyseal circulation.
  • These are then stored in neurosecretory vesicles (Herring bodies) before being secreted by the posterior pituitary into the systemic bloodstream.
  • The infundibular stalk, also known as the infundibulum or pituitary stalk, bridges the hypothalamic and hypophyseal systems.

• Transport of Hormones

  • The endocrine system is a system of ductless glands that secrete hormones directly into the circulatory system to be carried long distances to other target organs that regulate key body and organ functions.
  • Some endocrine glands secrete into a portal system rather than the systemic circulation that allows for the direct targeting of hormones.
  • For example, hormones secreted by the pancreas pass into the hepatic portal vein that transports them directly to the liver.
  • Once within the circulatory system a small proportion of hormones circulate freely, however the majority are bound with a transport protein.
  • Describe the way in which hormones are transported in the endocrine system

• Veins

  • Although most veins take blood back to the heart, portal veins carry blood between capillary beds.
  • Since this is an important function in mammals, damage to the hepatic portal vein can be dangerous.
  • Blood clotting in the hepatic portal vein can cause portal hypertension, which results in a decrease of blood fluid to the liver.
  • Veins are classified in a number of ways, including superficial vs. deep, pulmonary vs. systemic, and large vs. small:
  • Systemic veins - Systemic veins drain the tissues of the body and deliver deoxygenated blood to the heart.

• Principal Veins

  • In the circulatory system, veins are blood vessels that carry blood towards the heart.
  • Deep veins are often of larger caliber than superficial veins and carry the majority of the blood within the circulatory system.
  • The above veins form part of the systemic circulatory system.
  • The hepatic portal vein carries blood from the gastrointestinal tract to the liver.
  • The portal vein is often described as a false vein because it conducts blood between capillary networks rather than between a capillary network and the heart.

• The Anterior Pituitary

  • A major organ of the endocrine system, the anterior pituitary (also called the adenohypophysis) is the glandular, anterior lobe of the pituitary gland.
  • Follicle-stimulating hormone is a glycoprotein hormone that targets the gonads and effects the growth of the reproductive system.
  • At this site, these neurons can release substances into the small blood vessels that travel directly to the anterior pituitary gland (the hypothalamo-hypophysial portal vessels).
  • The anterior pituitary, in yellow, is linked to the hypothalamus by a portal system.

• Venous Blood Pressure

  • Blood pressure generally refers to the arterial pressure in the systemic circulation.
  • However, measurement of pressures in the human venous system and the pulmonary vessels play an important role in intensive care medicine and are physiologically important in ensuring proper return of blood to the heart, maintaining flow in the closed circulatory system.
  • Jugular venous pressure (JVP), the indirectly observed pressure over the venous system.
  • Portal venous pressure or the blood pressure in the portal vein.
  • TPR is primarily a function of the resistance of the systemic circulation.

• Liver Function

  • The human liver is thought to be responsible for up to 500 separate functions, usually in combination with other systems and organs.
  • The liver is responsible for immunological effects, acting as a 'sieve' for antigens carried to it via the portal system.