hypophyseal portal system

Examples of hypophyseal portal system in the following topics:

• Hypothalamic-Pituitary Axis

  • The collection of these glands makes up the endocrine system.
  • The hypothalamus in vertebrates integrates the endocrine and nervous systems.
  • This capillary network is a part of the hypophyseal portal system which carries substances from the hypothalamus to the anterior pituitary and hormones from the anterior pituitary into the circulatory system.
  • A portal system carries blood from one capillary network to another; therefore, the hypophyseal portal system allows hormones produced by the hypothalamus to be carried directly to the anterior pituitary without first entering the circulatory system.
  • The regulatory hormones travel from the hypothalamus through the hypophyseal portal system to the anterior pituitary where they exert their effect.

• 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.

• Post-and-Lintel Construction

  • Post-and-lintel architecture is a fundamental structural system in which a horizontal header is supported by two vertical columns.
  • It is often found over portals, doors, windows, and fireplaces.
  • The post-and-lintel method is a fundamental construction system that can be found in Neolithic, Ancient Greek, and Ancient Egyptian architecture.
  • The biggest disadvantage of the post-and-lintel system is the limited amount of weight that it can support.
  • There are two main force vectors at work in the post-and-lintel system.