Portal circulation, Biology

PORTAL CIRCULATION

When a vein branches into set of capillary to distribute blood in some parts, such venous circulation is called portal system. Three types of portal systems are found in vertebrates:

(i) Hepatic Portal System

Hepatic portal vein carries blood that is collected by coeliacomesentric (or lienogastric) vein from alimentary canal and redistribute it in the liver. This enables liver to screen the substances absorbed in small intestine before allowing it to pass in the body.

In frog hepatic portal vein is formed by the union of coeliacomesentric vein and anterior abdominal vein.

(ii) Renal Portal System

It is absent in mammal but well developed in some fishes, all amphibians and lower reptiles.

Veins from hindlimbs and other posterior parts of body join to form renal portal vein which branches into kidney.

Here the excretory substances are filtered from blood.

Femoral veins from outer sides of hind limbs divide into outer renal portal vein and inner pelvic vein.

Sciatic vein from inner side of hind limb joins renal portal vein of its side while pelvic veins of left and right sides unite to form anterior abdominal vein running as main vein along the ventral body wall.

Blood is drained out from kidney by renal vein.

(iii) Hypothalamo-hypophysical Portal System

The vein collecting blood from anterior part and hypothalamus of brain enter and pituitary as hypophysical portal vein and branches into capillaries.

Through this system hormones of hypothalamus reach the pituitary.

Posted Date: 10/2/2012 3:15:03 AM | Location : United States







Related Discussions:- Portal circulation, Assignment Help, Ask Question on Portal circulation, Get Answer, Expert's Help, Portal circulation Discussions

Write discussion on Portal circulation
Your posts are moderated
Related Questions
what are the names of twelve cranial nerves

1. Compute the mean energy per nuclear disintegration, A, for 99m TC if 2.0 x 10 9 Bq of this isotope is injected into a patient. Assume that one-half of the administered dose is

Molecular Hydrogen N 2 -fixing organisms also produce a membrane bound enzyme called uptake-hydrogenase under N 2 -fixing condition. The physiological significance of the pres

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

excretory organs of agama lizard

Explain about Pergingival Regenerative Therapy In case of one stage implants being treated or when the prosthesis has to be maintained a  Pergingival Regenerative Therapy is d

A 'rag doll' seed tester Fold a square metre of muslin twice in the similar direction. Near one end mark out eight or ten squares about 5 cm by 5cm with a pencil. Number the sq

Morphogenetic Movements Gastrulation is a dynamic process including a variety of coordinated movements of cells of dissimilar areas of the blastula. The movements of cells in


Illustrate about Whey protein Whey protein concentrate (WPC) is a highly nutritious ingredient manufactured from fresh dairy whey and it is spray dried to provide an excellent