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
in what part of the human body aschelminthes found?

Vital Dye Staining In this type of method, a piece of agar or cellophane soaked in the solution of a vital dye (Neutral Red, Nile Blue Sulphate, and Bismarck Brown etc.) is a

recent research on golgi bodies


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

In which period of meiosis does the pairing of homologous chromosomes occur? The pairing of homologous chromosomes is an essential step for meiosis because the rightness of the

Structure and development of leaf

EXTERNAL GENITALIA - Vestibule is covered by 2 pairs of lips labia majoris and labia minoris. At the anterior junction of labia minoris a small erectile clitoris presen

What do enzymes do to a reaction? Indicate all that are correct. a. Lower the activation energy b. Reverse the equilibrium c. Lower the equilibrium d. Increase the reac

what is the classification of skeletal tissue?