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
Phylum Rhodophyta (Red algae) 1) The photosynthetic pigments include red pigments (phycoerythrin) and blue pigment (phycocyanin) apart from chlorophyll, of which red pigment pr

Q. What is the chemical equation of photosynthesis? The chemical equation of photosynthesis is given below: 6 CO 2 + 6 H 2 O + light --> C 6 H 12 O 6 + 6 O 2

What is protein? 1) Protein is a source of backup energy that your body keeps, a large difficult molecule made up of one or more chains of amino acids. Proteins perform a wide

Determine Push-ups Test for check the Body Strength? Push-ups is another test done to measure muscular strength, as well as, endurance and done on a parallel bar. The subject

Accidents in Industry Workplace It is a hard fact to bear in mind that accidents in industry workplace are to be avoided or discarded and efforts in this direction has been in

Calcium antagonists are not recommended for the treatment of CHF because of their negative inotropic effects. However, second-generation dihydropyridine-type calcium antagonists su

Long ago, there lived an Australopithecus girl by the name of Lucy. She died 3.2 million years ago. There are a few molecules of Lucy’s carbon in YOU! Starting from the gaseous C

Diastolic dysfunction is  responsible for one third of cases of heart  failure alone and rest two  third of cases in  combination with systolic dysfunction. Diastolic dysfunction c

Explain about the Brownian ratchets and molecular motors ? How work is carried out by molecules within biological cells is essential to understanding how cells function. A clue

What are the three categories in which food protein sources can be divided into Protein food sources can be separated into the following three categories: Proteins of pl