Portal circulation, Biology

Assignment Help:

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.


Related Discussions:- Portal circulation

Temperature-environmental components, TEMPERATURE Temperature is a majo...

TEMPERATURE Temperature is a major physical environmental factor which profoundly influences the vital activities of living organisms like, metabolism, growth and reproduction.

Nature of disease, Q. Nature of disease? Education is very important fo...

Q. Nature of disease? Education is very important for diabetics because it is a lifelong disorder. In order to enable the patient to lead a healthy and a good quality Life free

Explain about chronic gastritis, Q. Explain about Chronic Gastritis? It...

Q. Explain about Chronic Gastritis? It precedes development of organic gastric lesion, or tissue damage. Recurrent inflammation leads to changes in enzyme activity of gastric m

Why is the aids treatment often done with a drug cocktail, Q. Why is the AI...

Q. Why is the AIDS treatment often done with a drug cocktail? The treatment of obtain immune deficiency syndrome is often done with one or more anti-retroviral drugs of differe

Explain soy protein concentrates - protein concentrates, Soy Protein Concen...

Soy Protein Concentrates The Association of American Feed Control Officials, Inc. (AAFCO) specifies soy protein concentrates as follows:  "Soy Protein Concentrate is organiz

Define the foam mat drying method, Define the Foam Mat Drying Method? T...

Define the Foam Mat Drying Method? This process is a development of the vacuum puffing but, instead of employing a vacuum to foam the material, it is initially foamed by suitab

Explain the mitotic prophase, Which of the following best explains what wou...

Which of the following best explains what would happen if recombination (crossing-over) happens during mitotic prophase? A. Recombination during mitosis will lead to segregatio

Osmosis, everything about osmosis

everything about osmosis

Why protein requirements of athletes get increased, Why Protein requirement...

Why Protein requirements of athletes get increased? Protein requirements of athletes, particularly those engaged in strength and power events, may be increased above those of s

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd