Types of Circulation
Category : 11th Class
Circulatory system in various groups of animals can be classified as follows :
(1) Intracellular circulation : Occurs inside the individual cells where the distribution of substances is through cyclosis of cell cytoplasm. Example – Protozoans.
(2) Extracellular circulation : When the distribution of the substances occurs inside the body through extracellular or intracellular fluids. This is of following types –
(i) Extra organismic circulation : Canal system in porifera, water vascular system in Echinoderms and gastrovascular system in coelenterates.
(ii) Intra-organismic circulation : It involves circulation of body fluids. It is of following types –
(a) Parenchymal circulation : In platyhelminthes, the fluid filled spaces present in the mesodermal parenchyma tissue between body wall and internal organs are used in the distribution of substances.
(b) Coelomic circulation : Coelomic fluid is concerned with the transport of substances. Example – pseudocoelomic fluid in the roundworms and haemolymph in Arthropods.
(c) Blood vascular system : It contains blood and a pumping structure (heart) for circulation of materials inside the body. It is open circulatory system and closed circulatory system.
Differences between open and closed circulatory system
|
S.N. |
Open circulatory system |
Closed circulatory system |
|
1. |
In open circulatory system blood flows through large open spaces and channels called lacunae and sinuses among the tissues. |
In closed circulatory system blood flows through a closed system of chambers called heart and blood vessels. |
|
2. |
Tissues are in direct contact with the blood. |
Blood does not come in direct contact with tissue. |
|
3. |
Blood flow is very slow and blood has very low pressure. |
Blood flow is quite rapid and blood has a high pressure. |
|
4. |
Exchange of gases and nutrients takes place directly between blood and tissues. |
Nutrients and gases pass through the capillary wall to the tissue fluid from where they are passed on to the tissues. |
|
5. |
Less efficient as volume of blood flowing through a tissue cannot be controlled as blood flows out in open space. |
More efficient as volume of blood can be regulated by the contraction and relaxation of the smooth muscles of the blood vessels. |
|
6. |
Open circulatory system is found in higher invertebrates like most arthropods such as prawn, insects, etc., and in some molluscs (snails, clams, oyster) |
Closed circulatory system is found in echinoderms, some molluscs, (squids) annelids and all vertebrates. |
|
7. |
Respiratory pigment, if present, is dissolved in plasma; RBCs are not present. |
Respiratory pigment is present and may be dissolved in plasma but is usually held in RBCs. |
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