Circulation In  Animal

Circulation is served by a fluid as blood/ lymph that circulates through the body in a regular manner, receiving & distributing materials in the way.

The main materials that need transport in the body include nutrients, gases, hormones & nitrogenous wastes.

Many types of fluid circulation have been evolved by animals.

(A)     INTRA CELLULAR CIRCULATION - In amoeba, peramecium circulation is done by cyclosis.

(B)     EXTRA CELLULAR CIRCULATION - In multicellular animals fluid circulates outsdies the cell. It is of many kinds -

1.      Extra Organismic Circulation -

Sponges, hydra do not have circulatory fluid, and circulate the surrounding water through the cavities in their bodies with the help of flagella.

(i) Sponges - It consits of water canal system. It includes ostia, incurrent canal, spongocoel & osculum. Radial canals are lined by choanocytes cells. This system helps sponges in feeding, respiration, excretion and reproduction.

(ii) Hydra - It consists of coelenteron or gestrovascular cavity lined by dermis open outside by single aperture i.e. mouth (Ingestion & egestion).

2.      Intra Organismic Circulation -

Higher animals need quicker supply of O₂ & food to their tissue & quicker removal of waste materials.

(i) Parenchymal circulation - In platyhelmenthes, coelome is acoelomate filled with mesodermal parenchymal cells, helpful in circulation.

(ii) Body cavity circulation - In aschahelminthes pseudocoelome present filled with pseudocoelomic fluid, helpful in circulation.

(iii) Blood vascular system or cardio vascular system - It is of two types - open & closed. In open circulatory system blood vessels are absent, so all organs are dipped in haemolymph. eg. arthropoda, mollusca. In closed circulatory system blood vessels are present. eg. annelida, vertebreta.