How is the circulatory system designed in leech to compensate the heart structure?

Explanation

(i) In leech, circulation is brought about by haemocoelic system.
(ii) There are no true blood vessels.
(iii) The blood vessels are replaced by channels called haemocoelic channels or canals filled with blood-like fluid.
(iv) The coelomic fluid contains haemoglobin.
(v) There are four longitudinal channels. One I channel lies above ( dorsal) the alimentary canal, one below (ventral) the alimentary canal.
(vi) The other two channels lie on either (lateral) side of the alimentary canal which serve as heart and have inner valves.
(vii) All the four channels are connected together posteriorly in the 26th segment.