Clams and Oysters

Circulatory System



Most mollusks including clams and oysters have an open circulatory system. Cephalopods such as squid and octopus have closed circulatory systems. The ventricle, pericardium, intestine, and auricle are all vital parts of the open circulatory system of all clams/oysters.


Blood is pumped out of the heart and goes through a few large vessels to the tissues where it exits the arteries and enters large spaces where it passes over the cells of the various organs. It then collects into large internal spaces called lacunae from which it passes through the kidney and gills, ultimately returning to the heart to complete the circuit.