TYPES OF CIRCULATION
there are two types of circulation, single circulation and double circulation. single circulation is found in animals such as fish, in this type of circulation, blood only passes through the heart once. While in double circulation,which is found in birds and mammals, the blood goes through the heart twice, that is why it is referred to as 'double' circulation.
blood passes through the heart twice, that is why they call it 'double circulatory' system. and also, two circulatory systems take place during double circulation. deoxygenated blood from the heart is pumped to the lungs which is referred to as pulmonary circulation. while oxygenated blood from the heart to the cells of the body is referred to as systemic circulation.
ALL ARTERIES CARRY OXYGENATED BLOOD APART FROM THE PULMONARY ARTERY.
ALL VEINS CARRY DEOXYGENATED BLOOD APART FROM PULMONARY VEINS.