Comparing Single & Double Circulation
Differences between single circulation in bony fish and double circulation in mammals
- Both fish and mammals have a closed circulatory system
- This means blood is contained within a system of blood vessels
- Bony fish have single circulation
- Blood moves through the heart once during each complete circuit
- The heart has two chambers
- It enters the heart from the body before being pumped to the gills
- Here blood is oxygenated before moving to the rest of the body
Single circulation diagram
Bony fish have single circulation
- Mammals have double circulation
- This means blood flows through the heart twice for each complete circuit of the body
- The heart has four chambers; two on the right and two on the left
- The right side of the heart pumps deoxygenated blood to the lungs for gas exchange; this is pulmonary circulation
- Blood then returns to the left side of the heart, so that oxygenated blood can be pumped at high pressure around the body; this is systemic circulation
Double circulation diagram
Mammals have double circulation
- The main advantages of the mammalian double circulation system include:
- Keeping oxygenated and deoxygenated blood separate, so that cells can receive blood with high oxygen levels for aerobic respiration
- Maintaining a high pressure for the transport of oxygenated blood to every part of the body
- Pumping blood at a lower pressure in the lungs so that delicate blood vessels are not damaged