Let me share with you a difference between single circuit heart and double circuit heart.
| Aspect | Single-Circuit Heart | Double-Circuit Heart |
| Introduction | Blood flows through the heart and then to the body tissues before returning to the heart | Blood flows through the heart and then to the lungs (pulmonary circuit) and body tissues (systemic circuit) before returning to the heart |
| Number of Circuits | One circuit | Two circuits |
| Oxygenation of blood | Blood is oxygenated in the gills or lungs and then circulated to the rest of the body | Blood is oxygenated in the lungs (pulmonary circuit) and then circulated to the rest of the body (systemic circuit) |
| Efficiency | Less efficient in supplying oxygen to the body tissues | More efficient in supplying oxygen to the body tissues due to separate pulmonary and systemic circuits |
| Valves in the Heart | Generally has a single atrioventricular valve | Has two atrioventricular valves (one for each ventricle) and two semilunar valves (one for each ventricle) |
| Regulation of blood pressure | Blood pressure is less regulated | Blood pressure is more efficiently regulated due to the separate pulmonary and systemic circuits |
| Examples | · Fish · Some amphibians |
· Mammals
· Birds · Some reptiles |