General Blood Flow Sequence:
1. Deoxygenated Blood: Enters the heart through the right atrium.
2. Right Ventricle: Pumps deoxygenated blood to the lungs via the pulmonary artery.
3. Lungs: Blood picks up oxygen and releases carbon dioxide.
4. Left Atrium: Oxygenated blood returns to the heart through the pulmonary veins.
5. Left Ventricle: Pumps oxygenated blood out to the body via the aorta.
6. Body Tissues: Oxygen is delivered to cells, and carbon dioxide is picked up.
7. Deoxygenated Blood: Returns to the heart via the vena cava.
Key Differences:
* Reptiles: Have a three-chambered heart (two atria and one ventricle). This means there is some mixing of oxygenated and deoxygenated blood in the ventricle. The ventricle has a partial septum, but it isn't completely divided.
* Mammals: Have a four-chambered heart (two atria and two ventricles). This ensures complete separation of oxygenated and deoxygenated blood, allowing for a higher metabolic rate and more efficient delivery of oxygen to tissues.
Simplified Illustration:
Reptile:
* Deoxygenated blood (right atrium) -> Ventricle (some mixing) -> Lungs -> Oxygenated blood (left atrium) -> Ventricle (some mixing) -> Body
Mammal:
* Deoxygenated blood (right atrium) -> Right ventricle -> Lungs -> Oxygenated blood (left atrium) -> Left ventricle -> Body
Important Note: The three-chambered heart of reptiles is less efficient than the four-chambered heart of mammals, leading to a lower metabolic rate and generally cooler body temperatures (except for some exceptions like crocodiles).