Frog hearts have a chamber where deoxygenated blood can mix with oxygenated blood. What structure in the human heart prevent such mixing?

The septum is the wall that separates the left and right sides of the human heart, keeping oxygenated blood apart from deoxygenated blood. The atria are heart chambers, the pericardium is the sac around the heart, and blood vessels carry blood to and from it. Therefore, the correct choice is the septum.

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