Final answer:
The human heart consists of four hollow chambers: two atria and two ventricles, with each side of the heart containing one atrium and one ventricle.
Step-by-step explanation:
The human heart has four hollow chambers. The anatomy of the heart shows a division into two upper chambers called atria and two lower chambers known as ventricles. The right atrium and the left atrium serve as receiving areas for blood and push blood into the ventricles upon contraction. The ventricles are the primary pumping sections of the heart, sending blood to either the lungs or through the rest of the body. In summary, the two atria receive blood and the two ventricles pump it out.
In mammals and birds, a four-chambered heart allows for efficient separation of oxygenated and deoxygenated blood, which is crucial for their high-energy lifestyles. This adaptation is a result of convergent evolution, where two atria and two ventricles have evolved independently in these groups to meet similar life requirements.