A dog's heart has 4 chambers. Like the heart of most mammals, the dog's heart has two atria and two ventricles. The right atrium receives deoxygenated blood from the body and pumps it to the right ventricle, which then pumps it to the lungs for oxygenation. On the other hand, the left atrium receives oxygenated blood from the lungs and pumps it to the left ventricle, which then pumps it to the body to provide oxygen to the tissues. This continuous cycle ensures that the dog's body receives the necessary oxygen and nutrients required for proper functioning.