The heart and lungs are a ball and socket joint. The heart can rotate inside the lungs and the lungs can rotate around the heart.
The heart is usually approached as a separate organ that pumps blood through the rest of the circulatory system. In my experience, looking at the heart as a pump puts stress on the heart.
Many of us are unknowingly compressing the back of our heart in our effort to open the front of it. This can put pressure on the pulmonary vessels.
Embryologically, the heart begins as two tubes that join together in front of the mouth, which is above the brain at this point in development.