What structure of the heart receives deoxygenated blood from the muscles?

The right atrium is the structure of the heart that receives deoxygenated blood from the body, including from the muscles. This blood returns to the heart through two large veins known as the superior and inferior vena cavae. Once the deoxygenated blood enters the right atrium, it is then pumped into the right ventricle, which subsequently sends the blood to the lungs for oxygenation.

This process is crucial for maintaining proper circulation and ensuring that the body's muscles and tissues receive oxygen-rich blood after the deoxygenated blood has returned. Thus, it is the right atrium that plays a key role in collecting the deoxygenated blood returning from all parts of the body.