Which of the following is NOT a function of the heart?

The selected answer is accurate because the primary functions of the heart are related to its role in circulation, which includes pumping oxygenated blood to the body, receiving blood from the lungs, and sending deoxygenated blood to the lungs for oxygenation. The heart primarily acts as a muscular pump to facilitate blood flow throughout the body and does not produce hormone signals. While the heart does communicate with other organs and systems in the body that involve hormones, it does not, as a functional role, produce hormones itself.

In contrast, the functions of pumping oxygenated blood, receiving blood from the lungs, and sending deoxygenated blood to the lungs are essential aspects of the heart's role in maintaining circulation and ensuring that tissues receive the necessary oxygen and nutrients while removing carbon dioxide. These aspects highlight the heart's involvement in the systemic and pulmonary circulatory systems. Thus, option C stands out as the function that does not directly pertain to what the heart is responsible for.