**3. Healthy heart**

A healthy heart serves as the chief pumping unit of the cardiovascular system. In a healthy state, the muscular heart performs two key functions. Firstly, a healthy heart takes oxygen-depleted blood from the tissues and pumps it to the lungs, where the lungs pick up oxygen and discharge carbon dioxide. The second function of a healthy heart is to draw oxygen-rich blood from the lungs and deliver it throughout the body. The heart also removes interstitial fluid from the bloodstream and transports it to the extracellular space through systemic circulation.
