The human heart resembles a conical shape, similar to an upside-down pear. It has four chambers: two upper atria and two lower ventricles. This unique structure allows the heart to function effectively as a muscular pump that circulates blood throughout the body. The heart's external surface features a network of blood vessels, including the aorta and pulmonary arteries, and is encased in a protective sac known as the pericardium. The heart is also asymmetrical, with the left side generally being more muscular due to its role in pumping oxygenated blood to the entire body, while the right side pumps deoxygenated blood to the lungs.