Heart

The Heart is an organ that is responsible for pumping blood through the circulatory system.

In humans, the heart is usually found on the left side of the thorax, underneath a bone called the breastbone. The human heart has four chambers, a left and right atrium, and left at right ventricle. Connected to the lungs, the heart helps re-oxygenate blood before supplying it to the rest of the body.

The Vulcan heart is positioned differently than that of the human heart, located on the right side of the body underneath the lung. (Star Fleet Medical Reference Manual). Once, Captain Ronald Tracey used this fact in an attempt to prove to the people of Omega IV that Spock was the devil, and that because of this Spock had no heart. (TOS episode The Omega Glory).

The Klingon heart was, like the rest of the major organs, designed with a high degree of redundancy, having eight chambers. (TNG episode Ethics).

The heart is one of the most vital organs in a humannoid body. A serious injury to the heart can be life threatening, and hummanoids cannot live without a functional heart. By the 24th century artifical hearts were used routinely to replace hearts that quit functioning due to disease or were otherwise damaged. Captain Jean-Luc Picard's heart was replaced after he was stabbed directly though the heart by a Nausicaan during a brawl. (TNG episode Samaritan Snare). Later, when the heart of Captain Kira Neyrs was damaged by Taran'atar, Doctor Julian Bashir was unable to repair the heart, and was forced to replace it with an artificial heart. (DS9 novel Warpath).