A heart is an organ that pumps blood via the circulatory system to the rest of the body. The heart is a marvelously crafted muscular pump and in humans, the heart of an embryo begins beating 21 days after conception. According to the Bible the heart is the seat for our deepest emotions and wishes. Change in personality has been noted in Heart transplant survivors consistent with this.
Heart is situated inside the thorax in vertebrates and in human body is slightly to the left. Human heart consists of 4 main chambres, 2 atria and 2 ventricles. The right side of the heart receives blood from the body and pumps it to the lungs where it is oxygenated and returns to the left side of the heart. The left side of the heart pumps the oxygen carrying blood to the rest of the body.