A new organ has been discovered hiding in plain sight inside the human body. Scientists have realized it is in fact one, continuous organ. Following its reclassification, medical students are now being taught that the mesentery is a distinct organ. The organ is a double fold of peritoneum – the lining of the abdominal cavity – that holds our intestine to the wall of our abdomen. Although there are generally considered to be five organs in the human body, there are in fact now 79, including the mesentery.