Sectioned foetus. Sagittal section through a 16 week old female foetus, revealing the internal organs. At this stage it measures around 14 centimetres from head to rump. The brain (white) is surrounded by the still soft bones of the skull. The spinal cord runs from the brain, down through the vertebrae of the backbone. The bladder is the large sac to the left of the leg. Other abdominal organs are seen around it, including the intestines and the liver (large, triangular, just below arm). The lungs are not yet fully developed as the foetus would have obtained oxygenated blood from its mother.