Female human anatomy cut in the sagittal plane. This computer generated image is based on segmented human data. Smooth muscle of the intestines, rectum, uterus, and bladder is visible. The cavity of the heart ventricle is surrounded by thick cardiac muscle. The heart sits on top of the diaphragm, a thin sheet of muscle that separates the thoracic cavity from the abdominal cavity. The aorta and vena cava run in front of the vertebral column.