The human tailbone and sacrum can be felt as it continues up the anus. The sacrum is a less regular bone that looks more like a triangle-like bone, flanked by the iliac bones. The sacrum and ilium of the body then form the sacroiliac joint, with an articular surface to the left and right of the sacroiliac head. By flattening the anus slightly upward horizontally, a harder bone can be felt along the sides in the middle of the muscle, and this bone is the sciatic tuberosity. The sciatic tuberosity is also a part of the sciatic bone, and other parts of the sciatic bone cannot be felt by hand. From the anus of the human body upwards, you can feel two iliac bones, two sit bones, a sacrum, a coccyx, from the human body of these bones form the rear part of the human pelvis. Follow the human body above the sacrum is the vertebrae belonging to the lumbar spine, and upward is the bone around the hip.