Hip bone each other at the pubic symphysis. Together with the sacrum and coccyx, the hip bones form the pelvis. Ilium (plural "ilia") is the uppermost and largest region. It makes up two fifths of the acetabulum. It is divisible into two parts: the body and the ala or wing of ilium; the separation is indicated on the top surface by a curved line, the arcuate line, and on the external surface by the margin of the acetabulum. The body of ilium forms the sacroiliac joint with the sacrum. The edge of the wing of ilium forms the S-shaped iliac crest which
Composition of the human body mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium. All 11 are necessary for life. The remaining elements are trace elements, of which more than a dozen are thought on the basis of good evidence to be necessary for life. All of the mass of the trace elements put together (less than 10 grams for a human body) do not add up to the body mass of magnesium, the least common of the 11 non-trace elements.