The sacrum is a bone containing the five sacral vertebrae.
Location of the sacrum
The sacrum is located in the vertebral column, lying vertically between the lumbar vertebrae and the coccyx and horizontally between the two iliac bones of the pelvis.
Structure of the sacrum
The sacrum is a paired, mid-line symmetrical bone formed by the fusion of the five sacral vertebrae. Being an inverse pyramid in shape, it can lie in the pelvis and close it. Its superior surface is called the sacral promontory and its inferior surface is called the apex.
Function of the sacrum
Because of its anatomical position with respect to the sexual organs, the sacrum exhibits sexual dimorphism. It is shorter but wider in women than in men.
The sacrum is part of the vertebral column. © Uwe Gille, Wikimedia, public domain