Vertebral Column

Sacrum

The sacrum is formed by a fusion of the bodies and processes of three vertebrae.  It lies between the ilia and firmly articulates with them.  The dorsal surface presents several markings that result form the fusion of the three sacral vertebrae.  The median sacral crest represents the fusion of the three spinous processes.  Found also on the dorsal surface are two pairs of dorsal sacral foramina, which transmit the dorsal branches of the first two sacral spinal nerves.  Found on the pelvic, or ventral surface are two pairs of pelvic sacral foramina, which transmit the ventral branches of the first two sacral spinal nerves.