Anatomy
At birth, 5 (usually) distinct sacral bones. Fusion starts age 16-18, finished about 34. S5 is lowermost (ie apex of inverted wedge shape) and smallest segment of the fused sacrum. Laminae don’t meet (leaving a sacral hiatus); no spinous process.
Clinical
Articulates with coccyx below.
Interested in taking our award-winning Pocket Anatomy app for a test drive?
