The sacral vertebrae are a group of five fused bones located at the base of the spine, forming the sacrum. They connect the spine to the pelvis and play a crucial role in supporting the upper body and facilitating movement. The sacrum is shaped like a triangle and helps distribute weight across the hips. Each sacral vertebra is numbered from S1 to S5, with S1 being the topmost vertebra. The fusion of these vertebrae creates a strong structure that provides stability and strength to the lower back. The sacral vertebrae also contain openings for nerves, contributing to the nervous system.