is simply another word for the vertebral column
, and is an abbreviation of spinal column. It constitutes, therefore, a bony column made up of vertebra one on top of another, joined by fibrous intervertebral discs. The lumbar vertebra constitute five vertebra progressing from the middle of the back, where the thoracic cage ends, to where it joins with the pelvis
. It forms an extension of the thoracic vertebra
above and meets the sacral vertebra, or sacrum, below. The thoracic vertebra are more or less stiff and rigid, ensuring the essential function of supporting the entire spinal column. The natural curve of the lumbar vertebra is called lordosis
and, as with the rest of the vertebral column, it protects the spinal cord and the nerves produced from it, which here are essentially those that innervate the lower limbs.