A physician orders a lumbar puncture (spinal tap) for his 43…

A physician orders a lumbar puncture (spinal tap) for his 43-year-old female patient in order to obtain a sample of cerebrospinal fluid (CSF) to diagnose bacterial versus viral meningitis. He explains to her that this procedure will be done in the lower back, between the spinous processes of the L3 and L4 vertebrae. What is the anatomical basis for performing the lumbar puncture at this location?