a.k.a. a lumbar puncture
spinal tap: used to obtain a sample of CSF for diagnostic purposes
spinal anesthesia: used to give anesthesia to the nerve roots of cauda equina within the dural sac (lumbar cistern); commonly used in cesarean sections
needle is inserted at L3/L4 or L4/L5
passes through ligamentum flavum
(between lamina, dura mater, and arachnoid mater