why does a l5/s1 prolase impinge on the s1 courage root and not the l5 boldness root?

why does a l5/s1 prolase impinge on the s1 courage root and not the l5 boldness root?
The link below is the best picture I could find, sorry.
Assume the lowest lumbar is L5 contained by the diagram. You will notice that the L5 effrontery root exits BELOW the L5 pedicle but ABOVE the L5 intervertebral disc (remember in the lumbar spine the intervertebral disc and boldness are named for the verterba ABOVE it). Because of this, the L5 sassiness root is unaffected. Now look contained by the spinal canal and you will see the S1 boldness root going inferiorly and anteriorly as it will exit the S1 foramen. The prolapse occurs posteriorly and will affect the S1 gall root before it exits the spinal waterway.
Hope this helps.
Unlike contained by the cervical spinal cord, where respectively root is named for the vertebral body superior to it, within the lumbosacral spine, each is name for the vertebral body immediately inferior to it. Therefore, the S1 root is between L5 and S1 and is impinge by pathology there.
because its a fundamentally fussy nerve