The lumbar spine anatomy contains the lower end of the spinal cord.
The spinal cord and leaves the brain and enters the spinal canal formed by the cervical vertebra. Then it passes into the thoracic spine, and in turn, into the lumbar and the sacral spine.
"the spinal cord changes into the cauda equina"
In the upper spine the spinal cord is contained within the spinal canal. As it reaches the lumbar spine, the spinal cord changes into the cauda equina, which is composed of many loose nerve roots floating in fluid within the thecal sac.
At each level of the spine there is a small opening on each side between the vertebrae called a foramen. In the upper spine nerve roots come off of the spinal cord and exit the canal through the foramen.
"each exit at the appropriate level"
In the lumbar spine, the loose nerve roots of the cauda equina, each exit at the appropriate level. They go to control your bowels and bladder, and all of the muscles, in your lower body and legs.
The spinal cord and nerves exist in very close proximity to the muscles and bones. This system works very well until things move out of place or the parts begin to wear.
A herniated disc may put disc material into the space for the nerves, or bulging discs can put pressure on nerves. Stenosis can develop, narrowing the spinal canal, or degenerative disc disease can make the discs stiff and painful, or arthritis develops in the facet joints.
"New techniques and ways of performing surgery..."
You may require surgery to remove bone or disc material that is pressing on nerve, or you may require a fusion to stabilize an area with too much mobility.
New techniques and ways of performing surgery are being developed everyday to try and find ways to rebuild, reconstruct and stabilize the spine.
"there can be problems"
The human spine is a complex structure with many moving parts, which are covered with nerve endings, and there are many opportunities for problems. The lumbar spine anatomy may be the strongest but it also gets the most abuse through a lifetime of bending and lifting, running and jumping, and twisting and falling.
Your spine does a good job of getting you through life, and allowing you to do many things, but when things go wrong there can be problems.