Now we head on up to the second lumbar segment. The second lumbar segment is very interesting as it is primarily in charge of the evacuation functions as well as some reproductive functions. I will explain those points soon.
The nerves associated with the second lumbar segment are: the femoral nerve (L2-L4), obturator nerve (L2-L4), lateral femoral cutaneous nerve (L2-L3), and the genitofemoral nerve (L1-L2). The recurrent meningeal nerve as well as segmental branches to local spinal muscles are also present.
The important muscles to recognize as related to the second lumbar segment are the psoas major and minor, the quadratus lumborum, the longissimus thoracis, multifidus, and rotatores. Due to the primarily sagittal nature of the second lumbar vertebrae the majority of movement potential in the segment is flexion and extension while the psoas and quadratus lumborum will often provide coronal lesions (side-bending) due to contraction/relaxation of the muscles.
Now to speak about the reproductive organs. In men the genitofemoral nerve is responsible for the sensation to the inner thigh and scrotum while also being in charge of the cremaster muscle. The cremaster is primarily responsible for the position of the testicles to promote temperature regulation to control spermatogenesis. In women the cremaster muscle is not fully developed however it does exist as attached to the round ligament. If there is an inhibitory lesion to the genitofemoral nerve (in Marion Clark’s words, specifically the nutrient nerve to the round ligament) the round ligament will relax and the uterus will no longer be held in anteversion. For men with low sperm counts or other testicular issues the second lumbar segment may be a reasonable place to look for a lesion.
The rectum and the bladder also receive control from the second lumbar segment. If there is a lesion to the second lumbar segment there will either be excessive or limited defecation or urination. There are also nerve filaments to the hypogastric plexus meaning that the second lumbar segment has a lot of influence over evacuation of the digestive tract.
To reiterate the fact that the second lumbar segment displays primarily flexion and extension is worthwhile. It should be noted that a flexed segment provides a larger intervertebral foramen with associated increases in arterial supply that will lead to excitement of the exiting nerves where extension will decrease the intervertebral foramen and inhibit the exiting segments. Bearing the previous statement in mind it is easily understood that excessive evacuation (defecation or urination and even menstruation) will be associated with a flexed segment while inhibited evacuation will be associated with an extended segment. To balance an evacuation issue the second lumbar segment should be returned to normal function so that the intervertebral foramen do not alter evacuation functions. The same can be said for testicular issues in males as the cremaster needs to function properly to promote proper spermatogenesis.
Due to the musculature available (primarily the psoas, quadratus lumborum, and the erector musculature) and the location of the second lumbar segment (fairly distant from the limbs) long lever correction in any position provides very powerful correction options directly to the second lumbar segment. Think around the table and use the limbs to get to the second lumbar segment to create correction with minimal effort.