The medial branches of the posterior divisions of the lumbar nerves run close to the articular processes of the vertebræ and end in the Multifidus.
The lateral branches supply the Sacrospinalis.
The upper three give off cutaneous nerves which pierce the aponeurosis of the Latissimus dorsi at the lateral border of the Sacrospinalis and descend across the posterior part of the iliac crest to the skin of the buttock, some of their twigs running as far as the level of the greater trochanter.
The anterior divisions of the lumbar nerves (rami anteriores) increase in size from above downward.
The first and second, and sometimes the third and fourth lumbar nerves are each connected with the lumbar part of the sympathetic trunk by a white ramus communicans.
The first three and the greater part of the fourth are connected together in this situation by anastomotic loops, and form the lumbar plexus.
The fourth nerve is named the nervus furcalis, from the fact that it is subdivided between the two plexuses.