Lumbar ganglia

The lumbar ganglia are a group of four interconnected ganglia forming the lumbar part of the sympathetic chain. They are situated along the anterolateral surfaces of lumbar vertebral bodies, deep to the medial aspect of psoas major muscle, on either side.

Superiorly, the lumbar sympathetic chain (and its interconnected ganglia) are continuous with the thoracic sympathetic chain behind the medial crus of diaphragm, while inferiorly it descends over the ala of sacrum to continue as the sacral sympathetic chain.

The lumbar ganglia give off the following branches:

• Gray rami communicantes: Please note that all lumbar spinal nerves receive gray rami communicantes which connect the lumbar ganglia with the ventral rami of lumbar spinal nerves. The gray communicantes serve as conduits for the passage of post-ganglionic sympathetic neurons which innervate skin, vessels and sweat glands in their respective domains or could follow the nearby arterial neuronal plexuses to supply their target organs.

• White rami communicantes: Unlike the gray communicantes, the white rami communicantes emanate only form the first and second lumbar ganglia, to connect them with the ventral rami of their respective lumbar spinal nerves. The white communicantes provide passage-ways for the preganglionic sympathetic neurons, which could either synapse in the L1 and L2 lumbar ganglia or could descend in the lumbar sympathetic chain to reach out for the lower lumbar ganglia.

• Lumbar splanchnic nerves: Those preganglionic neurons, which do not synapse in the lumbar ganglia, pass un-relayed through the lumbar splanchnic nerves to reach out for various ganglia inside the nearby arterial plexuses, including coeliac, inferior mesenteric and superior hypogastric plexuses. From here onwards, post-ganglionic neurons reach out to the viscera to cause vasoconstriction, decrease glandular secretions and inhibit gastrointestinal motility.