Lumbar branch of iliolumbar artery

At a glance

English

Lumbar branch of iliolumbar artery

Latin (TA2)

Ramus lumbalis arteriae iliolumbalis

System

Artery

Region

Trunk

Side

Paired, left and right

About the lumbar branch of iliolumbar artery

The iliolumbar artery normally leaves the posterior trunk of the internal iliac artery, turns up out of the pelvis and divides behind psoas major into two branches. The lumbar branch is the one that climbs; its partner, the iliacus branch, spreads into the iliac fossa. In effect the lumbar branch stands in for a fifth lumbar artery, serving the lowest lumbar segment that the aortic lumbar arteries do not reach.

It ascends behind psoas major and in front of the transverse process of the fifth lumbar vertebra, giving twigs to psoas major and to quadratus lumborum, the flat muscle of the posterior abdominal wall between the iliac crest and the twelfth rib. Along its course it links with the aorta's lowest lumbar artery, so the internal iliac and aortic segmental systems are joined at this level.

A small spinal branch leaves it and passes through the L5-S1 intervertebral foramen, where the last lumbar vertebra meets the sacrum. Inside the vertebral canal it supplies the lowest part of the canal contents, the nerve roots of the cauda equina, and the surrounding bone and coverings. This link with the vertebral canal makes the branch one of several small vessels contributing to the blood of the lumbosacral nerve roots.

Its clinical interest comes from these joins. When the internal iliac artery is tied or blocked, flow can pass between the lowest aortic lumbar artery and the iliolumbar system in either direction, helping to keep the pelvis supplied. The branch is also met in surgery at the lumbosacral junction, for example when the front of the fifth lumbar disc is approached, and when screws are placed into the sacrum or ilium.

Course and supply

Arises from

One of the two terminal branches of the iliolumbar artery, arising behind psoas major.

Ends in

Ends in muscular twigs to psoas major and quadratus lumborum, an anastomosis with the aorta's lowest lumbar artery and a spinal branch into the vertebral canal.

Supplies

Supplies psoas major, quadratus lumborum and, through its spinal branch, the cauda equina and lowest vertebral canal.