Lumbar plexus

A network of nerves that provides motor and sensory innervation to parts of the lower back, pelvis, and lower limb.

The lumbar plexus is a major nerve network located in the lumbar region of the spine. It is formed by the anterior rami of the first four lumbar spinal nerves (L1-L4), with contributions from the subcostal nerve (T12). This plexus is responsible for supplying nerves to the lower abdominal wall and the anterior and medial aspects of the thigh, as well as providing sensory innervation to the skin in these areas.

Terminologia Anatomica

plexus-lumbalis

System

Nervous system

Function

The primary role of the lumbar plexus is to facilitate movement and sensation in the lower body. It contributes to the formation of several important nerves, including the femoral nerve, which innervates the quadriceps muscle, allowing for knee extension, and the obturator nerve, which is responsible for inner thigh adduction. Additionally, the lumbar plexus supports the genitofemoral nerve, which provides sensation to the groin area, and the lateral femoral cutaneous nerve, supplying the skin on the outer thigh. The plexus' intricate network ensures that electrical signals for motor control and sensory feedback travel efficiently between the central nervous system and the lower limbs, which is paramount for activities such as walking, running, sitting, and maintaining balance.

Location

The lumbar plexus is located in the posterior abdominal wall, emerging from the region of the lumbar vertebrae. It is situated deep within the psoas major muscle, a large muscle that runs vertically along the lumbar spine to the pelvis. The plexus typically resides between the transverse processes of the lumbar vertebrae and extends laterally to the iliacus muscle. The peripheral nerves that branch out from the plexus then travel downward into the pelvic region and thigh, following specific paths to reach their target muscles and skin areas. Its position allows it to effectively connect the spinal cord to the various distal structures in the lower body, enabling efficient communication of nervous signals.

Did You Know?

The lumbar plexus is sometimes referred to as the 'lumbosacral plexus' because it connects with the sacral plexus in the pelvis.
Damage to the lumbar plexus can lead to conditions such as foot drop or weakness in the thigh muscles.
The lumbar plexus is involved in reflex actions, such as the knee-jerk reflex, which is tested during physical examinations.