What is the spinal level for the muscular branches to psoas & iliacus?

What is the spinal level for the muscular branches to psoas & iliacus?

• A. L2, L3
• B. L1, L2
• C. L4
• D. L3, L4

Answer: (D)

Muscular branches to psoas major and iliacus come from the lumbar plexus, so their spinal levels are the ones that contribute to motor input for these muscles. The psoas major is mainly innervated by direct branches from the ventral rami of L1–L3. The iliacus receives innervation from the femoral nerve, which arises from L2–L4. When you look at the levels that supply these two muscles’ motor branches together, L3 contributes to psoas, and L4 contributes to iliacus via the femoral nerve. That combination—L3 and L4—is why the set of spinal levels for the muscular branches to both muscles is listed as L3, L4.

Muscular branches to psoas major and iliacus come from the lumbar plexus, so their spinal levels are the ones that contribute to motor input for these muscles. The psoas major is mainly innervated by direct branches from the ventral rami of L1–L3. The iliacus receives innervation from the femoral nerve, which arises from L2–L4. When you look at the levels that supply these two muscles’ motor branches together, L3 contributes to psoas, and L4 contributes to iliacus via the femoral nerve. That combination—L3 and L4—is why the set of spinal levels for the muscular branches to both muscles is listed as L3, L4.