Compartments of leg innervation
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Dermatomal distribution of lower limb from Thieme Atlas Named nerves and their cutaneous distributions from Thieme Atlas
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The lateral femoral cutaneous may be compressed where it passes beneath the inguinal ligament near the anterior superior iliac spine. The lateral femoral cutaneous nerve contributes to the L2-3 dermatomes and is sensory to the lateral thigh. The obturator nerve innervates the medial thigh muscles and is sensory for a small portion of medial thigh. The obturator nerve forms from anterior division fibers of L2-L4 and descends just medial to the psoas major muscle to pass through the obturator foramen and innervate the adductor compartment. The femoral nerve innervates the anterior thigh muscles located in the anterior compartment of the thigh. This results in wasting or weakness of the quadriceps femoris muscle and sensory impairment over the anteromedial of the thigh and medial leg (dermatomes L2, 元, and L4). It may be compressed where it passes beneath the inguinal ligament to enter the thigh. The femoral nerve forms from posterior division fibers of L2-L4 and descends just lateral to the psoas major muscle. Rotation of the upper limb bud and lower limb bud produces a change in the position of these masses relative to the body axis. We are only concerned with the named nerves of the lumbosacral plexus and their anterior or posterior spinal level contributions. Don’t worry, you don’t have to know the lumbosacral plexus to the detail that you learned the brachial plexus. The lumbosacral plexus contain branches from L1-S4. Similar to the brachial plexus that supplies the upper limb, the lumbosacral plexus supplies the lower limb. You are not expected to know the details of limb development, but the image below helps explain why the dermatomal and innervation pattern of the lower limb is distinct from the upper limb. Due to this rotation, posterior division nerves that were innervating posterior muscles in a fetus, now innervate anterior compartment muscles in a 11 mo. The lower limb rotates 180 degrees from fetal life to ~11 months. Identify the location of the sciatic nerve in terms of gluteal injections.Describe the major nerves of the lumbar plexus and sacral plexus.Describe lower limb rotation and the organization of nerves due to the limb rotation.Understand the major nerves from the lumbar and sacral plexuses and the clinical importance to the location of these nerves. Lumbosacral plexus and innervation of lower limb Key Concepts