The legs are affected by a complex network of nerves, primarily originating from the lumbar and sacral plexuses. Here's a breakdown of the major nerves involved:
Major Nerves Affecting the Legs:
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Femoral Nerve: The femoral nerve is one of the largest nerves in the leg. It arises from the lumbar plexus (L2-L4 nerve roots).
- Function: It provides motor function to the hip flexors (muscles that bend the hip) and knee extensors (muscles that straighten the knee) and sensory function to the front and inner thigh and part of the lower leg and foot.
- Area Affected: Anterior thigh, medial leg, and foot.
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Sciatic Nerve: The sciatic nerve is the largest and longest nerve in the human body. It originates from the sacral plexus (L4-S3 nerve roots). In the thigh, it splits into the tibial and common fibular (peroneal) nerves.
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Function: It controls muscles in the back of the thigh, lower leg, and foot. It also provides sensation to the back of the thigh, part of the lower leg, and the entire foot.
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Area Affected: Posterior thigh, lower leg, and foot.
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Tibial Nerve (branch of sciatic):
- Function: Provides motor function to the muscles in the back of the lower leg and sole of the foot (plantarflexion and toe flexion). Sensory function to the sole of the foot.
- Area Affected: Posterior lower leg, sole of the foot.
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Common Fibular (Peroneal) Nerve (branch of sciatic): This nerve further divides into the superficial and deep fibular nerves.
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Function: Provides motor function to muscles that dorsiflex (lift) the foot and evert (turn outward) the foot. Sensory function to the lateral lower leg and dorsum (top) of the foot.
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Area Affected: Lateral lower leg, dorsum of the foot.
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Superficial Fibular (Peroneal) Nerve: Supplies the muscles on the lateral compartment of the leg and sensation to the lower lateral leg and most of the dorsum of the foot.
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Deep Fibular (Peroneal) Nerve: Supplies the muscles of the anterior compartment of the leg and provides sensation between the big toe and second toe. It assists in dorsiflexion of the foot.
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Other Nerves Contributing:
- Obturator Nerve: Arises from the lumbar plexus (L2-L4). Provides motor function to the adductor muscles of the thigh (muscles that bring the legs towards the midline) and sensory function to the inner thigh.
- Lateral Femoral Cutaneous Nerve: Arises from the lumbar plexus (L2-L3). Provides sensation to the outer thigh.
Summary:
The legs' function and sensation rely on a network of nerves arising from the lumbar and sacral plexuses. The femoral and sciatic nerves, along with their branches, are the primary nerves affecting the legs, controlling movement and providing sensation. The obturator and lateral femoral cutaneous nerves also contribute to thigh function and sensation.
