14 Lower Limb Nerves Flashcards
Lumbar Plexus
Is formed by the union of ant. (ventral) rami of spinal nerves L1-L4.
A part of L2 and L3 will join to form lat. cutaneous nerve of thigh that supplies the skin on the lateral side of the thigh.
The major part of L2, L3, and L4 will combine to form the femoral N. the same spinal nerves will contribute in the formation of another mixed nerve, the obturator N.
The rest of L4 joins with L5 to form the lumbosacral trunk. This trunk takes part in the formation of the sacral plexus.
Femoral Nerve
Femoral nerve (L2 – L4) emerges from the lateral side of the psoas major muscle and enters the thigh region after passing posterior to the midpoint of inguinal ligament.
It branches off in to several motor branches (for quadriceps femoris, sartorius, and pectineus) and sensory branches; anterior cutaneous branches and saphenous nerve. The anterior cutaneous branches supply the skin of anterior & medial aspects of thigh whereas the saphenous nerve supplies the skin of medial side of leg down to the base of the big toe. It is important to know that femoral nerve has sensory branches for the hip & knee joints.
Obturator Nerve
Obturator nerve (L2 – L4) emerges from the medial side of the psoas major muscle and after traveling around the pelvic inlet, passes through the obturator canal to leave the pelvis and enter the thigh region.
In thigh it supplies all the adductor muscles (Except Pectineus).
It also sends sensory branches to the hip and knee joints
Sacral Plexus
It is formed in front of the piriformis muscle by the Ant. (ventral) rami of L4 - S4 spinal nerves.
It has many sensory and motor branches for the muscles and skin of the gluteal region, post. aspect of the thigh and the whole of the leg and foot.
The largest branch of the plexus is the sciatic nerve which is formed by L4-S3 spinal nerves.
The other branches of the plexus are as follows:
Superior gluteal N.
Inferior gluteal N.
Nerve to obturator internus (and sup. Gemellus)
Nerve to quadratus femoris (and inferior gemellus)
Posterior cutaneous nerve of thigh
Pudendal nerve
Nerves of the Gluteal region
The sciatic nerve passes through the greater sciatic foramen to enter the gluteal region just inferior to the piriformis muscle. It has no branches in this area.
The posterior cutaneous nerve of thigh has a similar course and lies just medial to the sciatic nerve.
The superior gluteal nerve is a motor nerve that supplies the gluteus medius and minimus muscles and the TFL muscle.
The inferior gluteal nerve is also a pure motor nerve which supplies the gluteus maximus muscle.
Other branches of the sacral plexus in the gluteal region include the ones that supply superior & inferior Gemelli, obturator internus, and quadratus femoris muscles.
The nerve for the piriformis supplies the muscle while it is in the pelvis.
Sciatic Nerve
It is a mixed nerve, that gives motor fibres to the hamstring muscles and the posterior (ischial) head of the adductor magnus.
The sciatic nerve usually divides into two major branches as common fibular (peroneal) and tibial nerves at the distal third of the thigh.
The only muscle in the posterior compartment of the thigh, which is supplied by the common fibular (peroneal) nerve is the short head of the biceps femoris, and all other muscles are innervated by the branches from the tibial nerve.
Tibial nerve
In the popliteal fossa it is just covered by the skin and fascia.
It has some sensory branches for the knee joint. The other sensory branch is called sural nerve, which supplies the distal 2/3 of the posterior and lateral aspects of the leg.
Tibial nerve then lies between the superficial and deep layers of the muscles of the posterior compartment of leg and continues downwards between the superficial and deep layers of the muscles of the posterior compartment of leg.
Finally, after passing behind the medial malleolus, the tibial nerve enters the sole of the foot.
It supplies ALL muscles of the posterior compartment of the leg.
It also supplies the skin covering the heel.
Medial and lateral plantar nerves
Terminal branches of the tibial nerve are known as medial & lateral plantar nerves.
Medial plantar nerve supplies the skin of the medial 2/3 of the sole of the foot and also the medial 3 ½ toes. This nerve innervates the abductor hallucis, flexor hallucis brevis, flexor digitorum brevis, and the first lumbrical muscles.
Lateral plantar nerve supplies the lateral 1/3 of the sole of the foot and the lateral 1 ½ toes. It also innervates abductor digiti minimi, flexor digiti minimi, quadratus plantae, adductor hallucis, the lateral three lumbricals, and all interosseous muscles.
Common fibular (peroneal) nerve
Passes downward and laterally in the popliteal fossa. Here it has some sensory branches to the knee joint and a sensory nerve for the upper lateral side of the leg ( lateral cutaneous nerve of leg).
After turning around the neck of the fibula it lies deep to the Fibularis (peroneal) muscles and divides into the superficial and deep fibular (peroneal) nerves.
The superficial fibular (peroneal) nerve descends between fibularis (peroneus) longus and brevis muscles and innervates both of them. It then lies beneath the skin and as a sensory nerve supplies lower third of the anterior aspect of the leg and dorsum of foot.
The deep fibular (peroneal) nerve lies deep to the muscles of the anterior compartment of leg (tibialis anterior, extensor digitorum longus, and extensor hallucis longus) and innervates them. It then enters the dorsal surface of the foot to innervate extensor digitorum brevis and extensor hallucis brevis muscles. It also gives off a tiny sensory branch for the web of the big toe.
Dermatomes of the lower extremity
Cutaneous nerves of the lower extremity
Dermatomes of the sole of the foot
Lower limb myotomes
