Lumbar and Sacral plexus Flashcards
Lumbar Plexus
Formed by union of Anterior (Ventral) rami of spinal nerves T12-L4
L1 Gives rise to two sensory Nerves: Iliohypogastric and ilioinguinal
Iliohypogastric supplies the skin of lower anterior abdominal wall
Ilioinguinal: Passes through inguinal canal and supplies the skin of scrotum/labia majora
Remaining part of nerve is called:
Genitofemoral nerve: Has some sensory branches for the upper medial aspect of thigh and also motor fibers for cremasteric muscle.
Lateral cutaneous nerve of thigh: L2, and L3 join to make this nerve that supplies the lateral side of the thigh
The major part of L2, L3, and L4 will combine to form the femoral N. Same spinal nerves will contribute in the formation of another mixed Nerve (Obturator Nerve)
There may be another name known as accessory obturator nerve with L3 and L4 Segments.
The rest of L4 joints with L5 to make the lumbosacral trunk. This trunk joints with sacral Plexus.
- Genital (motor) Genital branch goes to cremaster (surrounds the tests, pulls up the testis in the abdominal cavity)
- Femoral (sensory branch Femoral Triangle is supplies by femoral branch.
Meralgia Paresthetica: Compression of lateral cutaneous nerve of thigh
*to go to the lateral side of the thigh the nerve passes 1 inch medial to ASIS, and needs to dive under the InguinalLigament.Anything that increases tension to the inguinalligamentwill cause theLateralCutaneous Nerve to be pinched. Inguinalligamentwill be in tension during pregnancy, hernia, obesity, jobs that require heavy beltseipolice, and wearing tight underwear of pants
Obturator Nerve
When in the thigh region, the nerve divides to anterior and posterior branches which pass ant. and post. to the adductor brevis muscle.
These branches supply all adductor muscles and in 50% of cases the pectineus muscle is also supplied by them. There are two major sensory nerves derived from the obturator nerve which supply the hip and knee joints with somatic sensory fibers.
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 foramen to leave the pelvis and enter the thigh region.
Anterior branch = mixed nerve = motor branches supply add. Muscles EXCEPT add magnus, and obturator externus. Sensory branches reach skin of distal third of the medial side of the thigh.
Sciatic Nerve:
Mixed nerve that gives motor fibers to the hamstring muscle group and the posterior portion of adductor magnus.
Sciatic nerve usually divides into two major branches as common peroneal and tibial nerves at the distal third of the thigh.
Only muscle in posterior compartment of thigh which is supplied by common peroneal nerve in this area is the short head of the biceps femoris and all other muscles are innervated by the branches from the tibial nerve.
Tibial Nerve
Superficial nerve right under the skin
Found in the popilteal fossa it is just covered by the skin and fascia.
has some sensory branches for the knee joint mainly of proprioceptive type.
Other sensory branch is called sural nerve which supplies distal 2/3 of the posterior and lateral aspects of leg.
Nerve also supplies the superficial layer of muscles in the posterior compartment of the leg (gastrocnemius, soleus, plantaris, popliteus)
Tibial nerve then lies between the superficial and deep layers of muscles of the posterior compartment of the leg and continues downwards as it supplies (flexor hallucis longus, flexor digitorum longus, and tibialis posterior)
Finally after passing behind the medial malleolus the tibial nerve enters the sole of the foot. Just before doing that, the nerve has some sensory branches (medial calcaneal N) For the skin of the heel area.
Terminal branches of tibial nerve are known as medial and 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 1/2 toes. This nerve innervates the abductor hallucis, flexor hallucis brevis, flexor digitorum brevis, and the first three lumbrical muscles.
Lateral planar nerve supplies the lateral 1/3 of the sole of the foot and the lateral 1 1/2 toes. This nerve also innervates the abductor digitiminimi, flexor digitiminimimi, quadratus plantae, adductor hallucis, the fourth lumbrical, and all of the interosseous muscles.
Common Peroneal/Fibular Nerve
Passes downward and laterally in popliteal fossa. It has some sensory branches to the knee joint and also another 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 peroneal muscles and divides into superficial and deep branches
Upper half of the lateral side of the leg is supplied by sensory branch coming from sensory fibular = lateral sural nerve.
Superficial branch descends between peroneus longus and brevis muscles and innervates both of them. Then it lies beneath the skin and as a pure sensory nerve supplies the lower third of the anterior aspect of the leg and dorsum of the foot.
Deep branch lies deep to muscles of anterior compartment of leg. (tibialis anterior, Extensor digitorum Longus, and extensor Hallucis longus) and innervates all of them. Then the nerve 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.
Steppage gait = foot drop means common peroneal is intoxicated with lead.
Femoral nerve:
branches off into several motor branches (Quadriceps femoris, sartorius, and pectineus) and also some sensory branches (intermediate and medial cuntaenous nerves of thigh, and saphenous nerve)
These sensory branches will supply the skin of anterior and medial aspects of the thigh and also the skin of the medial side of the leg down to the base of the big toe.
It is important to know that the femoral nerve has a sensory branch of proprioceptive type for the hip joint.
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.
femoral nerve is the largest and main branch of LP its a mixed nerve.
Only branch of the femoral nerve that crosses the knee and goes to the leg.
Supllies the medial side of the leg and medial border of the foot.
Sacral Plexus
Plexus formed in front of piriformix muscle by anterior ventral rami of L4 - Co Spinal nerves.
It has so many sensory and motor branches for the muscles and the skin of gluteal region, posterior. Aspect of thigh and the whole of leg and foot.
The largest branch of the plexus is the sciatic nerve which is formed by L4-S3 spinal Nerves.
There are 4 nerves with 3 segments:
- Sup. Gluteal Nerve and Quadratus Internus N (L4, L5, S1)
- Inf. Gluteal N. and Obturator Internus N (L5, S1, S2)
- Posterior. Cutaneous Nerve of thigh (S1, S2, S3)
- Pudendal N. (S2, S3, S4)
There are 3 Nerves with 2 segments:
- Perforating cutaneous (S2, S3)
- Nerve to levator Ani (S3, S4)
Remaining parts of psinal nerves S4-Co will supply some sensory branches to the perineal and coccygeal regions.
Pudendal nerve: Mixed nerve Sensory: reaches sensory of genitalia posterior half.
Posterior Cutaneous Nerve of thigh: Pure sensory that supplies the skin in the back of the thigh
Nerves in gluteal region
Sciatic nerve passes through the greater sciatic foramen to enter the gluteal region just inferior to piriformis muscle. It is covered by a superficial layer of gluteal muscles and has no branches in this area.
Posterior cutaneous nerve of thigh has a similar course and lies just medial to the sciatic nerve.
Deep to these two and underneath Gemelli muscles, one can find nerves to quadratus femoris.
Superior Gluteal Nerve: a motor nerve and supplies: Gluteus Medius, and minimus muscles as well as the T.F.L muscle.
Inferior Gluteal Nerve: Pure motor nerve which just supplies the gluteus maximus muscle.
Pudendal Nerve: a mixed nerve which wraps around the sacro-spinous ligament and gives sensory branches to the skin of the perineal area and external genitalia as well.
Nerve to obturator internus runs superficial to obturator internus muscle
Sciatic nerve: some scientists believe that there is no sciatic nerve, its just a union of the tibial and common fibular nerve wrapped by a connective tissue…
11% of cadavers the tibial and CF are not fused and are separate causing piriformis syndrome= tibial nerve passes through piriformis and becomes compressed.
