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Anatomy > Lumbosacral Plexus > Flashcards

Lumbosacral Plexus Flashcards

1
Q

plexus

A

-valuable because it helps maintain some level of function even if one or two segments damaged, muscle may be weak but you wont lose full function

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2
Q

lumbar plexus

A
  • anterior thigh
  • provides sensation and motor innervation to anterior and medial thigh
  • plexus is formed by anterior primary rami of L1-L4
  • branches of lumbar plexus supply motor and sensory innervation to lower anterior abdominal wall and supplies all motor and sensory innervation to anterior thigh
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3
Q

abdomen

A

everything below 12th rib and above inguinal ligament

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4
Q

quadratus lumborum

A
  • attaches 12th rib to illiac crest

- forms planar surface in posterior abdomen

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5
Q

psoas major

A
  • passes out of abdominal region and into the thigh
  • 1/2 of the lumbar nerves emerge from lateral border of psoas major
  • lumbar plexus built within this muscle
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6
Q

psoas minor

A
  • doesn’t leave pelvic cavity

- makes attachment on pelvic bone and has no effect on lower extremities

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7
Q

Muscle and Joint Relationship

A
  • a muscle that crosses a joint will have action on that joint
  • if muscle doesn’t cross the joint it can’t have action on the joint
  • ex: psoas major crosses hip joint so it becomes major hip flexor
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8
Q

Subcostal Nerve

A
  • passes inferior border of 12th rib

- origin: T12

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9
Q

Iliohypogastric Nerve

A

-origin: L1 upper

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10
Q

Ilioinguinal Nerve

A

-origin: L1 upper

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11
Q

Genitofemoral Nerve

A
  • runs on anterior surface of psoas major
  • 2 parts: genital and femoral
  • origin: L1 lower, L2 upper
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12
Q

Lateral Femoral Cutaneous Nerve

A
  • lateral border of psoas major
  • ascend angling up toward the ASIS
  • origin: L2, L3
  • supply to skin of lateral thigh
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13
Q

Femoral Nerve

A
  • biggest of lumbar plexus nerves
  • origin: Post Div L2, L3, L4
  • nerve of knee extension and contribute to thigh flexion
  • small branches can come off nerve and dive into iliacus muscle
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14
Q

Obturator Nerve

A
  • deep, medial border of psoas major
  • passes through obturator canal and hangs in space
  • origin: Ant Div L2 lower, L3, L4
  • special case: even though it is anterior division, it doesn’t provide flexors
  • contributes to adductor compartment, medial thigh
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15
Q

Lumbosacral Trunk

A
  • passes over pelvic brim and dives into true pelvis and into sacral plexus
  • origin: L4, L5
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16
Q

Rotation of Developing Limbs- Anterior and Posterior Compartments

A
  • body is mostly flat until rotation of limbs occurs at 6-8 weeks
  • upper extremities rotate laterally
  • lower extremities rotate medially
  • UE: anterior, preaxial, flexor
  • LE: posterior, postaxial, flexor (anterior is extensors)
  • if muscles are in flexor compartment, you know they have to come from anterior divisions
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17
Q

anterior primary rami

A

-anterior divisions of spinal nerve as it emerges from intervertebral frame

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18
Q

White and Gray Rami

A
  • L1-L4: white and gray rami, communications between the spinal nerve and sympathetic ganglion
  • L5: only gray rami
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19
Q

Upper and Lower Branches

A

-give us blending of roots

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20
Q

Lumbosacral Supply: Subcostal N (T12)

A
  • crosses quadratus lumborum
  • pierces transversus abdominal (deepest abdominal layer) and runs in plane between transversus abdominal and internal oblique like intercostal nerves
  • most inferior of nerves that run with ribs
  • innervation of intercostal passes distally across quadratus lumborum
  • sensory to skin halfway between umbilicus and pubis
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21
Q

Lumbosacral Supply: Iliohypogastric Nerve

A
  • crosses QL posterior to kidney, ascends toward iliac cres, pierces TA and runs in plane between TA and IO like intercostal nerves
  • anterior and lateral cutaneous branches communicate with branches of ilioinguinal nerve
  • sensory to skin above pubis
22
Q

Lumbosacral Supply: Ilioinguinal Nerve

A
  • crosses QL posterior to kidney, ascends toward iliac cres, pierces TA and runs in plane between TA and IO like intercostal nerves
  • communicates with anterior cutaneous branches of iliohypogastric nerve
  • sensory to skin above pubis and motor to interior abd obl
  • passes along inguinal ligament
  • descends with (not within) spermatic cord to supply skin of upper medial thigh, scrotum, and root of penis
23
Q

Lumbosacral Supply: Genitofemoral Nerve

A
  • descends on anterior surface of psoas major
  • acts like 2 nerves (genital branch and femoral branch)
  • external spermatic nerve is genital portion and descends within spermatic cord and supplies cremaster muscle
  • lumboinguinal nerve is femoral branch and distributes to thigh
  • cremaster reflex: stroke upper, medial thigh produces contraction of cremaster muscle and elevation of testis which tests for proper innervation and function of L1, L2
24
Q

Lumbosacral Supply: Lateral Femoral Cutaneous Nerve

A
  • crosses illiacus muscle and ascends towards ASIS

- distributers to skin of anterior, lateral, and posterior thigh down to the knee

25
Q

Lumbosacral Supply: Femoral Nerve

A
  • largest lumbar plexus branch
  • emerges from lower lateral border of psoas major and descends on iliacus, supplying it
  • descends under inguinal ligament into Femoral Triangle
  • broad motor supply of anterior thigh muscles: pectineus, sartorius, quadriceps, femoris
  • supplies skin of anterior thigh
  • SAPHENOUS NERVE: descends through wall of adductor canal and distributes sensation to medial leg down to root of great toe, only branch that extends below knee from lumbar plexus, purely cutaneous
26
Q

Lumbosacral Supply: Obturator Nerve

A
  • emerges from medial border of psoas major, passing posterior to illiac vessels and ureter along lateral wall of pelvis to enter obturator canal
    -enters medial thigh under fibers of obturator externus muscle and divides into:
    1. Anterior branch that decends on anterior surface
    of adductor brevis behind pectineus, supplies
    adductor brevis and longus and gracilis and ends
    as cutaneous n to skin of medial thigh, superficial
    2. Posterior branch that usually pierces substance of
    obturator externus muscle to distribute to adductor
    magnus, sometimes add brevis, and ends as
    articular branches to knee
27
Q

Nerves/ Dermatomes and Sensory Tests

A
  • dermatomes are named after nerve root
  • cremaster reflex: tests sensory and motor functions of L1, L2
  • patellar tendon reflex: tests sensory (input) and motor functions (output) of L2,3,4
  • medial malleolus: test sensory function of L4
  • dermatomes are most reliable in the hands
  • sensory testing landmarks
28
Q

L2,3,4 Posterior Division- Femoral Nerve

A

-motor innervation of anterior thigh: iliacus, sartorius, rectus femoris, vastus lateralis, vastus intermedius, vastus medialis, pectineus (can also be innervated by obturator nerve)

29
Q

L2,3,4 Anterior Division- Obturator Nerve

A

-motor innervation of medial thigh: pectineus, adductor brevis, adductor longus, gracilis, adductor magnus, and obturator externus

30
Q

Sacral Plexus

A
  • L4/5- S4
  • connected to lumbar plexus through lumbosacral trunk (some L4/5)
  • branches of sacral plexus supply motor and sensory innervation to posterior thigh, all of sensory innervation of leg except strip supplied by saphenous nerve and foot, and supplies all motor to the leg and foot
31
Q

sacral plexus roots

A
  • ventral (anterior) rami L5-S4 with smaller contribution from L4
  • L4-L5 contribution descends into pelvis as lumbosacral trunk
  • 5 major branches, each root leaves pelvic cavity
32
Q

Superior Gluteal Nerve

A
  • L4, L5, S1
  • exits the pelvis through greater sciatic foramen (more significant)
  • enters the gluteal region above piriformis muscle (key to gluteal region, ext rotator of femur, organizing muscle)
  • passes distally in plane between the gluteus medius and minimus
  • accompanied by superior gluteal veins
  • motor supply to glut med, glut min, and tensor fascia lata
33
Q

Inferior Gluteal Nerve

A
  • L5, S1, S2
  • exits pelvis through greater sciatic foramen
  • enters gluteal region inferior to piriformis
  • accompanied by inferior gluteal veins
  • motor supply to gluteus max
34
Q

Sciatic Nerve

A
  • L4, L5, S1, S2, S3
  • 2 divisions: Tibial Nerve (anterior division, L4- S3) and Common Fibular Nerve (posterior division, L4-S2)
  • sensory supply to most of leg except by saphenous
  • exits the pelvis through greater sciatic foramen; enters the gluteal region below piriformis
35
Q

True hamstring vs NOT true hamstring

A
  • true hamstring has tibial nerve as its supply
  • true hamstring has proximal attachment on ischial tuberosity and distal attachment below knee
  • Biceps femoris long head is true hamstring, short head is not either of these
36
Q

Tibial Division of Sciatic Nerve

A
  • motor supply to muscles of posterior thigh (except Biceps femoris short head), posterior leg, and foot flexors
37
Q

Common Fibular Division of Sciatic Nerve

A
  • motor supply to anterior and lateral leg (except biceps femoris long head) and to foot extensors
38
Q

Composite Muscle

A
  • ex: Biceps Femoris
  • part of it is true hamstring supplied by tibial nerve, the other part is not but its insertion is through a common tendon
39
Q

Pudenal Nerve

A
  • sensory, motor big automatic function sexually
  • S2, S3, S4
  • leaves the pelvis via the greater sciatic for amen, then re-enters vi the lesser sciatic foramen because nerves established early on in development
  • crosses anterosuperiorly along lateral wall of ischiorectal fossa and terminates by dividing into several branches
  • sensory supply to penis and clitoris and most skin of perineum
  • motor supply to perineal muscles, external urethral sphincter, external anal sphincter, and levator ani
40
Q

Posterior Femoral Cutaneous Nerve

A
  • S1, S2, S3
  • large parts of skin provided by peripheral nerves
  • Arises partly from posterior divisions of S1 and S2 and anterior divisions of S2 and S3
  • exits pelvis through greater sciatic foramen and enters gluteal region inferior to piriformis
  • accompanied by inferior gluteal nerves and vessels deep to glut max
  • passes over long head of biceps femoris and descends to back of knee, supplying branches to posterior thigh
  • emit inferior cluneal branches under lower border of glut max to supply lower lateral buttocks
  • emits perineal branches to supply perineum, scrotum, and labia majora
41
Q

Nerve to Piriformis

A
  • L5, S1, S2
  • never leaves the pelvis
  • supplies piriformis muscle from anterior surface
42
Q

Nerve to Obturator Internus and Superior Gemellus Muscle AND Nerve to Quadratus Femoris and Gemellus Inferior Muscle

A
  • leaves pelvis via greater sciatic foramen to supply those muscles
  • small nerves that supply external rotators
43
Q

2 Sacral Plexus Nerves Contribute to Sciatic Nerve

A

Tibial Nerve- L4, L5,S1,S2,S3 and
Find slide 25 and write out
-only part of posterior thigh that is not supplied by tibial nerve is biceps femoris short head
- pre axial flexor muscles are supplied by anterior tibial nerve and plantar muscles in the foot (flex toe)
- common fibular nerve branches to supply muscles in lateral and posterior department which is extension and Dorsiflexion
-medial part of leg is not supplied by sacral plexus

44
Q

Origin of Sacral Plexus

A

-lumbosacral trunk is most medial and posterior, flattened tightly on surface of pelvic brim

45
Q

Superior gluteal artery and nerve

A

Gap between lumbosacral trunk (L4, L5) and S1

46
Q

Inferior gluteal artery

A

-In between S2 and S3

47
Q

Sciatic Nerve

A
  • bundle of L4- S3

- piriformis serves as base for all of weaving of sacral plexus

48
Q

Greater Sciatic Foramen

A
  • most nerves exit through here

- tucks behind coccygeus muscle (pelvic floor) and in front of piriformis as the exit into gluteal region

49
Q

Tendinous Arch

A

-attachment for obturator internus

50
Q

Sacral Plexus in Sagittal Plane

A
  • gap between ilium and ischial spine creates the greater sciatic foramen
  • gap between ischial spine and ischium is lesser sciatic foramen
  • exits above piriformis: superior gluteal nerve supplies motor to glut med, glut min, and TFL
  • exits below piriformis: everything else, sciatic, posterior femoral, inferior gluteal
  • pudenal exits greater sciatic and renters lesser sciatic

Anatomy (8 decks)

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