Unit 2: Lecture 18 (Lumbosacral Plexus)

Question 1

Muscles lining the posterior abdominal wall

Answer 1

psoas major
iliacus
quadratus lumborum
psoas minor (40% of ppl)

Question 2

endoabdominal/transversalis fascia

Answer 2

connective tissue lining the muscles of the posterior abdominal wall and the entire internal surface of that wall

• continuous with endopelvic fascia
• invested with fat (preperitoneal fat)

Question 3

What APR form lumbar plexus

Answer 3

L1-L4, T12 (50% of time)

Question 4

Gray rami communicantes (sympathetic postganglionics) from the sympathetic trunk enter which roots?

Answer 4

T12-L4

Question 5

Which roots send White rami communicantes (sympathetic preganglionics) to the sympathetic trunk

Answer 5

T12-L2

Question 6

Within what muscle does the lumbar plexus form?

Answer 6

Psoas major

-emerges from lateral, anterior, and medial borders

Question 7

Nerves of Lumbar Plexus

Answer 7

subcostal nerve (T12)
iliohypogastric (L1)
ilioinguinal (L1)
genitofemoral (L1-L2)
lateral femoral cutaneous (L2-L3)
femoral (L2-L4)
obturator (L2-L4)
accessory obturator (L3-L4) (9% of ppl)

Question 8

divisions of lumbar plexus

Answer 8

anterior and posterior

Question 9

posterior division of lumbar plexus includes what nerves

Answer 9

lateral femoral cutaneous n

femoral n

Question 10

anterior division of lumbar plexus

Answer 10

obturator n and accessory n’s

Question 11

What VPR make up sacral plexus

Answer 11

L4-S3, and part of S4, all nerves derived from Ant or Post Divisions/Branches

Question 12

Sacral plexus lies anterior to the _________ muscle, on the _______ ________ wall.

Answer 12

piriformis muscle

posterior pelvic wall

Question 13

Divisions/Branches of sacral plexus

Answer 13

anterior and posterior

Question 14

Branches from the sacral plexus pass to lower limb through the _______ ________ ________

Answer 14

greater sciatic foramen

Question 15

Nerves/branches of sacral plexus

Answer 15

Superior gluteal n (L4, L5, S1)
Inferior gluteal n (L5, S1, S2)
sciatic n (L4-S3)
Nerve to quadratus femoris muscle and gemellus inferior (L4-S1)
Nerve to obturator internus and gemellus superior (L5-S2)
Posterior cutaneous n's to thigh (S2,S3)
pudendal n (S2-S4)
Nerve to piriformis (S1-S2)
pelvic splanchnic nerves (S2-S4)

Question 16

Anterior division of sacral plexus includes what nerves

Answer 16

**Tibial N (L4-L5, S1-S3)
**Posterior Femoral Cutaneous (S2-S3)
**Pudendal n (S2-S4)
N to quadratus femoris and gemellus inferior
N to obturator internus and gemellus superior
Pelvic Splanchnic n
Perineal branch of 4th sacral n
Nerve to levator ani.

Question 17

Posterior division of sacral plexus includes what nerves

Answer 17

**Common peroneal n (L4-L5, S1-S2)
**posterior femoral cutaneous n (S1-S2)
superior gluteal n
inferior gluteal n
N to piriformis
Perforating cutaneous n

Question 18

Landmarks of the posterior abdominal wall

Answer 18

Two, 12th ribs
Lumbar spine
Ilium and Iliac crest
Iliacus
Psoas major

Question 19

Deep to transversalis fascia

Answer 19

• preperitoneal fat

- peritoneal lining- lines the abdomen and supports abdominal viscers

Question 20

What connects L4-L5 VPR to S1 VPR

Answer 20

Lumbosacral trunk

Question 21

Sciatic nerve made up of which 2 nerves

Answer 21

common fibular/peroneal and tibial n’s, which split when approaching popliteal fossa