Midterm III: Lumbar + Sacral Plexus (Ben)

Question 1

What are the 6 main branches of the lumbar plexus?

Answer 1

1. Iliohypogastric n. (Th12-L1)
2. Ilioinguinal n. (Th12-L1)
3. Genitofemoral n. (L1-L2)
4. Lateral Femoral Cutaneous n. (L2-L3)
5. Femoral N. (L2-L4)
6. Obturator N. (L2-L4)

I.I.G.LF.F.O.

Question 2

What does the iliohypogastric nerve innervate?

Answer 2

Motor: Internal Oblique + Transverse Abdominal M.

Sensory: Lateral Gluteal + Lower Abd. Skin

Question 3

What does the ilioinguinal nerve innervate?

How does it get there?

Answer 3

via the inguinal canal…

male: scrotum skin
female: labia majora

Question 4

What are the two branches of the genitofemoral nerve?

Their paths?

Their innervations?

Answer 4

Genital Branch

• inguinal canal
• motor: cremaster muscle
• sensory: scrotum + genitals

Femoral Branch

• lacuna vasorum
• sensory: femoral triangle skin

Question 5

Through what does the lateral femoral cutaneous nerve travel to get to its site of innervation?

Answer 5

lacuna musculonervosa

Question 6

What are the 3 branches of the femoral nerve?

(Two are actually sets of branches.)

Answer 6

1. Rami Musculares
   
   • Quadriceps Femoris
   • Sartorius
   • Pectineus (only adductor not via obt. n.)
2. Saphenous Nerve
3. Anterior Femoral Cutaneous Branches

Question 7

What 3 muscles are innervated by the rami musculares of the femoral nerve?

(One is actually a group of muscles)

Answer 7

• Quadriceps femoris
• Sartorius
• Pectineus

Question 8

What does the saphenous nerve innervate?

Through what does it travel to get there?

Answer 8

via the adductor canal and vastoadductor membrane

it innervates the anterior lower leg

Question 9

What does the obturator nerve innervate?

Via what space?

Answer 9

adductors (except pectineus!)

via obturator canal

Question 10

What are the “two parts” of the sacral plexus?

From which spinal segments?

Answer 10

1. Sciatic Plexus (L4-S3)
2. Pudendohemorrhoidal Plexus (S3-S4)

Question 11

What part of the sciatic plexus arises from L4/L5?

Answer 11

lumbosacral trunk

• nervous tissue connecting lumbar and sacral plexuses

Question 12

What branch of the sacral plexus travels through the suprapiriform hiatus?

To innervate what?

Answer 12

Superior Gluteal Nerve

• tensor fascia latae
• gluteus medius
• gluteus minimus

Question 13

What 5 muscles do the rami musculares of the sacral plexus innervate?

Answer 13

1. Obturator Internus
2. Superior Gemelli
3. Inferior Gemelli
4. Quadratus Femoris
5. Piriformis

Question 14

What 2 branches of the sciatic plexus pass through the infrapiriform hiatus?

(note this is just the “sciatic” plexus, not the whole sacral plexus)

Answer 14

1. Sciatic Nerve
   
   • ​​(tibial + common peroneal n.)
2. Inferior Gluteal Nerve
   
   • (gluteus maximus)

Question 15

What cutaneous nerve arises from S1-S3 of the sciatic plexus?

Answer 15

Posterior Femoral Cutaneous N.

Question 16

What is the “separate” plexus arising from S3-S4?

What is its one nerve?

+ its innervated structures?

Answer 16

Pudendohemorrhoidal Plexus

Pudendal Nerve

• levator ani
• pelvic diaphragm
• pelvic viscera

Question 17

Describe the path of the pudendal nerve.

Answer 17

Leaves the infrapiriform hiatus…

Re-enters the lesser sciatic foramen…

Enters the ischiorectal fossa and travels in Alcock’s canal.