More on the sacral plexus cos i love it (dave's notes)

Question 1

How do lumbar contributions enter the sacral plexus?

Answer 1

Much of L4 and all of L5 enter the sacral pleas through the lumbosacral trunk, jointing the anterior rami of the upper four sacral nerves

Question 2

Describe the general shape, structure, and location of the sacral plexus

Answer 2

The sacral plexus is a broad triangular structure resting on priformis beneath the fascia. It gives off six branches, and then divides into anterior and posterior divisions which branch and reunite to form nerves of supply to the lower limb

Question 3

List the branches from the sacral nerves

Answer 3

Six, starting with P
Piriformis is supplied by twigs from S1,2
Perforating cutaneous nerve from S2,3, supplying skin over the buttock
Posterior femoral cutaneous nerve S2,3, supplying skin over the buttock
Parasympathetic pelvic splanchnic nerves arise from rootlets
Pudendal nerve from anterior S2,3,4
Perineal branch of S4 supplies coccygeus and levator ani and perianal skin

Question 4

List the branches from the anterior divisions of the sacral plexus. Where are they destined for?

Answer 4

Three branches destined for the flexor compartment
Sciatic, (tibial part), big branch from L4,5, S1,2,3
Nerve to obturator internus supplies this muscle and superior gemellus, leaves below piriformis
Nerve to quadratus femoris (L4,5,S1) also supplies inferior gemellus and hip joint

Question 5

List the branches from the posterior division. Where are they destined?

Answer 5

Three branches, destined for the extensor compartment
Sciatic (common peroneal) from posterior L4,5, S1,2) usually joining with the tibial part
Superior gluteal from posterior L4,5, S1 passes out above piriformis
Interior gluteal from posterior L5,S1,2 passes below prirformis

Question 6

Describe location and structure of the sacral sympathetic trunks

Answer 6

These cross the pelvic brim behind the common internal iliac artery and vein, and each characteristically has four ganglia

Question 7

What do the sacral sympathetic trunks supply?

Answer 7

These give off somatic branches to all the sacral nerves, lateral and median sacral vessels