Nerves of Pelvis and Perineum

Question 1

What is the pudendal nerve?

Answer 1

Major somatic nerve of the sacral plexus

Question 2

What are the roots of the pudendal nerve?

Answer 2

S2-S4 (arises from ventral rami)

Question 3

What are the motor/sensory functions of the pudendal nerve?

Answer 3

Motor - innervates various pelvic muscles, the external urethral sphincter and the external anal sphincter.

Sensory - innervates the external genitalia of both sexes and the skin around the anus, anal canal and perineum

Question 4

Describe course of pudendal nerve from pelvis to perineum

Answer 4

Leaves pelvis via greater sciatic foramen and crosses sacrospinous ligament. Enters perineum via lesser sciatic foramen.

Question 5

Describe course of pudendal nerve after re-entering perineum

Answer 5

After re-entering the pelvis, it accompanies the internal pudendal artery and vein, coursing anterosuperiorly through the pudendal canal. Inside the pudendal canal, the nerve divides into branches.

Question 6

What is the pudendal canal also known as?

Answer 6

Alcock’s canal

Question 7

What is the pudendal canal formed by?

Answer 7

Formed by fascia of obturator internus muscle

Question 8

What branches does the pudendal nerve give off?

Answer 8

1. Inferior rectal nerve
2. Perineal nerve
3. Continues as dorsal nerve of penis/clitoris

Question 9

What does the pudendal canal contain?

Answer 9

Pudendal nerve, internal pudendal artery, pudendal veins

Question 10

Where does perineal branch pass?

Answer 10

Travels superficial to the urogenital diaphragm

Question 11

Describe motor function of pudendal nerve

Answer 11

The pudendal nerve provides the voluntary/somatic control of faecal and urinary continence.

Perineal nerve:

• Levator ani muscles
• Bulbospongiosus (muscle overlying corpus spongiosum)
• Ischiocavernosus (muscle overlying corpus cavernosum)
• External urethral sphincter

Inferior rectal:
- External anal sphincter

Question 12

What are levator ani muscles innervated by?

Answer 12

• Perineal nerve

- Direct innervation from anterior ramus of S4 nerve root

Question 13

Describe sensory function of pudendal nerve

Answer 13

The pudendal nerve supplies sensation to external genitalia of both sexes and the skin around the anus, anal canal and perineum through its branches (inferior rectal, perineal, dorsal nerve of penis or clitoris)

Question 14

What does inferior rectal branch innervate?

Answer 14

Innervates the perianal skin and lower third of the anal canal.

Question 15

What does perineal nerve innervate?

Answer 15

Innervates the skin of the perineum, labia minora and majora or scrotum.

Question 16

What does dorsal nerve of penis or clitoris innervate?

Answer 16

Innervates the skin of the penis or clitoris. Thus, responsible for the afferent component of penile and clitoral erection.

Question 17

What is a pudendal nerve block?

Answer 17

A form of analgesia occasionally given before vaginal childbirth, episiotomy and other minor vaginal procedures.

Local anaesthetic is then injected into the tissues around the ischial spine (on each side)

Question 18

Where is the site of pudendal nerve block?

Answer 18

Ischial spine

Question 19

What provides sensory innervation of external genitalia?

Answer 19

• Ilioinguinal nerve
• Genital branch
• Perineal branch
• Posterior cutaenous nerve of thigh

Question 20

Nerves project inferiorly from sympathetic chain to form what plexus?

Answer 20

Braid of nerves –> superior hypogastric plexus

Question 21

What is the superior hypogastric plexus comprised mainly of?

Answer 21

Sympathetic fibres

Question 22

How do sympathetic fibres enter pelvis? What then forms?

Answer 22

Project either side via left and right hypogastric nerve into pelvis

Forms another network of nerves within pelvis –> inferior hypogastric plexus

This network is joined by pelvic splanchnic nerves (parasympathetic)

Question 23

What does the inferior hypogastric plexus consist of?

Answer 23

Combination of sympathetic and parasympathetic fibres

Question 24

Where do sympathetic fibres of inferior hypogastric plexus come from?

Answer 24

Superior hypogastric plexus

Question 25

Where do parasympathetic fibres of inferior hypogastric plexus come from?

Answer 25

Pelvic splanchnic nerves

Question 26

How does sympathetic innervation reach pelvis?

Answer 26

Through superior hypogastric plexus (and right and left hypogastric nerves)