5 - Nerves of the Pelvis

Question 1

What is the function of somatic nerves? What do they innervate?

Answer 1

Innervate the skin and most muscles.

Mainly involved in receiving and responding to information from the external environment.

Question 2

What is the function of autonomic(visceral) nerves? What do they innervate?

Answer 2

Innervate organ systems and other visceral elements.

Detect and respond to information from the internal environment.

Sympathetic, parasympathetic, and enteric.

Question 3

How do pain afferents travel in the pelvis? How is this different from the way they travel in the abdomen?

Answer 3

In the abdomen, pain afferent retrace sympathetic pathways.

In the pelvis, they retrace parasympathetic pathways.

Question 4

What types of neurons are general somatic afferent?

Answer 4

Pseudounipolar sensory neurons.

Question 5

What type of neurons are general somatic efferent?

Answer 5

Somatic multipolar motor neurons.

Question 6

What type of neurons are general visceral efferent?

Answer 6

Autonomic multipolar motor neurons.

Question 7

In the sympathetic NS, where are the cell bodies of the post-synaptic neurons?

Answer 7

Paravertebral ganglia of the sympathetic trunks of in the prevertebral ganglia that occur in relationship to the main branches of the abdominal aorta.

Question 8

What is the path of presynaptic sympathetic fibers involved in the innervation of abdominopelvic viscera? Where do post-synaptic fibers go?

Answer 8

Pass through sympathetic trunk to prevertebral ganglia via sacral splanchnic nerves.

Post-synaptic fibers form peri-arterial plexuses that follow branches of the abdominal aorta.

Question 9

What are the two routes by which the presynaptic parasympathetic nerves exit the CNS?

Answer 9

1. Vagus nerve - cranial outflow

2. Pelvic Splanchnic nerves (S2-S4) - sacral outflow.

Question 10

What does the cranial parasympathetic outflow innervate?

Answer 10

Vagus nerve innervates the thoracic and abdominal organs (foregut to midgut) through the proximal 2/3 of transverse colon.

Question 11

What does the sacral parasympathetic outflow innervate?

Answer 11

Pelvic viscera and hindgut - distal 1/3 of transverse colon to the rectum.

Question 12

What innervates the piriformis?

Answer 12

The nerve to piriformis.

Question 13

What does the posterior cutaneous nerve of the thigh innervate?

Answer 13

Cutaneous branches to the buttocks and uppermost medial and posterior surfaces of the thigh.

Question 14

What does the perforating cutaneous nerve innervate?

Answer 14

Cutaneous branches to the medial park of the buttocks.

Question 15

What does the pudendal nerve innervate?

Answer 15

Structures in the perineum: sensory to genitalia; muscular branches to perineal muscles, external urethral sphincter, and external anal sphincter.

Question 16

What type of information does the pudendal nerve send? Why does this get confused with other nerves?

Answer 16

It sends somatic and sensory information from levels S2-S4.

The spinal levels cause some people to mistake them for parasympathetic nerves but it it NOT.

Question 17

What do the pelvic splanchnic nerves innervate?

Answer 17

Pelvic viscera via the inferior hypogastric and pelvic plexuses.

Question 18

Describe the location and nerves of the superior hypogastric plexus?

Answer 18

Located near the bifurcation of the aorta into the common iliac arteries.

Contains ONLY sympathetic fibers.

Question 19

Describe the location and nerves of the inferior hypogastric plexus?

Answer 19

Near the origin of the internal iliac artery.

Contains both sympathetic AND parasympathetic fibers.

Question 20

Describe the type of nerves that are pelvic splanchnic nerves?

Answer 20

They are ONLY parasympathetic.

Question 21

Describe the type of nerves that are sacral splanchnic nerves?

Answer 21

They are ONLY sympathetic.

Question 22

How would you determine whether a tagged nerve was pelvic splanchnic (parasympathetic) or sacral splanchnic (sympathetic)?

Answer 22

Follow it back to its origin.

Pelvic splanchnic (parasymp) nerves will go back to spinal cord segments at the S2, S3, or S4 levels.

Sacral Splanchnic (symp) nerves will lead you back to the sympathetic chain.

Question 23

Where is ureter pain referred to?

Answer 23

“Loin to groin”

Pain is from T11-L2

Question 24

What are the three locations that a kidney stone may get trapped on its way out?

Answer 24

1. Where ureter joins the renal pelvis
2. Where ureter crosses the iliac artery and pelvic brim
3. Where ureter enters bladder

Question 25

What is the pelvic pain line?

Answer 25

Make believe line above which the referred pain will retrace sympathetic routes.

Below the line pain will travel via parasympathetic pathways (pelvic splanchnic)

Question 26

If someone had a tumor on the top of their bladder, where would their pain be referred to? How do the afferents travel?

Answer 26

In the inguinal region.

The top of the bladder is above the pelvic pain line so the pain would retrace sympathetic pathways.

Question 27

If someone has pain in their lower bladder, where is the pain referred to? What symptoms might this patient experience?

Answer 27

Lower portion of bladder is below pelvic pain line and therefore retraces parasympathetic pathways and be referred to S2-4, which is right back to where the pain started.

Saddle pain from signals being sent out through the pudendal nerve.

Question 28

What is the pectinate line?

Answer 28

Landmark between the somatic and visceral innervation of the anal canal.

Above: visceral innervation relatively insensitive to pain

Below: somatic innervation that’s sensitive to pain and is under voluntary control.

Question 29

Describe the blood flow, innervation, and lymphatics above the pectinate line?

Answer 29

Nerves: visceral motor (mixed symp and parasymp) and sensory innervation

Arteries: IMA
Veins: Portal system

Lymphatics: internal iliac nodes

Question 30

Describe the blood flow, innervation, and lymphatics below the pectinate line?

Answer 30

Nerves: Somatic motor and sensory innervation.

Arteries: Internal iliac a.
Veins: Caval system

Lymphatics: Superficial inguinal nodes

Question 31

Describe the innervation of the vagina?

Answer 31

Proximal 3/4 is the visceral tissue innervated by the parasympathetics (pain via pelvic splanchnic)

Distal 1/4 is somatic via the pudendal nerve

Question 32

Describe the innervation of the uterus above the cervical (pelvic pain) line? What does this tell us about pain from the uterus?

Answer 32

Sympathetic innervation.

Pain travels via sympathetic pathways: uterovaginal and pelvic plexuses, hypogastric plexus: lower aortic plexus, lumbar splanchnic nerves, and the sympathetic trunk.

Question 33

How does pain from the cervix and upper vagina travel? What about from the lower vagina?

Answer 33

Cervis and upper vagina: via pelvic splanchnic nerves to S2, S3, and S4.

Lower vagina and perineum: via the pudendal nerves to S2, S3, and S4.

Question 34

What is the benefit of performing a spinal block via a lumbar puncture as opposed to a caudal epidural black or a pudendal nerve block?

Answer 34

Anesthesia travels such that it knocks out the sensation from the uterus, the nerves into the pelvis (S2-S4), and the pudendal nerve.

This effectively anesthetizes the uterus, the cervix and proximal vagina, and the distal vagina.

Question 35

Where does pain visceral pain from the testis get referred to?

Answer 35

The lower thoracic region.

Question 36

What are the branches of the pudendal nerve?

Answer 36

The inferior anal nerve

Perineal nerve - gives off posterior labial or posterior scrotal nerve superficially and the deep perineal nerve

Question 37

What causes voluntary relaxation of the external urethral sphincter? What happens?

Answer 37

Somatic efferents.

Bladder empties.

Question 38

What happens when voiding is done? What controls this?

Answer 38

The detrusor muscle relaxes and the external sphincter contracts.

Sympathetic control.

Question 39

What happens when voiding is done in males?

Answer 39

The bulbospongiosus muscle contracts to expel the last few drops from the spongy urethra.

Detrusor muscle relaxes under sympathetic control.

Question 40

What is the path of the pudendal nerve?

Answer 40

Passes through the greater sciatic foramen

Question 41

if you see pelvic roots, what is the muscle you’re looking at underneath them? What is beneath them? Lateral to them?

Answer 41

The piriformis.

Below them that is the coccygeus.

Lateral is the obturator internus.

Question 42

How do you tell if something from S2-4 is a pelvic splanchnic or a pudendal nerve?

Answer 42

Pelvic splanchnics come off S2-4 and doesn’t seem to be going to a structure .

Question 43

Where is the internal pudendal artery found (ie what is it near)?

Answer 43

Internal pudendal artery near inferior gluteal artery but smaller.

Question 44

How do sympathetics arrive in the pelvis?

Answer 44

Through the hypogastric plexus and the sacral splanchnics (shot through sympathetic trunk).

Hypogastric nerves come from the superior hypogastric which is just parasympathetic.

Question 45

Where do sacral splanchnics emerge?

Answer 45

Sacral portion of sympathetic trunk.