4.a) Visceral pain

Question 1

What is the point in the enteric nervous system?

Answer 1

Enables the GI tract to perform reflex functions of secretion, absorption, mixing and gut movements without the influence of the CNS or ANS

Question 2

How is the ENS arranged?

Answer 2

In ganglionated plexuses with interconnecting bundles of unmyelinated nerve fibres

Question 3

How does the CNS communicate with the intrinsic neurones of the ENS?

Answer 3

Via sympathetic and parasympathetic nerves

Brings about modulation of GI tract functions

Question 4

What do axons of the intrinsic neurones of ENS project to?

Answer 4

Sympathetic ganglia
Pancreas
Gall bladder
Trachea
Spinal cord
Brain stem

Question 5

Where are the 2 plexuses in the GI tract?

Answer 5

Submucosal plexus: Meissner’s plexus

Myenteric plexus: Auerbach’s plexus

Question 6

Describe the distribution of the Enteric Nervous System

Answer 6

The intrinsic network of neurons of the ENS is situated in the tissues of the gut wall from oesophagus to anus.

Question 7

Where do the sympathetic nerves arise?

Answer 7

T1-L2

= Thoracolumbar

Question 8

Where do the parasympathetic nerves arise?

Answer 8

Cranial: III, VII, IX and X (occulomotor, facial, glossopharyngeal and vagus)
Sacral: S2-S4

Question 9

What are the roles of efferent autonomic nerve fibres in the abdomen?

Answer 9

Motor to smooth muscle

Secretomotor to glands

Question 10

What are the roles of afferent sympathetic and parasympathetic nerve fibres?

Answer 10

Sympathetic: mediates pain
Parasympathetic: specific functional sensation e.g. stretch

Question 11

Describe the arrangement of the splanchnic nerves.

Answer 11

All the splanchnic nerves (greater, lesser and least) arise in the thorax and descend into the abdomen.
Greater splanchnic = T5-T9
Lesser splanchnic = T10 + T11
Least splanchnic = T12

Question 12

Describe the parasympathetic innervation of organs of the

abdomen and pelvis

Answer 12

Vagus nerve (X)
Sacral outflow (S2-4)

Question 13

Describe the distribution of autonomic nerves to peripheral vessels and skin (sympathetic only)

Answer 13

Sympathetic nerves run with somatic nerves to the same region

Question 14

Describe the distribution of autonomic nerves to organs (lacking somatic innervation).

Answer 14

Most nerves run with the arteries to the same organs

There are a few cases where autonomic nerves run separately

Question 15

State the autonomic abdominal ganglia in order from top to bottom.

Answer 15

(Anterior left vagal trunk)
Coeliac trunk and ganglion 
Superior mesenteric ganglion 
Renal plexus and ganglion 
Inferior mesenteric ganglion 
Sympathetic trunk and ganglion
Superior and inferior hypogastric plexuses

Question 16

How are autonomic nerves to the abdomen routed?

Answer 16

Via plexuses surrounding the aorta and its branches

Question 17

Where do sympathetic nerves of the abdomen synapse?

Answer 17

At ganglia associated with plexuses that surround the aorta and its branches

Question 18

Where do the testicular/ovarian arteries arise?

Answer 18

Arise below the superior mesenteric artery and above the inferior mesenteric artery (closer to the SMA).

Question 19

State the nerves that travel to the organs supplied by the main branches of the aorta and the important abdominal plexuses.

Answer 19

Coeliac artery: greater splanchnic (T5-T9) + X
Superior mesenteric artery: lesser splanchnic (T10-T11) + X
Renal arteries: lesser and least splanchnic (T10-T12) + X
Testicular/Ovarian arteries: lesser splanchnic (T10-T11) + X
Inferior mesenteric artery: T12-L2 + S2-S4
Superior and inferior hypogastric plexuses: T12-L2 + S2-S4

Question 20

Why can’t the brain localise pain sensation from visceral organs and the diaphragm?

Answer 20

The cerebral cortex of the brain has no ‘sensory map’ for visceral organs and the diaphragm
Pain is referred regions of skin supplied by nerves with the same segmental supply (dermatomes)

Question 21

Dermatome

Answer 21

An area of skin supplied by a single spinal nerve (i.e. single segment of the spinal cord)

Question 22

Why might a disruption in one nerve not cause any major changes in sensation on the skin?

Answer 22

Because adjacent dermatomes overlap so that on the trunk, at least 3 spinal nerves would have to be blocked to produce a region of complete anaesthesia.

Question 23

Which vertebrae has no dermatome?

Answer 23

C1

Question 24

State the regions where pain from the foregut, midgut and hindgut is referred to
State the nerves that innervate these regions

Answer 24

Foregut: Epigastric (T7/T8)
Midgut = Umbilical (T10)
Hindgut = hypogastric (T12 - L1/2)

Question 25

What structures may cause pain in the epigastric region?

Answer 25

Stomach
Proximal duodenum
Pancreas
Liver
Gall bladder

Question 26

What structures may cause pain in the umbilical region?

Answer 26

Midgut structures (from duodenal papilla to splenic flexure) including inflamed appendix (usually colicky- intermittent with bowel contractions)

Question 27

When would pain due to an inflammed appendix be felt in the inguinal region?

Answer 27

When the inflammation spreads to the surrounding peritoneum - then the pain will become localised and constant at the right inguinal region

Question 28

What would elicit pain from an inflamed appendix?

Answer 28

Movement of the hip joint

Coughing

Question 29

What structures may cause pain in the suprapubic/ hypogastric region?

Answer 29

Hindgut structures

Descending colon to anal canal