4.a) Visceral pain Flashcards
What is the point in the enteric nervous system?
Enables the GI tract to perform reflex functions of secretion, absorption, mixing and gut movements without the influence of the CNS or ANS
How is the ENS arranged?
In ganglionated plexuses with interconnecting bundles of unmyelinated nerve fibres
How does the CNS communicate with the intrinsic neurones of the ENS?
Via sympathetic and parasympathetic nerves
Brings about modulation of GI tract functions
What do axons of the intrinsic neurones of ENS project to?
Sympathetic ganglia Pancreas Gall bladder Trachea Spinal cord Brain stem
Where are the 2 plexuses in the GI tract?
Submucosal plexus: Meissner’s plexus
Myenteric plexus: Auerbach’s plexus
Describe the distribution of the Enteric Nervous System
The intrinsic network of neurons of the ENS is situated in the tissues of the gut wall from oesophagus to anus.
Where do the sympathetic nerves arise?
T1-L2
= Thoracolumbar
Where do the parasympathetic nerves arise?
Cranial: III, VII, IX and X (occulomotor, facial, glossopharyngeal and vagus)
Sacral: S2-S4
What are the roles of efferent autonomic nerve fibres in the abdomen?
Motor to smooth muscle
Secretomotor to glands
What are the roles of afferent sympathetic and parasympathetic nerve fibres?
Sympathetic: mediates pain
Parasympathetic: specific functional sensation e.g. stretch
Describe the arrangement of the splanchnic nerves.
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
Describe the parasympathetic innervation of organs of the
abdomen and pelvis
Vagus nerve (X) Sacral outflow (S2-4)
Describe the distribution of autonomic nerves to peripheral vessels and skin (sympathetic only)
Sympathetic nerves run with somatic nerves to the same region
Describe the distribution of autonomic nerves to organs (lacking somatic innervation).
Most nerves run with the arteries to the same organs
There are a few cases where autonomic nerves run separately
State the autonomic abdominal ganglia in order from top to bottom.
(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
How are autonomic nerves to the abdomen routed?
Via plexuses surrounding the aorta and its branches
Where do sympathetic nerves of the abdomen synapse?
At ganglia associated with plexuses that surround the aorta and its branches
Where do the testicular/ovarian arteries arise?
Arise below the superior mesenteric artery and above the inferior mesenteric artery (closer to the SMA).
State the nerves that travel to the organs supplied by the main branches of the aorta and the important abdominal plexuses.
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
Why can’t the brain localise pain sensation from visceral organs and the diaphragm?
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)
Dermatome
An area of skin supplied by a single spinal nerve (i.e. single segment of the spinal cord)
Why might a disruption in one nerve not cause any major changes in sensation on the skin?
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.
Which vertebrae has no dermatome?
C1
State the regions where pain from the foregut, midgut and hindgut is referred to
State the nerves that innervate these regions
Foregut: Epigastric (T7/T8)
Midgut = Umbilical (T10)
Hindgut = hypogastric (T12 - L1/2)
What structures may cause pain in the epigastric region?
Stomach Proximal duodenum Pancreas Liver Gall bladder
What structures may cause pain in the umbilical region?
Midgut structures (from duodenal papilla to splenic flexure) including inflamed appendix (usually colicky- intermittent with bowel contractions)
When would pain due to an inflammed appendix be felt in the inguinal region?
When the inflammation spreads to the surrounding peritoneum - then the pain will become localised and constant at the right inguinal region
What would elicit pain from an inflamed appendix?
Movement of the hip joint
Coughing
What structures may cause pain in the suprapubic/ hypogastric region?
Hindgut structures
Descending colon to anal canal
