Lecture 4 (A) - Abdominal nerves and perception of visceral pain Flashcards
(34 cards)
What is the ENS?
- Considered the brain of the gut
- Composed of more than 100million intrinsic neurones that extend the majority of the GI tract from the oesophagus to the anus
- Enable the GI tract to perform its basic reflex functions of secretion, absorption, mixing and gut movements
- Can function without the input of the CNS/ANS (although they work together to modulate GI tract function)
How is the ENS arranged?
Arranged into ganglionate plexuses with interconnecting bundles of unmyelinated nerve fibres. The axons of the intrinsic ENS neurones project to sympathetic ganglia, the pancreas, gall bladder, trachea, spinal cord and brain.
Where do sympathetic nerves arise from?
T1-L2
What do the splanchnic nerves do?
Relay visceral sensations - involved in pain.
Where do the splanchnic nerves arise from?
T5-12
Greater splanchnic nerve - T5-9
Lesser splanchnic nerve - T10-11
Least splanchnic nerve - T12
Where do parasympathetic nerves arise from?
Arises from cranial nerves 2, 7, 9 and 10 in the brainstem as well as sacral spinal cord region S2-4.
Which cranial nerves are part of the parasympathetic autonomic nervous system?
- Oculomotor
- Facial
- Glossopharyngeal
- Vagus
What is a plexus?
An interconnecting network of nerves (or vessels in some cases).
Where do autonomic nerves to the abdomen form plexuses?
Surrounding the aorta and its branches.
Where do the nerves running alongside the coeliac artery arise from?
T5-9 (S) and X (PS)
Where do the nerves running alongside the superior mesenteric artery arise from?
T10-11 (S) and X (PS)
Where do the nerves running alongside the renal arteries arise from?
T10-12 (S) and X (PS)
Where do the nerves running alongside the testicular/ovarian arteries arise from?
T10-11 (S) and X (PS)
Where do the nerves running alongside the inferior mesenteric artery arise from?
T12-L2 (S) and S2-4 (PS)
Where do the nerves forming the superior and inferior hypogastric plexuses arise from?
T12-L2 and S2-4
Why is pain relayed to regions of skin rather than the organ itself?
The cerebral cortex of the brain has no sensory map for visceral organs/diaphragm so the brain cannot localise pain sensation from these structures - instead pain is referred to regions of skin supplied by nerves of the. same segmental supply.
What is a dermatome?
An area of skin that is supplied by a single spinal cord (single segment of the spinal cord)
Where is foregut pain referred to?
The epigastric region (superior to where the organs are actually situated) associated with T7/T8 dermatomes.
What viscera are associated with epigastric pain?
- Proximal duodenum
- Stomach
- Gall bladder
- Liver
- Pancreas
Where is midgut pain referred to?
Umbilical region, which is associated with T10 dermatome.
Where is hindgut pain referred to?
Suprapubic/hypogastric pain, associated with T12/L1-2 dermatome. Movement of the hip joint and coughing can elicit pain.
How are dermatomes used for anaesthesia?
Adjacent dermatomes overlap so that on the trunk at least three spinal nerves are blocked to produce a region of complete anaesthesia.
Which spinal nerve has no dermatome?
C1
What does the abdominal aorta bifurcate into?
Common iliac arteries at L4.
