Lecture 4 (A) - Abdominal nerves and perception of visceral pain Flashcards
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.
How are the adrenals supplied with blood?
Via three main arteries:
- Superior adrenal (from inferior phrenic artery)
- Middle adrenal (from AA)
- Inferior adrenal (from renal arteries)
At what level do the gonadal arteries arise?
L2
What are common signs of an aortic aneurysm (AAA)?
- Abdominal pulsations
- Abdominal and back pain
- Compression of nerve roots causing pain or numbness in lower limbs
Where is the IVC formed?
Formed from two common iliac veins at L5, leaving the abdomen through diaphragm at T8.
What is another name for the paravertebral ganglia?
Sympathetic chain
What is another name for the prevertebral ganglia?
Distal ganglia
Describe the pathway of fibres to the abdominopelvic viscera?
Pass through the paravertebral ganglia without synapsing and then pass via the splanchnic nerves to the pre-vertebral ganglia and associated plexuses.
What do the sacral splanchnic parasympathetic nerve fibres innervate?
- Hindgut
- Kidneys and bladder
- Gonads
Where would you feel pain in cases of appendicitis?
Pain is initially defused around the umbilical region. As the appendicitis becomes more inflamed it irritates the peritoneum which is then well-localised by somatic sensory neurones.
Where would you feel pain for a stomach ulcer?
Epigastric region
