Nerve Supply Flashcards
What is a splanchnic nerve?
Autonomic nerve, not necessarily containing parasympathetic or sympathetic fibers exclusively, could be mixed
Which plexuses supply the abdominal viscera?
The plexuses around the 3 unpaired visceral arteries, they are periarterial plexuses (nerve fibers reach viscera via blood vessels)
1) Coeliac plexus
2) Sup. mesenteric plexus
3) Inferior mesenteric plexus
Where do parasympathetic fibres originate from?
Brainstem (cranial nerves)
Sacral region of spinal cord - S2, S3, S4 (not S1 or S5)
Where do sympathetic fibres originate from?
Thoracic region of spinal cord - T1-T12
Lumbar region of the spinal cord - L1, L2, L3 (not L4/L5)
From which levels of the spinal cord do the fibres which make up the greater splanchnic nerves originate from?
T6, T7, T8, T9
From which levels of the spinal cord do the fibres which make up the lesser splanchnic nerves originate from?
T10 and T11
From which level of the spinal cord do the fibres which make up the least splanchnic nerves originate from?
T12
From which level of the spinal cord do the fibres which make up the lumbar splanchnic nerve originate from?
L1, L2, L3
What kind of fibres are carried in the greater, lesser, least and lumbar splanchnic nerves?
Sympathetic
What is the parsympathetic and sympathetic supply to the coeliac plexus which supplies the foregut?
Parasympahtetic = Vagus Sympathetic = greater splanchnic
What is the parasympathetic and sympathetic supply to the sup. mesenteric plexus which supplies the midgut?
Parasympathetic = Vagus Sympathetic = lesser and least splanchnic nerves
What is the parasympathetic and sympathetic supply to the inf. mesenteric plexus which supplies the hindgut?
Parasympathetic = pelvic splanchnic (from S2,S3,S4) Sympathetic = Lumbar splanchnic (from L1,L2,L3)
What kind of fibres run in the pelvic splanchnic nerve?
Parasympathetic
What are the 3 things which can happen to a sympathetic fibre as it leaves the spinal cord?
Sympathetic fibres originate from the lateral horn, they follow the course of the somatic efferent fibres until they jump off to travel to the sympathetic chain via the white ramus communicans they can then do 1 of 3 things:
1) Travel straight through without synapsing in the paravertebral ganglia - travel to viscera via splanchnic nerves still as pre ganglionic fibres (this is what happens to the fibres supplying the abdominal viscera!)
2) Synapse at the paravertebral ganglia and post synaptic fibres travel via the grey ramus communicans to join with the somatic nerves to supply the body wall
3) Synapse at the paravertebral ganglia and the post synaptic fibres leave the spinal cord and travel via splanchnic nerves to supply the viscera
Where do the sympathetic fibres supplying the abdominal viscera synapse?
At the prevertebral/preaortic ganglia
1) Coeliac ganglia (Either side of coeliac trunk)
2) Sup. mesenteric ganglia (either side of sup. mesenteric artery)
3) Inf. mesenteric ganglia (either side of inf mesenteric artey)
The post synaptic fibres then form the plexuses around the blood vessles
Where do parasympathetic fibres synapse?
In the gut, in the wall of the target organ, have long pre synaptic and very short post synaptic fibres
Do the coeliac and superior mesenteric plexuses communicate?
Yes
How do the superior mesenteric and inferior mesenteric plexuses communicateʔ
Via the intermesenteric plexus
What is the function of visceral afferent fibres from the gut and which route do they travel byʔ
ɢive CɴS info eg. tell the CɴS the gut is stretched and cause it to release enzymes as it has food in it
Visceral afferent nerves carrying this information travel via the parasympathetic nerves
What is a plexusʔ
Autonomic hub of mixed parasympathetic and sympathetic fibres
What is the superior hypogastric plexus, what is it formed from and where is itʔ
Sits around the bifurcation of the abdominal aorta, direct continuation of the intermesenteric plexus
What are the hypoepigastric nerves where do they originate from and what kind of fibres (mostly) do they containʔ
Originate from the superior hypoepigastric plexus - gives off a left and right hypogastric nerve which course along the internal iliac arteries (branch of common iliacs) and carry mostly sympathetic fibres
What are the inferior hypoepigastric plexuses and what is it formed fromʔ
Around internal iliacs, formed where the hypoepigastric nerves (carrying mostly sympathetic fibres) are joined by the pelvic splanchnic nerves from S2,S3,S4 carrying parasymapthetic fibres, have 2 and supply the pelvic viscera
ʜow do the pelvic splanchnic nerves reach the hind gutʔ
Either track back via the arteries or via the ɢɪ tract
ʜow do noxious (painful) stimuli travel from the abdominal viscera to the CɴS (above the sigmoid colon)
Via the sympathetic fibres
Where is pain from the abdominal viscera referred toʔ
Pain is referred to the dermatome supplied by the somatic nerves originating from the same spinal segments that the sympathetic supply of that organ originates from
eg. pain from the stomach (in foregut) is referred to the dermatom supplied by T6-T9
ʜow do noxious (painful) stimuli travel from the abdominal viscera to the CɴS (below the sigmoid colon)ʔ
Via the parasympathetic fibres (to S2-4)
What 3 things do the prevetebral (or preaortic) ganglia containʔ
1) Synapse between pre synaptic and post synaptic sympathetic fibres
2) Pre synaptic parasympathetic fibre (passes straight throuhg)
3) Afferent visceral fibres
To which dermatomes does pain from the foregut, midgut and hindgut get referredʔ
Foregutː T6-9
Midgutː T8-12
ʜindgut (before sigmoid colon)ː T12-ʟ2
Sigmoid colon downwards gets referred to S2-4 via PS fibers
In which layers of the gut wall are the myenteric plexuses located and what is there embryological origin?
Submucosal plexus in the submucosa
Myenteric plexus in the muscularis externa
Neural crest cells
At what vertebral level doe the iliohypogastric and ilioinguinal nerves come from?
Both arise from a single trunk from the anterior ramus of L1
What is the course of the iliohypogastric nerves and what do they supply?
Single trunk arises from the lateral border of the psoas major muscle which then divides into the iliohypogastric and ilioinguinal nerves
1) Iliohypogastric goes anterior to quadratus lumborum, posterior to kidney
2) Pierces the transversus abdominis and continues anteriorly around the body between the transversus abdominis and internal oblique
3) Above iliac crest gives of lateral cutaneous branch which supplies left and right internal oblique
4) Continues around body, pierces internal oblique just medial to ASIS
5) Pierces aponeurosis of external oblique just above superficial inguinal ring
Supplies branches to abdominal musculature and skin over pubic symphysis
What is the course of the ilioinguinal nerve and what does it supply?
Single trunk arises from the lateral border of the psoas muscle which then divides into iliohypogastric and ilioinguinal nerves
1) Smaller and courses more obliquely than iliohypogastric
2) Crosses iliacus on way to iliac crest, pierces transverse abdominis at anterior end of iliac crest then pierces internal oblique and into inguinal canal
3) Comes out through superficial inguinal ring and provides innervation to anterior scrotum/labia majora and skin of the groin
On course provides branches to abdo muscles
What is the nerve supply to the muscles of the anterior abdominal wall?
T7-T12 and L1 (ilioinguinal and iliohypogastric nerves)
Nb. rectus abdominis only supplied by T7-T12
What is the course of the nerves T7-T12 (subcostal nerve) which supply the muscles of the anterior abdominal wall?
1) Leave intercostal spaces passing deep to costal cartilages
2) Continue on anterolateral abdo wall between internal oblique and transversus abdominis
3) Reach lateral edge of rectus sheath, enter rectus sheath, pass posterior to the lateral aspect of rectus abdominis approaching the midline
4) Anterior cutaneous branch is given off which passes through the rectus abdominis and the anterior wall of the rectus sheath to supply the skin
The gentiofemoral nerve arises from which vertebral level and gives rise to which 2 nerves?
Arises from the anterior rami of L1 and L2
Divides into gential and femoral branches
What is the course of the genitofemoral nerve before it divides?
1) Arises from L1 and L2
2) Passes downwards in substance of psoas major until it emerges on the anterior surface of the psoas major
3) Descends on the surface of psoas major passing posterior to the ureter and then eventually dividing into genital and femoral branches
What do the 2 branches of the genitofemoral nerve supply?
Genital branch - Cremaster muscle and skin of scrotum
Femoral branch - Passes posterior to inguinal ligament supplies small region of the skin of upper anterior thigh
What is the nerve supply to the kidneys?
Renal plexuses, sympathetic from lesser and least splanchnic nerves
What are the branches called from the autonomic plexuses to the viscera and how do they travel?
Peri arterial branches, they follow the arteries
What provides autonomic input to the gonadal and ureteric plexuses?
The intermesenteric plexuses
What vertebral levels does the lateral cutaneous nerve of the thigh arise from and what does it supply?
L2-L3
Skin of anterior and lateral thigh
What vertebral levels does the obtruator nerve arise from and what does it supply?
L2-L4
Medial thigh
What vertebral level does the femoral nerve arise from, where does it enter the thigh and what does it supply?
Enters deep to inguinal ligament
Arises from L2-L4
Supplies muscles of thigh, leg and foot
What are the suprarenal glands innervated by?
Pre synaptic sympathetic fibres from lesser and least splanchnic nerves
What vertebral levels of the lumbar plexus is the psoas major supplied by?
L2-L4
What vertebral levels of the lumbar plexus is psoas minor innervated by?
L1
What vertebral levels of the lumbar plexus is quadratus
T12-L4
What vertebral level does the internal pudendal nerve come from?
S2-S4
What 2 muscles do the nerves to supply the AAW run in between?
Transversus abdominis and internal oblique
Which dermatome lies at the level of the xiphisternum?
T7
Which dermatome lies at the levels of the umbilicus?
T10
Which dermatome lies at the levels of the pubic tubercle?
L1
What arteries supply the muscles of the anterior abdominal wall?
1) Musculophrenic artery
2) Superior epigastric
3) Inferior epigastric
4) Continuation of intercostal arteries T10-T12
5) Superficial epigastric artery (from femoral artery)
