Nerves of the posterior abdominal wall (dave's notes) Flashcards Preview

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What three nerve types make up the nerves of the posterior abdominal wall?

Somatic nerve, sympathetic nerves, and parasympathetic nerves.


What is a somatic nerve?

The somatic nervous system is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles


What is the parasympathetic nervous system?

The parasympathetic nervous system generally works to promote maintenance of the body at rest - feed and breed, rest and digest. Regulation of internal organs and glands especially at rest.


What are the three parts of the autonomic nervous system?

SNS, PSNS, and enteric nervous system.


What is a sympathetic nerve?

Mobilises the body for fight or flight response. Alongside the other two components of the autonomic nervous system, the sympathetic nervous system aids in the control of most of the body's internal organs. Stress—as in the flight-or-fight response—is thought to counteract the parasympathetic system, which generally works to promote maintenance of the body at rest. The comprehensive functions of both the parasympathetic and sympathetic nervous systems are not so straightforward, but this is a useful rule of thumb.[1][3]

There are two kinds of neurons involved in the transmission of any signal through the sympathetic system: pre- and post-ganglionic. The shorter preganglionic neurons originate from the thoracolumbar region of the spinal cord (levels T1–L2, specifically) and travel to a ganglion, often one of the paravertebral ganglia, where they synapse with a postganglionic neuron. From there, the long postganglionic neurons extend across most of the body.[4]

At the synapses within the ganglia, preganglionic neurons release acetylcholine, a neurotransmitter that activates nicotinic acetylcholine receptors on postganglionic neurons. In response to this stimulus postganglionic neurons—with two important exceptions—release norepinephrine, which activates adrenergic receptors on the peripheral target tissues. The activation of target tissue receptors causes the effects associated with the sympathetic system.[5]

The two exceptions mentioned above are postganglionic neurons of sweat glands and chromaffin cells of the adrenal medulla. Postganglionic neurons of sweat glands release acetylcholine for the activation of muscarinic receptors. Chromaffin cells of the adrenal medulla are analogous to post-ganglionic neurons; the adrenal medulla develops in tandem with the sympathetic nervous system and acts as a modified sympathetic ganglion. Within this endocrine gland, pre-ganglionic neurons synapse with chromaffin cells, stimulating the chromaffin to release norepinephrine and epinephrine directly into the blood.[6]


What is the enteric nervous system?

The enteric nervous system consists of some one hundred million neurons,[4] one thousandth of the number of neurons in the brain, and essentially equal to the one hundred million neurons in the spinal cord. [5] The enteric nervous system is embedded in the lining of the gastrointestinal system, beginning in the esophagus and extending down to the anus. [6]

The neurons of the ENS are collected into two types of ganglia: myenteric (Auerbach's) and submucosal (Meissner's) plexuses.[7] Myenteric plexuses are located between the inner and outer layers of the muscularis externa, while submucosal plexuses are located in the submucosa.


What do T12 and L1 supply?

T12 = subcostal. T12 and L2 supply the anterior abdominal wall.


List the somatic nerves found on the posterior abdominal wall

Subcostal T12
Lateral femoral cutaneous nerve
Femoral nerve
Genitofemoral nerve
Obturator nerve


What happens to L2,3,4 somatic nerves?

They break into an anterior and posterior division that then reunites to form the nerves for the flexor, extensor, and adductor compartments of the thigh.

The pass into psoas major to supply psoas and quadratus lumborum, then unite to form the lumbar plexus.


What is the thigh adductor compartment nerve?



What is the thigh flexor compartment nerve?

I don't know


What is the thigh extensor compartment nerve?

Femoral and ??LFC


What do T12 and L1 supply? What do they cross?

They cross the anterior surface of quadratus lumborum to supply the anterior abdominal wall.


What is the course of the subcostal nerve?

From the thorax to the lateral arcuate ligament it lies belos the vein and artery to rib 12, passes through transversus abdominus muscle to lie in NVP


What does T12 supply?

T12 subcostal is a large nerve supplying the anterior abdominal wall musculature, lower rectus abdominus muscle and pyrimidalis.


What supplies skin over the buttock?

The lateral cutaneous branch of T12 pierces the oblique muscles to supply the skin over the anterior part of the buttock.


Where are the iliohypogastric and iliolumbar nerves found? Where do they arise? What is their course?

They arise from L1, dividing from a common stem and pass over quadratus lumborum. They remerge from the lateral border behind the lumbar fascia and pass behind the kidney then pierce the fascia to sink into transversus abdominus muscle into the neuromuscular plane.


What gives a lateral cutaneous branch to the upper part of the buttock?

Iliohypogastric and iliolumbar.


What happens to the iliohypogastric and iliolumbar nerves once they reach the neuromuscular plane above transversus?

They slope down until piercing the aponeurosis of external oblique muscle 2.5cm above the superficial inguinal ring, and supply the skin over the lower rectus abdominus muscle and mons pubis.


What does the ilioinguinal nerve represent? What is it's course?

The collateral branch of the iliohypogastric nerve. It runs parallel at a lower level piercing the lower border of the internal oblique an entering the inguinal cal an from the side. At the superficial inguinal ring it pierces the external spernatic fascia to become subcutaneous


What supplies the anterior 1/3 of the scrotum?

The ilioinguinal nerve.


What cutaneous regions does the ilioinguinal nerve supply?

The anterior 1/3rd of the scrotum, the root of the penis, the upper and medial part of the groin.


What muscles does the ilioinguinal nerve supply?

Gives muscular branches to internal oblique muscle, transversus abdominus. These strengthen the conjoint tendon (note impt hernia).


What divisions supply the lateral femoral cutaneous nerve?

The posterior divisions of L2, L3


What is the course of the lateral femoral cutaneous nerve?

It emerges from the lateral border passing on iliacus muscle and then below the inguinal canal into thigh.


What does the lateral femoral cutaneous nerve supply?

The parietal peritoneum of the iliac fossa


What divisions supply the femoral nerve?

Posterior divisions of anterior rami of L2,3,4.


What is the course of the femoral nerve?

The femoral nerve runs down deep in the gutter between psoas and iliacus. It enters the thigh by passing below the inguinal ligament lateral to the femoral sheath.


What contributes to the genitofemoral nerve?



What is the course of the genitofemoral nerve?

The genitofemoral nerve arises on the anterior surface (of what??), running down on muscle (below fascia). Just above the ligament it perforates the fascia and divides. The genital branch passes through transversalis fascia to spermatic cord coverings with M?? to the cremasteric muscle. The femoral branch passes down in front to femoral artery supplying skin to the groin below the middle of the inguinal ligment??? check


Where does the obturator nerve emerge?

From the medial border (of what?) to enter the pelvis.


What are the two sympathetic plexi found on the posterior abdominal wall?

The lumbar and coeliac plexuses? Plexi?


What does the coeliac plexus arise from?

From the thoracic trunk.


What does the lumbar sympathetic trunk supply?

Somatic branches and pelvic viscera


What does the coeliac plexus supply? Where does it originate?

The coeliac plexus supply is entirely visceral including the gonads. It lies at the origin of the coeliac trunk.


What contributes to the lumbar sympathetic trunk?

Preganglionic fibres from the lower thoracic trunk and from L1, 2.


How do the fibres from the lower thoracic trunk reach the lumbar thoracic trunk?

They enter by passing behind the medial arcuate ligament on psoas major and the vertebral border.


Describe the lumbar sympathetic trunk

The lumbar sympathetic trunk has ganglia giving off regular somatic and visceral branches, passing down to a sacral part


Where does the lumbar sympathetic trunk lie?

The lumbar sympathetic trunk lies on the left along the aorta and on the right behind the IVC. It lies infront of the segmental vessels. Note that common iliac artery and vein (???) branches lie in front.


How many lumbar ganglia are there?

Conventionally 4.


How do somatic nerves arise from the lumbar plexus?

Somatic branches pass from lumbar ganglia to all 5 lumbar nerves (grey rami), and accompany vessels.


How do visceral branches arise from the lumbar plexus?

They arise from all lumbar ganglia to join coeliac, aortic and superior hypogastric plexuses. The 3rd and 4th loop around iliac vessels forming the superior hypogastric plexus -> IHP??? iliohypogastric plexus?


What nerves enter the coeliac plexus?

The greater and lesser splanchnic nerves. then to post ganglionic mesh of the plexus to all abdominal visceral via aortic branches.


What are the fibres of the coeliac plexus?

Motor to sphincters, vasomostor, inhibitory to peristalsis, and carry sensory from all visceral supplied.


What is special about suprarenal gland supply?

The suprarenal gland reveis a second sympathetic supply directly from one of the splanchnic nerves.


What else contributes to the coeliac plexus? How does this differ to the other contributors?

The parasympathetic nervous system has the two vagi that contribute to the coeliac plexus - without relay. These accompany the sympathetic fibres as far as the splenic flexure.


What is the function of vagus supply to the gut?

Motor, secretomotor, to gut and glands to splenic flexure.


What does the vagus not supply?

Gonads or spleen


What is the parasympathetic supply from the splenic flexure?

Pelvic splanchnic nerves.


What do the pelvic splanchnic nerves arise from?



What do the pelvic splanchnic nerves form? What do they supply?

the iliohypogastric plexus (IHP - so i think) to supply to pelvic viscera. But on the left, fibres travel up to join the IMA for gut supply.