Nerves of the posterior abdominal wall (dave's notes) Flashcards
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 L2,3,4 Iliohypogastric Iliolumbar Ilioinguinal 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?
Obturator
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
