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NERVES OF ABDOMEN Learning Objectives By the completion of lecture, the student should be able to: • • • • • Develop a basic knowledge of nerve supply of – Anterior and posterior abdominal wall. Create a visual representation of nerves supplying the abdomen. Sequence and catagorize information on the segmental sympathetic supplies and referred pain. Understand the basic structure of paravertebral plexuses. Obtain information about somatic nervous supply of abdomen. Nerve Supply of Anterolateral Abdominal Wall • • • Skin and muscles of anterior wall supplied mainly by ventral rami of inferior six thoracic nerves (i.e., the continuation of the inferior intercostal nerves, T7 to T11) and subcostal nerve (T12). Inferior part supplied by two branches of ventral ramus of first lumbar nerve via iliohypogastric and ilioinguinal nerves. Main trunks of intercostal nerves pass anteriorly from intercostal spaces and run between internal oblique and transversus abdominis muscles. Common nerve supply of the skin and the muscles of the anterolateral wall explain why palpating the abdomen with cold hands causes the muscles of the abdominal wall to contract. Nerve Supply of the Posterior Abdominal Wall • • • Psoas major: ventral rami of L1-L3 spinal nerves. Iliacus: branch of femoral nerve (L2-L3). Quadratus lumborum: ventral rami of T12, L1-L4. Abdominal Part of Oesophagus - Anterior gastric nerve contain mainly left vagal fibers. Posterior gastric nerves mainly the right vagal fibers Few sympathetic fibers from greater splanchric nerve. Nerves Of Stomach: - Derived from celiac sympathetic plexus and right and left vagus nerve. - Sympathetic innervation of stomach carries a proportion of pain transmitting nerve fibers. While parasympathetic vagal fibers are secretomotor to gastric glands and motor to muscular wall of stomach. Nerve Supply of Small Intestine • Autonomic nerves reach wall of small intestine with its blood vessel. Parasypthetic vagal suppply augments peristaltic activity and intestinal secretion. Sympathetic supply, which is vaso constrictor and normally inhibits to peristalsis is from t9 and t10 spinal segments. Nerve Supply of large intestine • • Parasympathetic N/supply to large intestine is partly from vagi and partly from pelvic splanchnic nerve. Sympathetic supply is derived from spinal cord segment t10-l2. Innervation of the Abdomen Autonomic Nervous Supply: The sympathetic supply includes: • Greater splanchnic nerve (T5-9) • Lesser splanchnic nerve (T9-10) • Lowest (least) splanchnic nerve (T12) • Lumbar splanchnic nerves (L1-3) • Sacral splanchnic nerves Autonomic Nervous Supply Cont: The parasympathetic supply includes: • • • Vagus nerve Pelvic splanchnic nerve (S2-4) These project to the paravertebral plexuses, which are situated anterior to the aorta and vertebral column. Paravertebral Plexuses Coeliac Plexus: • • • Closely related to coeliac ganglion. Lies around the origin of coeliac trunk above the upper border of pancreas and around the root of superior mesenteric artery. Plexus extends on to the crura of diaphram. The fibers making up the plexus are a follows: • • • • Preganglionic sympathetic fibers reach it through the greater and lesser splanchnic nerves. Post Ganglionic sympathetic fibers arising in the coeliac ganglion. Pre ganglionic vagal fibers are derived from posterior vagal trunk containing fibers from both the right and left vagal nerves Sensory fibers from the diaphragm reach the coeliac plexus along the inferior pherenic nerve. Phrenic Plexus: • This accompanies the inferior phrenic artery to the diaphragm and suprarenal gland. Hepatic Plexus: • • • • Largest coeliac derivative. Receives filaments from both the right and left vagus as well as from the phrenic nerves. Accompanies the hepatic artery and the portal vein and their branches and also supplies the cystic plexus to the gallbladder. Branches may also supply the pylorus, greater curvature of stomach as well as the lower bile duct, pancreatic head and 1st and 2nd part of duodenum. Left Gastric Plexus: • This goes to the lesser curvature of the stomach. • Splenic Plexus: • This is formed by branches of the coeliac plexus, left coeliac ganglion and the right vagus. • It supplies the blood vessels and smooth muscles of the splenic capsule and trabeculae. Suprarenal Plexus: • This supplies the medulla of the suprarenal gland. Renal Plexus: • This is formed by fibres from the coeliac ganglion and plexus, aorticorenal ganglion, lowest thoracic splanchnic nerves, 1st lumbar splanchnic nerve and the aortic plexus. • It gives off the ureter and gonadal plexuses (ovarian or testicular). • The ureteric plexus accompanies the ureter and the gonadal plexuses accompany the appropriate artery to the respective organs. Paravertebral Plexuses Cont: Superior Mesenteric Plexus • • This is a downward extension of the coeliac plexus. It accompanies the superior mesenteric artery to the pancreas, small intestine (duodenum, jejunum and ileum), and large intestine as far as the left trisection of the transverse colon. Abdominal Aortic Plexus (intermesenteric) This supplies the IVC, and testicular plexuses as well as connecting the superior and inferior mesenteric plexuses. Paravertebral Plexuses Cont: Inferior Mesenteric Plexus: • • This receives supply from the aortic plexus and 2nd and 3rd lumbar splanchnic nerves. It supplies the colon from the left trisection of the transverse colon to the rectum. Paravertebral Plexuses Cont: Superior Hypogastric Plexus: • • • This is situated anterior to the aortic bifurcation, L5 and the sacral promontory. This plexus is formed from branches of the aortic plexus, 3rd and 4th lumbar splanchnic nerves. It divides into the left and right hypogastric nerves, which descend to the 2 inferior hypogastric plexuses, which lie anterior to the sacrum. Inferior Hypogastric Plexus • • • • • This is formed from the pelvic splanchnic nerves (from the sacral plexus, S2-4) and also receives the sacral splanchnic nerves. Several plexuses arise from the inferior hypogastric plexuses, including: Middle rectal plexus Vesical plexus Prostatic plexus • Uterovaginal plexus. Segmental Sympathetic Supplies and Referred Pain Part Segement(s) Referred pain Oesophagus (causal part) T5-6 Retrosternal/ epigastrium Stomach T6-10 Epigastrium Small intestine (duodenum, ileum and jejunum) T9-10 Umbilical Large intestine to splenic flexure T11-L1 Umbilical Splenic flexure to rectum L1-2 Hypogastrium Liver and gallbladder T7-9 Epigastrium/right hypochondrium Segmental Sympathetic Supplies and Referred Pain Part Segement(s) Referred pain Spleen T6-10 Left hypochondrium Pancreas T6-10 Epigastrium Kidney T10-L1 Posterior lumbar Suprarenal T8-L1 Posterior lumbar Gonads T10-11 Lumbar to groin Urinary bladder T11-L2 Hypogastrium Uterus T12-L1 Hypogastrium Somatic Nervous Supply Thoracoabdominal Nerves : • • • These are branches of T6-11 intercostal nerves. They are motor to the anterolateral abdominal wall muscles, sensory to the anterolateral abdomen, gluteal region and lateral side of thigh. T10 supplies the umbilicus, T12 supplies a strip halfway between the umbilicus and pubic symphysis, T8 supplies a strip halfway between the umbilicus and xiphoid process. Somatic Nervous Supply • Phrenic Nerve: This is from C3-5 and supplies the diaphragm and related pleura and peritoneum. • Contains both motor and sensory fibres. Somatic Nervous Supply Lumbar Plexus: • • • • • • • • Extends from spinal nerves L2-4, but branches of L1 are often considered with the lumbar plexus. L4 and l5 contribute to the sacral plexus by the lumbosacral trunk. Iliohypogastric nerve (l1) Ilioinguinal nerve (l1) Genitofemoral nerve (l1-2) Lateral femoral cutaneous nerve (l2-3) Femoral nerve (l2-4) Obturator nerve (l2-4)