abdomen innervation

8/4/2019 Abdomen Innervation

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Abdomen: Innervation

4-7: Abdomen: Innervation

Autonomic Nerves (Plate 318 and Plate 325)

Parasympathetic nerveso Preganglionic fibres

Provided by vagus nerve and sacral splanchnic nerves Synapse with postganglionic fibres in the walls of the relevant organs

o Vagus nerve (CN X) Give rise to anterior and posterior vagal trunks in thorax Trunks enter abdomen at the esophageal hiatus

o Anterior trunk (mainly from the left vagus) Enters anterior to the esophagus Gives branches to the anterior surface of the stomach and to the liver

o Posterior trunk (mainly from the right vagus) Enters posterior to the esophagus Gives branches to the posterior surface of the stomach and celiac plexus Fibers pass inferiorly to root of superior mesenteric artery

o Fibers contribute to perivascular plexuses Accompanying celiac and superior mesenteric artery and their branches Extend as far as the arterial supply (two thirds of the way along the transverse colon)

o Pelvic splanchnic nerves From spinal cord levels S2S4 Emerge through pelvic sacral foramina

Ascend from pelvis running in sigmoid mesocolon and peritoneum of posteriorabdominal wall

Supply distal one third of transverse colon, descending colon, sigmoid colon, andsuperior rectum

o Postganglionic (postsynaptic) parasympathetic neurons found in enteric ganglia in wall of viscus Sympathetic nerves

o Right and left sympathetic trunks Enter behind the medial arcuate ligament of the diaphragm Descend along psoas major, with right trunk behind inferior vena cava (IVC) Lie on anterolateral sides of lumbar vertebrae Receive white rami communicantes from, and send gray rami communicantes to, ventral

rami of L1

L3 spinal nerves Postganglionic fibers in gray rami communicantes to corresponding ventral rami of spinal

nerves distributed to the body wall and lower limb

Give off three to four lumbar splanchnic nerves (presynaptic sympathetic fibers) mediallyto:

Intermesenteric plexus Inferior mesenteric plexus Superior hypogastric plexus

Postsynaptic fibers from these plexuses innerves nearby target organs.o Sympathetic (paravertebral) ganglia

Total of four abdominal sympathetic ganglia per trunk


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o Prevertebral sympathetic ganglia Cell bodies of postsynapatic sympathetic neurons Found in plexuses around roots of major branches of aorta

Aortic plexuseso Network of parasympathetic and sympathetic nerves

Parasympathetic mainly from posterior vagal trunk(see above) Sympathetic fibers from thoracic and lumbar splanchnic nerves (Section 3: Thorax)

o Contain prevertebral gangliao Include:

Celiac plexus Aorticorenal plexus Renal plexus Superior mesenteric plexus Intermesenteric plexus Inferior mesenteric plexus

o Perivascular plexuses derived from the aortic plexuseso Visceral afferent fibers

Carry pain information Travel with sympathetic fibers back to spinal cord

Referred pain(Fig. 4-7-1 and Table 4-7-1)o Information carried by visceral afferent fiberso Fibers travel back to T5L2/3 spinal cord levels via thoracic and lumbar splanchnic nerveso Clinical phenomenon of referred pain is visceral pain perceived as somatic pain over the

dermatomes innervated by cutaneous nerves with fibers from those spinal cord levels.

Somatic Nerves(Plate 257, Plate 258 and Plate 267)

Thoracoabdominal nerveso Ventral primary rami of T7T11o Travel in the neurovascular plane between the internal oblique and transversus abdominis

muscleso Innervate anterolateral abdominal wall, including parietal peritoneum

Subcostal nerveso Ventral primary rami of T12o Follow the inferior border of the 12th ribo Enter abdomen behind lateral arcuate ligamentso Cross quadratus lumborum muscles and pierces transversus abdominis muscles to enter

neurovascular plane

o Innervate anterolateral abdominal wall (including parietal peritoneum) Lumbar plexus (Fig. 4-7-2)

o Iliohypogastric nerve (L1) Divides into lateral and anterior cutaneous branches Pierces internal and external oblique muscles Supplies buttocks and suprapubic region

o Ilioinguinal nerve (L1) Travels in inguinal canal Joins spermatic cord after piercing internal abdominal oblique (Note: does not enter

inguinal canal through deep inguinal ring)

Provides cutaneous branches to skin of inguinal regiono Genitofemoral nerve (L1,2)

Emerges from anterior surface of psoas major muscle Genital branch enters deep inguinal ring to innervate the cremaster muscle


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Femoral branch passes beneath inguinal ligament in vascular compartment to enterfemoral triangle and provides cutaneous branches to anteromedial thigh

o Lateral femoral cutaneous nerve (L2,3) Passes beneath or through inguinal ligament, medial to anterior superior iliac spine

(ASIS)

Innervates anterolateral thigho Obturator nerve (L2L4)

Emerges from medial border of psoas major muscle Passes through pelvis Exits via obturator canal Supplies skin and adductor muscles of medial thigh

o Femoral nerve (L2L4) Emerges from lateral psoas major muscle Innervates iliacus Passes beneath inguinal ligament on surface of iliopsoas muscle in muscular

compartment

Enters femoral triangle to innervate flexors of the hip/extensors of leg at knee, and skin ofanterior thigh, medial aspect of leg and foot.

o Lumbosacral trunk (L4,5) Enters pelvis passing over ala of sacrum Contributes to formation of sacral plexus with ventral rami of S1S4 spinal nerves

FIGURES

Plate 318: Abdomen: InnervationAutonomic Nerves and Ganglia of Abdomen

Plate 325: Abdomen: Innervation

Autonomic Reflex Pathways: Schema

Fig. 4-7-1: Visceral referred pain(Hansen JT, Lambert DR. Netter's Clinical Anatomy. Elsevier Inc., 2006,p. 447).


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Fig. 4-7-2: Diagrammatic representation of the lumbar plexus to show the origins of each of its

branches.(From Gosling JA, Harris PF, Whitmore I, et al. Human Anatomy, 4th Edition. Mosby, 2005, p. 182,

Fig. 4.100)TABLES

Table 4-7-1: Referred pain from the Abdominal Viscera

Organ Spinal Level Site of Referred Pain Netter Plate (4th edition)

Stomach T5T9 Epigastric or left hypochondrium 321

Duodenum T5T8 Epigastric or right hypochondrium

Jejunum T6T10 Periumbilical 324

Ileum T7T10 Periumbilical 324

Caecum T10T11 Periumbilical or right lower quadrant 324

Appendix T10T11 Periumbilical, then to right iliac fossa 324

Ascending colon T10T12 Periumbilical or right lumbar 324

Sigmoid colon L1L2 Left lower quadrant 324

Spleen T6T8 Left hypochondrium

Liver & gallbladder T6T9 Epigastric, later to right hypochondrium 327

Pancreas T7T9 Inferior epigastrium 328

Kidney T10L1 Small of back, flank 345

Ureter T11L1 Loin to groin 345

Note: some variation exists in the spinal levels listed

(Courtesy of Sam Yasen MBBS BSc)

FACTS & HINTS

PART A: HIGH-YIELD FACTS

Box 4-7-1: Anatomic Points

Autonomic innervation of the abdominal viscera

A perivascular plexuses of nerves accompanying the arterial supply to each organprovides autonomic innervation to the abdominal viscera.

Each plexus has sympathetic and parasympathetic input, both with motor and sensory

divisions. Motor control governs glandular secretion, smooth muscle activity, and vascular tone.

Afferent nerves mediate distension of organs and tension on mesenteries.

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abdomen innervation

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