Anatomy of the Abdomen, Pelvis & Retroperitoneal

Structures

Outline

AbdomenLayers, muscles and organs

Innervation of abdominal organsRetroperitoneum

Structures and innervationPelvic Organs and innervation

Abdomen

Surface Anatomy of AbdomenUmbilicus Linea alba = white line

Xiphoid process to pubic symphysisTendinous line

Inferior BoundariesIliac crestAnt. Sup. Iliac spineInguinal ligamentPubic crest

Superior BoundaryDiaphragm

Abdominal wall

Layers of abdominal wall

Fatty superficial layer - Camper’s fasciaMembranous deep layer - Scarpa’s fasciaDeep Fascial

External oblique muscleInternal oblique muscleTransverse abdominal muscle

Transversalis fasciaParietal Peritoneum

Muscles of Anterior Abdominal WallExternal Obliques

O: lower 8 ribs I: aponeurosis to linea albaFunction: Flex trunk, compress abd. wall (together)

Rotate trunk (separate sides)Internal Obliques

O: Lumbar fascia, iliac crest, inguinal ligamentI: Linea alba, pubic crest, last 3-4 ribs, costal marginFunction: Same as External obliques

Transversus AbdominisO:same as Internals, plus last 6 ribsI: Xiphoid process, costal cart. 5-7Function: Compress abdomen

Rectus AbdominisO: Pubic crest, pubic symphysis I: Xiphoid, cost cart 5-7Function: Flex, rotate trunk, compress abdomen, fix ribs

Peritoneum Extension of serous membrane in the abdomino-pelvic cavityMesentery: Double layer of peritoneum

Hold organs in placeStore fatRoute for vessels + nerves

Retroperitoneal: some organs behind peritoneum (eg) distal esophagus, duodenum, ascending + descending colon, rectum, pancreasPeritoneal: remain surrounded by peritoneal cavity (eg) liver, stomach, ileum + jejunum, +

DiaphragmTrefoil central tendon5 openings

CavalEsophagealAorticGaps for psoas m

Crus arise from lumar vertebraeInnervation

Phrenic nerve unilaterally plus associated pleura and peritoneumPeripheral - lower intercostal nerves

Inguinal Canal

Inguinal Hernias

Innervation of Abdominal Organs

Overview of Nerves of AbdomenDiaphragm

Parietal peritoneum of under surface of diaphragm supplied by phrenic nerve centrally and intercostal nerves peripherallyStimulation centrally refers to neck and shoulder (C3 - C5)Peripheral irritation refers to lower chest wall

Parietal PeritoneumSomatic nerves from spinal nerves

Visceral PeritoneumNerves from autonomics; sensitivey similar to viscera

Innervation of Viscera

Viscera normally not sensitive to painful stimuli applied to skin

Mid-esophagus to anal vergeBurn and crush not painfulStretch, over distension, traction are normally painfulSpasm, isometric conditions, ischemia and inflammation painful

Visceral Afferents and Efferents

Vagus Nerves

Parasympathetic preganglionic fibers and sensory fibers to viscera of abdomenExcept left half of transverse colon and descending colonSacral parasympatheticsCell bodies

Motor: dorsal motor nucleus of medullaSensory: inferior nodose ganglion

Abdominal Splanchnics

Lower thoracic splanchnics main source of presynaptic sympathetics to abdominal viscera

Greater: T5-T9Lesser: T10-T11Least: T12

Pierce crus of diaphragm to reach prevertebral ganglia

Abdominal Prevertebral GangliaCeliac Plexus

Largest prevertebral plexusComposed of celiac ganglia and fibersAnterior to crura of diaphragm and L1Anterior to abdominal aorta at level of celiac artery and root of superior mesenteric arteryPosterior to stomach, omental bursa, pancreas, portal vein and inferior vena cava

Organs innervated by fibers passing thu celiac plexusStomach, duodenum, jejunum, ileum, spleen, appendix, gallbladder and liver, kidneys, ureters, adrenals, ascending and transverse colon

Secondary Ganglia andPlexusesfrom Celiac Plexus

Subsidiary preverterbral gangliaCeliac gangliaSuperior mesenteric gangliaInferior mesenteric ganglia Aorticorenal gangliaSecondary plexuses

Phrenic, gastric, hepatic, splenic, renal, superior mesenteric, intermesenteric, aortic, etcInferior mesenteric plexus chiefly from aortic but also from lumbar sympathetics

Table of Splanchnic Nerves

Autonomic Fibers and GangliaKey9. Celiac trunk and ganglion10. Superior mesenteric artery and

ganglion13. Superior hypogastric plexus and

ganglion32. Lesser splanchnic nerve33. Lumbar splanchnic nerves34. Sacral splanchnic nerves35. Inferior hypogastric ganglion and

plexus37. Aorticorenal plexus and renal

artery38. Ganglion impar

Abdominal Organs

Esophagus, Stomach and Bowel

Distal esophagus (retroperitoneal)Nociception via greater and lesser splanchnics (T5-9) and vagus

Stomach and duodenumNociception via greater splanchnic nerves (T5-9) for stomach and T8-11 splanchnics for distal duodenum

Jejunum and ileumNociception via sympathetic afferents in splanchnic nerves to superior mesenteric plexus T8-12

Large intestine

Nociception to transverse colon via sympathetic afferents from T8-12 splanchnics to superior and inferior mesenteric plexusesDescending and sigmoid colon via superior hypogastric plexus and parasympathetic afferents to the pelvic plexus at S2-S4

RectumSuperior hypogastric plexus

Note that there are some nociceptive afferents with the vagus

Diagrams of Innervation of Colon

Liver and Biliary TreeLiver

Hepatic Plexus - largest derivative of celiac plexusBiliary Ducts

Nociception via sympathetic fibers and right splanchnic nerves from T6-10

Vagus nerve plays no role in pain transmissionInflammatory biliary disease stimulates afferent fibers of the parietal peritoneum causing somatic pain in the T6-9 distribution (RUQ)

RetroperitoneumRetroperitoneal organs

Duodenum and pancreasAscending and descending colonKidneys and uretersBladder and uterusGreat vesselsRectum

Pancreas

Nociception via splanchnic nerves T5-9 through celiac plexusVagal afferents do not mediate pancreatic pain

Kidneys and UretersKidneys

Lesser and least splanchnic nervesCeliac plexusAorticorenal plexus

AdrenalsGreater, lesser and least slanchnicsCeliac plexus

UretersNociceptive fibers with sympathetics in renal, aortic and superior and inferior hypogastric plexuses

Posterior Abdomen

Fascia removedUreter crosses common iliacVas deferens and inguinal canalLateral femoral cutaneous, ilioinguinaland genitofemoral n.Celiac and mesenteric arteries

Muscles of the Posterior Abdominal Wall

Psoas majorO: Lumbar vertebrae + T12

I: Lesser trochanter of femur via iliopsoas tendonFunction: Thigh flexion, trunk flexion, lateral flexion

Quadratus lumborumO: iliac crest, lumbar fascia I: trans. proc of upper lumbar vertebrae

Function: Flex vertebral column

Posterior Abdominal Wall

Somatic Nerves of Posterior Abdominal WallObturator (L2 - L4)

Medial border psoasFemoral (L2- L4)

Lateral border psoasLumbosacral trunk

L4, L5 over sacral alaS1-S4 sacrum

NervesIlioinguinal (L1)Iliohypogastric (L1)Genitofemoral (L1, L2)Lateral femoral cutaneous (L2, L3)

Pelvic Organs and Innervation

Pelvic Autonomics

Superior hypogastric plexus (presacral nerve)Contains no parasympathetics

Hypogastric nerveInferior hypogastric plexus

Contains parasympathetic fibers from the pelvic splanchnics

Ganglion impar

Pelvic InnervationHypogastric PlexusesPelvic Splanchnics not sympatheticDerive from ventral rami of spinal nerves (S2-S4)Convey presynapticparasymathetic fibers to inferior hypogastric(pelvic) plexus

Pelvic Autonomics

Innervation of the Bladder

SympatheticsT12, L1, L2

ParasympatheticsPelvic splanchnic nervesNervi erigentesS 2, 3, 4

Nociceptive afferentsSacral roots (S 2, 3, 4)Not sympathetics

Innervation of Uterus, Cervix and Ovaries

Uterovaginal plexus from superior and inferior hypogastric plexuses

Sympathetic, parasympathetic and somatic afferentFundus and body (intraperitoneal) - Inferior and superior hypogastric plexusesCervix (subperitoneal)

Inferior hypogastric plexus to pelvic (splanchnic) nerves (S2-S4) (most texts)Bonica: LUS and CX same as fundus

Ovaries - afferents with hypogastric plexuses (T10-11)

Innervation of the Vagina

Superior 3/4thsUterovaginal plexusPelvic plexus (sacral fibers)

Lower 1/4thPudendal nerve via sacral fibers

PerineumPudendal nerve

Innervation of Prostate, Testes and Scrotum

ProstateProstatic plexusInferior hypogastric plexus

Testicle (T10)Vas deferens (T10-L1) Epididymis (T11-12)Prostate (Prostatic plexus; similar to bladder)Scrotum

Ilioinguinal and genitofemoralPerineal nerve (branch of pudendal)

Rectum, Anus and PerineumSympathetics

Superior and inferior hypogastric plexusesParasympathetics

Pelvic splanchnic nervesNociceptive afferents

Pudendal nerve (somatic)Also with pelvic splanchnic nerves

AnusInferior rectal nerve via pudendal

Perineum by pudendal and branches

Pudendal NerveSupplies skin, organs and muscles of perineumDistribution similar in males and femalesPudendal nerve blockade

Medial to ishial tuberosityat sacrospinous ligamentTransvaginal

FunctionsMicturationDefecationErectionEjaculationParturition

Neural Blockade of Perineum

Neural Blockade for Childbirth

ReferencesBonica’s Management of Pain. 3rd Edition, Lippincott Williams and Wilkins, 2001Bonica’s Management of Pain. 2nd Edition, Lippincott Williams and Wilkins, 1990Moore and Dalley. Clinically Oriented Anatomy, 4th Edition. Lippincott Williams and Wilkins, 1999.Cousins and Bridenbaugh. Neural Blockade, 3rd Edition, 1998.Raj and Patt. Pain Medicine: A Comprehensive review, 2nd Edition. Mosby, 2003.