Anatomy of the Abdomen, Pelvis & Retroperitoneal Structures

Anatomy of the Abdomen, Pelvis & Retroperitoneal Structures Outline

z Abdomen z Layers, muscles and organs z Innervation of abdominal organs z Retroperitoneum z Structures and innervation z Pelvic Organs and innervation Abdomen Surface Anatomy of Abdomen

z Umbilicus z Linea alba = white line z Xiphoid process to pubic symphysis z Tendinous line z Inferior Boundaries z Iliac crest z Ant. Sup. Iliac spine z Inguinal ligament z Pubic crest z Superior Boundary z Diaphragm Abdominal wall Layers of abdominal wall z Fatty superficial layer - Camper’s fascia z Membranous deep layer - Scarpa’s fascia z Deep Fascial z External oblique muscle z Internal oblique muscle z Transverse abdominal muscle z Transversalis fascia z Parietal Peritoneum Muscles of Anterior Abdominal Wall

z External Obliques z O: lower 8 ribs I: aponeurosis to linea alba z Function: Flex trunk, compress abd. wall (together) Rotate trunk (separate sides) z Internal Obliques z O: Lumbar fascia, iliac crest, inguinal ligament z I: Linea alba, pubic crest, last 3-4 ribs, costal margin z Function: Same as External obliques z Transversus Abdominis z O:same as Internals, plus last 6 ribs z I: Xiphoid process, costal cart. 5-7 z Function: Compress abdomen z Rectus Abdominis z O: Pubic crest, pubic symphysis I: Xiphoid, cost cart 5-7 z Function: Flex, rotate trunk, compress abdomen, fix ribs Peritoneum z Extension of serous membrane in the abdomino-pelvic cavity z Mesentery: Double layer of peritoneum z Hold organs in place z Store fat z Route for vessels + nerves z Retroperitoneal: some organs behind peritoneum (eg) distal esophagus, duodenum, ascending + descending colon, rectum, pancreas z Peritoneal: remain surrounded by peritoneal cavity (eg) liver, stomach, ileum + jejunum, + Diaphragm z Trefoil central tendon z 5 openings z Caval z Esophageal z Aortic z Gaps for psoas m z Crus arise from lumar vertebrae z Innervation z Phrenic nerve unilaterally plus associated pleura and peritoneum z Peripheral - lower intercostal nerves Inguinal Canal Inguinal Hernias Innervation of Abdominal Organs Overview of Nerves of Abdomen

z Diaphragm z Parietal peritoneum of under surface of diaphragm supplied by phrenic nerve centrally and intercostal nerves peripherally z Stimulation centrally refers to neck and shoulder (C3 - C5) z Peripheral irritation refers to lower chest wall z Parietal Peritoneum z Somatic nerves from spinal nerves z Visceral Peritoneum z Nerves from autonomics; sensitivey similar to viscera Innervation of Viscera z Viscera normally not sensitive to painful stimuli applied to skin z Mid-esophagus to anal verge z Burn and crush not painful z Stretch, over distension, traction are normally painful z Spasm, isometric conditions, ischemia and inflammation painful Visceral Afferents and Efferents Vagus Nerves z Parasympathetic preganglionic fibers and sensory fibers to viscera of abdomen z Except left half of transverse colon and descending colon z Sacral parasympathetics z Cell bodies z Motor: dorsal motor nucleus of medulla z Sensory: inferior nodose ganglion Abdominal Splanchnics

z Lower thoracic splanchnics main source of presynaptic sympathetics to abdominal viscera z Greater: T5-T9 z Lesser: T10-T11 z Least: T12 z Pierce crus of diaphragm to reach prevertebral ganglia Abdominal Prevertebral Ganglia z Celiac Plexus z Largest prevertebral plexus z Composed of celiac ganglia and fibers z Anterior to crura of diaphragm and L1 z Anterior to abdominal aorta at level of celiac artery and root of superior mesenteric artery z Posterior to stomach, omental bursa, pancreas, portal vein and inferior vena cava z Organs innervated by fibers passing thu celiac plexus z Stomach, duodenum, jejunum, ileum, spleen, appendix, gallbladder and liver, kidneys, ureters, adrenals, ascending and transverse colon Secondary Ganglia andPlexuses from Celiac Plexus Subsidiary preverterbral ganglia z Celiac ganglia z Superior mesenteric ganglia z Inferior mesenteric ganglia z Aorticorenal ganglia z Secondary plexuses z Phrenic, gastric, hepatic, splenic, renal, superior mesenteric, intermesenteric, aortic, etc z Inferior mesenteric plexus chiefly from aortic but also from lumbar sympathetics Table of Splanchnic Nerves Autonomic Fibers and Ganglia

Key 9. Celiac trunk and ganglion 10. Superior mesenteric artery and ganglion 13. Superior hypogastric plexus and ganglion 32. Lesser splanchnic nerve 33. Lumbar splanchnic nerves 34. Sacral splanchnic nerves 35. Inferior hypogastric ganglion and plexus 37. Aorticorenal plexus and renal artery 38. Ganglion impar Abdominal Organs Esophagus, Stomach and Bowel z Distal esophagus (retroperitoneal) z Nociception via greater and lesser splanchnics (T5-9) and vagus z Stomach and duodenum

z Nociception via greater splanchnic nerves (T5-9) for stomach and T8-11 splanchnics for distal duodenum z Jejunum and ileum z Nociception via sympathetic afferents in splanchnic nerves to superior mesenteric plexus T8-12 Large intestine z Nociception to transverse colon via sympathetic

afferents from T8-12 splanchnics to superior and inferior mesenteric plexuses z Descending and sigmoid colon via superior hypogastric plexus and parasympathetic

afferents to the pelvic plexus at S2-S4 z Rectum z Superior hypogastric plexus z Note that there are some nociceptive afferents with the vagus Diagrams of Innervation of Colon Liver and Biliary Tree z Liver z Hepatic Plexus - largest derivative of celiac plexus z Biliary Ducts z Nociception via sympathetic fibers and right

splanchnic nerves from T6-10 z Vagus nerve plays no role in pain transmission z Inflammatory biliary disease stimulates afferent fibers of the parietal peritoneum causing somatic

pain in the T6-9 distribution (RUQ) Retroperitoneum

Retroperitoneal organs z Duodenum and pancreas z Ascending and descending colon z Kidneys and ureters z Bladder and uterus z Great vessels z Rectum Pancreas

z Nociception via splanchnic nerves T5-9 through celiac plexus z Vagal afferents do not mediate pancreatic pain Kidneys and Ureters z Kidneys z Lesser and least splanchnic nerves z Celiac plexus z Aorticorenal plexus z Adrenals z Greater, lesser and least slanchnics z Celiac plexus z Ureters z Nociceptive fibers with sympathetics in renal, aortic and superior and inferior hypogastric plexuses Posterior Abdomen

z Fascia removed z Ureter crosses common iliac z Vas deferens and inguinal canal z Lateral femoral cutaneous, ilioinguinal and genitofemoral n. z Celiac and mesenteric arteries Muscles of the Posterior Abdominal Wall z Psoas major

z O: Lumbar vertebrae + T12 z I: Lesser trochanter of femur via iliopsoas tendon z Function: Thigh flexion, trunk flexion, lateral flexion z Quadratus lumborum z O: iliac crest, lumbar fascia z I: trans. proc of upper lumbar vertebrae z Function: Flex vertebral column Posterior Abdominal Wall Somatic Nerves of Posterior Abdominal Wall

z Obturator (L2 - L4) z Medial border psoas z Femoral (L2- L4) z Lateral border psoas z Lumbosacral trunk z L4, L5 over sacral ala z S1-S4 sacrum z Nerves z Ilioinguinal (L1) z Iliohypogastric (L1) z Genitofemoral (L1, L2) z Lateral femoral cutaneous (L2, L3) Pelvic Organs and Innervation Pelvic Autonomics

z Superior hypogastric plexus (presacral nerve) z Contains no parasympathetics z Hypogastric nerve z Inferior hypogastric plexus z Contains parasympathetic fibers from the pelvic splanchnics z Ganglion impar Pelvic Innervation z Hypogastric Plexuses z Pelvic Splanchnics not sympathetic z Derive from ventral rami of spinal nerves (S2-S4) z Convey presynaptic parasymathetic fibers to inferior hypogastric (pelvic) plexus Pelvic Autonomics Innervation of the Bladder

z Sympathetics z T12, L1, L2 z Parasympathetics z Pelvic splanchnic nerves z Nervi erigentes z S 2, 3, 4 z Nociceptive afferents z Sacral roots (S 2, 3, 4) z Not sympathetics Innervation of Uterus, Cervix and Ovaries z Uterovaginal plexus from superior and inferior hypogastric plexuses z Sympathetic, parasympathetic and somatic afferent z Fundus and body (intraperitoneal) - Inferior and superior hypogastric plexuses z Cervix (subperitoneal) z Inferior hypogastric plexus to pelvic (splanchnic) nerves (S2-S4) (most texts) z Bonica: LUS and CX same as fundus z Ovaries - afferents with hypogastric plexuses (T10-11) Innervation of the Vagina

z Superior 3/4ths z Uterovaginal plexus z Pelvic plexus (sacral fibers) z Lower 1/4th z Pudendal nerve via sacral fibers z Perineum z Pudendal nerve Innervation of Prostate, Testes and Scrotum z Prostate z Prostatic plexus z Inferior hypogastric plexus z Testicle (T10) z Vas deferens (T10-L1) z Epididymis (T11-12) z Prostate (Prostatic plexus; similar to bladder) z Scrotum z Ilioinguinal and genitofemoral z Perineal nerve (branch of pudendal) Rectum, Anus and Perineum z Sympathetics z Superior and inferior hypogastric plexuses z Parasympathetics z Pelvic splanchnic nerves z Nociceptive afferents z Pudendal nerve (somatic) z Also with pelvic splanchnic nerves z Anus z Inferior rectal nerve via pudendal z Perineum by pudendal and branches Pudendal Nerve

z Supplies skin, organs and muscles of perineum z Distribution similar in males and females z Pudendal nerve blockade z Medial to ishial tuberosity at sacrospinous ligament z Transvaginal z Functions z Micturation z Defecation z Erection z Ejaculation z Parturition Neural Blockade of Perineum Neural Blockade for Childbirth References z Bonica’s Management of Pain. 3rd Edition, Lippincott Williams and Wilkins, 2001 z Bonica’s Management of Pain. 2nd Edition, Lippincott Williams and Wilkins, 1990 z Moore and Dalley. Clinically Oriented Anatomy, 4th Edition. Lippincott Williams and Wilkins, 1999. z Cousins and Bridenbaugh. Neural Blockade, 3rd Edition, 1998. z Raj and Patt. Pain Medicine: A Comprehensive review, 2nd Edition. Mosby, 2003.