--- module: 078-01 language: en chapter: 78 title: "Abdominal Anatomy, Peritoneum, Viscera, and Portal Circulation" module_title: "Abdominal wall, inguinal region, peritoneum, mesenteries, and spaces" source_sha256: cc393a58e56566203f1c4b955abb5979eeebf174ae460646864eb3854d5114bb --- # Abdominal wall, peritoneum, and spaces ## Anterior wall and landmarks ### Costal margin to iliac crests, inguinal ligaments, symphysis ### Layers: skin to parietal peritoneum ### Camper fatty and Scarpa membranous fascia #### Membranous fascia continues into perineum #### Directs spread of urine or blood #### Thigh fascia attachment limits descent into limb ### Oblique and transverse muscle fibre directions #### Aponeuroses form rectus sheath and linea alba ### Arcuate line changes rectus sheath #### Below it all aponeuroses pass anteriorly #### Only transversalis fascia remains posterior ## Wall nerves, vessels, lymph, and incisions ### Thoracoabdominal nerves between internal oblique and transversus #### Incisions can denervate the wall ### Superior and inferior epigastric anastomosis #### Collateral flow subclavian to external iliac ### Paraumbilical veins link portal and systemic channels ### Lymph above umbilicus to axillary nodes ### Lymph below umbilicus to superficial inguinal nodes ### Midline linea alba: avascular, needs durable closure ### Transverse incision may cross segmental paths ## Posterior wall ### Vertebrae, psoas, quadratus lumborum, iliacus, diaphragm ### Lumbar plexus forms within psoas ### Retroperitoneal blood or pus irritates psoas #### Hip-flexion posture #### Femoral neuropathy ## Wall mechanics and hernias ### Muscles raise pressure with diaphragm and pelvic floor ### Pressure alone does not cause every hernia #### Fascial weakness, collagen, age, surgery, loading ### Umbilicus is a former fetal conduit ### Epigastric, umbilical, incisional, Spigelian, parastomal ### Sac, contents, neck, coverings ### Reducibility and strangulation describe risk, not type ### Rectus diastasis: no fascial defect, not a hernia ## Inguinal canal and groin hernias ### Deep ring to superficial ring, oblique course ### Anterior wall external oblique, internal oblique laterally ### Posterior wall transversalis fascia, conjoint tendon medially ### Spermatic cord or round ligament with ilioinguinal nerve #### Ilioinguinal enters laterally, not via deep ring ### Inferior epigastric vessels separate hernia types #### Indirect: lateral, via deep ring toward scrotum #### Direct: medial, through Hesselbach triangle ### Femoral hernia below ligament, medial to vein #### Narrow rigid neck, high strangulation risk ## Peritoneal layers and organ positions ### Parietal peritoneum: somatic, sharp localised pain ### Visceral peritoneum: autonomic, diffuse pain ### Intraperitoneal organs suspended by mesentery ### Primarily retroperitoneal: kidneys, adrenals, aorta, cava ### Secondarily retroperitoneal organs fused to back wall #### Duodenum, pancreas except tail, ascending, descending colon #### Fusion fascia gives avascular surgical planes ## Sacs, omenta, and mesenteries ### Lesser sac behind stomach and lesser omentum #### Pancreatic fluid can collect here ### Epiploic foramen links lesser and greater sacs #### Hepatoduodenal ligament anterior, cava posterior #### Portal triad with portal vein posterior ### Greater omentum fuses with transverse colon #### Adheres to inflammation ### Mesentery root runs duodenojejunal to ileocaecal #### Crosses duodenum, aorta, cava, right ureter ### Sigmoid mesocolon crosses left ureter ### Peritoneal ligaments are double layers, not strong #### Falciform ligament contains ligamentum teres ## Spaces, gutters, and fluid spread ### Supracolic: liver, stomach, spleen ### Hepatorenal recess dependent when supine ### Right gutter opens to hepatorenal, subphrenic spaces ### Left gutter limited by phrenicocolic ligament ### Pelvic recesses lowest when upright #### Rectovesical pouch in males #### Rectouterine pouch usually lowest in females ## Pain by embryological territory ### Foregut epigastric, midgut periumbilical ### Hindgut lower abdominal or suprapubic ### Appendicitis: periumbilical then right lower quadrant #### Parietal peritoneum involvement localises pain ### Diaphragmatic peritoneum refers to shoulder ### Posterior structures cause back pain without peritonism