Retroperitoneum

• Abdominal aorta


  Begins at the aortic hiatus of the diaphragm as a midline structure at approximately the lower level of vertebra TXII<|>Passes downward on the anterior surface of the bodies of vertebrae LI to LIV<|>Ends just to the left of midline at the lower level of vertebra LIV<|>Divides into the right and left common iliac arteries
• The bifurcation of the abdominal aorta can be visualized on the anterior abdominal wall as a point approximately 2.5 cm below the umbilicus or even with a line extending between the highest points of the iliac crest
• Abdominal aorta


  • The prevertebral plexus of nerves and ganglia covers its anterior surface as it passes through the posterior abdominal region
• Branches of the abdominal aorta

  • Celiac trunk
  • Superior mesenteric artery
  • Inferior mesenteric artery
  • Middle suprarenal arteries
  • Renal arteries
  • Testicular or ovarian arteries
  • Inferior phrenic arteries
  • Lumbar arteries
  • Median sacral arteries
  • Common iliac arteries
• Celiac trunk


  Arises immediately inferior to the aortic hiatus of the diaphragm<|>Supplies the abdominal foregut
• Superior mesenteric artery


  Arises immediately inferior to the celiac trunk<|>Supplies the abdominal midgut
• Inferior mesenteric artery


  Arises inferior to the renal arteries<|>Supplies the abdominal hindgut
• Middle suprarenal arteries


  Arise immediately superior to the renal arteries<|>Supply the suprarenal glands
• Renal arteries


  Arise immediately inferior to the superior mesenteric artery<|>Supply the kidneys
• Testicular or ovarian arteries

  Arise in pairs from the anterior aspect of the abdominal aorta inferior to the renal arteries<|>Supply the testes in males and ovaries in females
• Inferior phrenic arteries


  Arise immediately inferior to the aortic hiatus<|>Supply the diaphragm
• Lumbar arteries


  Usually arise in four pairs from the posterior aspect of the abdominal aorta<|>Supply the posterior abdominal wall and spinal cord
• Median sacral arteries


  Arise just superior to the aortic bifurcation<|>Pass inferiorly across the lumbar vertebrae, sacrum, and coccyx
• Common iliac arteries


  Terminal branches of the abdominal aorta<|>Bifurcation usually occurs at the level of the LIV vertebra
• Inferior vena cava


  Returns blood from all structures below the diaphragm to the right atrium of the heart<|>Formed by the union of the two common iliac veins at the level of vertebra LV just to the right of midline<|>Ascends through the posterior abdominal region anterior to the vertebral column immediately to the right of the abdominal aorta<|>Leaves the abdomen by piercing the central tendon of the diaphragm at the level of vertebra TVIII
• Inferior vena cava


  • Crossed anteriorly by the right common iliac artery, the root of the mesentery, the right testicular or ovarian artery, the inferior part of the duodenum, the head of the pancreas, the superior part of the duodenum, the bile duct, the portal vein, and the liver, which overlaps and on occasion completely surrounds the vena cava
• Lumbar veins


  The fifth lumbar vein generally drains into the iliolumbar vein, a tributary of the common iliac vein<|>The third and fourth lumbar veins usually drain into the inferior vena cava<|>The first and second lumbar veins may empty into the ascending lumbar veins
• Ascending lumbar veins


  Long, anastomosing venous channels that connect the external iliac, iliolumbar, and lumbar veins with the azygos and hemiazygos veins of the thorax<|>Become important collateral channels between the lower and upper parts of the body if the inferior vena cava becomes blocked
• Spinal nerves


  • Iliohypogastric
  • Ilio-inguinal
  • Genitofemoral
  • Lateral cutaneous nerve of thigh
  • Obturator
  • Femoral
• Iliohypogastric nerve


  Arises from the anterior ramus of L1<|>Supplies the internal oblique and transversus abdominis muscles<|>Provides sensory innervation to the posterolateral gluteal skin and skin in the pubic region
• Ilio-inguinal nerve


  Arises from the anterior ramus of L1<|>Supplies the internal oblique and transversus abdominis muscles<|>Provides sensory innervation to the skin in the upper medial thigh, and either the skin over the root of the penis and anterior scrotum or the mons pubis and labium majus
• Genitofemoral nerve


  Arises from the anterior rami of L1 and L2<|>Genital branch supplies the cremasteric muscle in males or skin of the mons pubis and labium majus in females<|>Femoral branch supplies skin of the upper anterior thigh
• Lateral cutaneous nerve of thigh

  Arises from the anterior rami of L2 and L3<|>Supplies skin on the anterior and lateral thigh to the knee
• Obturator nerve


  Arises from the anterior rami of L2 to L4<|>Supplies the obturator externus, pectineus, and muscles in the medial compartment of the thigh<|>Provides sensory innervation to the skin on the medial aspect of the thigh
• Femoral nerve


  Arises from the anterior rami of L2 to L4<|>Supplies the iliacus, pectineus, and muscles in the anterior compartment of the thigh<|>Provides sensory innervation to the skin on the anterior thigh and medial surface of the leg