Posterior+abdominal+wall.pdf

Abdominal dissection 2 Posterior abdominal wall and inguinal region 1) On the supine cadaver, retract the gastrointestinal tract to the side opposite that which you will be studying. You may need to continue to remove portions of the peritoneum and peritoneal/retroperitoneal fat to i...

Abdominal dissection 2 Posterior abdominal wall and inguinal region 1) On the supine cadaver, retract the gastrointestinal tract to the side opposite that which you will be studying. You may need to continue to remove portions of the peritoneum and peritoneal/retroperitoneal fat to increase the mobility of these structures. 2) Review the external and internal abdominal obliques and the transversus abdominus muscles. 3) Locate the kidney and renal artery and vein. The kidney is often covered in a considerable amount of perirenal fat. The fat can be removed fairly easily, but take care not to disrupt the ureter or related neurovascular structures. (See Gilroy, figs. 15.38A-B a) Note the ureter exiting the kidney and descending into the pelvis. After it leaves the kidney, the ureter becomes embedded in the peritoneum with or very nearby the gonadal artery and vein. (See Gilroy, figs. 16.26, 21.5) i) In the male, follow the testicular artery and vein to the deep inguinal ring. ii) In the female, follow the ovarian artery and vein to the ovary. 4) Reflect the kidney medially and identify the quadratus lumborum deep, inferior and medial to it. Review the attachments, actions, and innervation of the quadratus lumborum. (See Gilroy, figs 13.6, 13.10, 16.7) 5) Identify the psoas major muscle arising from the vertebral bodies in the lumbar spine. Also look for a thin musculotendious strip lying on the psoas major, this is the psoas minor. a) As the psoas major crosses over the iliac crest into the pelvis, the iliacus muscle can be found lateral to it. b) Review the attachments, actions, and innervation of the psoas major and iliacus muscles. 6) Palpate the 12th rib. Using your probe, carefully scrape through the transversalis fascia to find the subcostal nerve just inferior to the 12th rib. (See Gilroy, figs. 16.38, 34.11-34.16) a) Continue scraping through the transversalis fascia to find the iliohypogastric nerve. A good place to start is by estimating the height of the L1 vertebral body and to begin scraping this distance inferior to where you found the subcostal nerve. b) The ilioinguinal nerve will be just inferior to the iliohypogastric nerve. Many times, these arise from a common trunk. You may need to follow this trunk laterally to see them separate.  c) Crossing the iliacus on a diagonal from superomedial to inferolateral will be the lateral cutaneous nerve of the thigh (or lateral femoral cutaneous nerve). d) Locate the femoral nerve in the groove between the iliacus and psoas major muscles. e) The genitofemoral nerve will be lying on the anterior surface of the psoas major. Follow it inferiorly to observe its femoral and genital branches. f) Deep on the medial side of the psoas major will be the obturator nerve. The layer of peritoneum separating the abdominal viscera from the pelvic viscera may need to be removed to see the obturator nerve. g) The lumbosacral trunk can also be found medial to the psoas major, between the posterior major and the L5 vertebra. h) Review the spinal segments contained within each of these nerves. 7) In the midline of the abdomen, locate the inferior vena cava and abdominal aorta. Follow these to the bifurcation to common iliac arteries and to their respective internal and external branches. a) On the external iliac artery, find the inferior epigastric artery. Follow this to the deep surface of the rectus abdominus. Note the relationship of the inferior epigastric artery to the deep inguinal ring and to the inguinal ligament. (See Gilroy, fig. 13.15)