Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
UNIT 24. DISSECTION: ANTERIOR ABDOMINAL WALL STRUCTURES TO IDENTIFY: Linea alba Superficial epigastric artery External oblique Transverse abdominis Rectus sheath Superior epigastric artery Deep circumflex iliac artery Deep inguinal ring Medial crural fibers Intercrural fibers Pectineal ligament Spermatic cord Iliohypogastric nerve Ductus (vas) deferens Pampiniform venous plexus Superficial circumflex iliac artery Internal oblique Rectus abdominis Transversalis fascia Inferior epigastric artery Superficial inguinal ring inguinal ligament Round ligament Ilioinguinal nerve Scrotum Testes Epididymus Testicular vessels DISSECTION INSTRUCTIONS: 1. First incision: A mid-line incision 3 mm deep from the xiphoid process to the symphysis pubis, circling the umbilicus. Second incision: An incision 1 cm below the inguinal ligament from the mid-line to the gluteal region where the skin was removed from the back. Reflect the skin from the abdomen. D24-1 2. Locate and clean the superficial epigastric and the superficial circumflex iliac vessels (N. plates 255, 256; G. plates 2.4, 2.5). Carefully make a mid-line incision through the superficial fascia following the first skin incision. Do not cut through the linea alba. Make a second incision through the superficial fascia from the umbilicus to the crest of the ilium. While reflecting the superficial fascia laterally from the midline, look for anterior cutaneous nerves and perforating vessels piercing the anterior lamella of the rectus sheath and entering the superficial fascia (N. plate 255, 257; G. plates 2.4, 2.5). 3. Clean the external oblique m. (N. plates 249, 254 255; G. plates 2.3, 2.5, 2.6, 2.7), but do not destroy the superficial inguinal ring. Detach the external oblique muscle from its origin on the ribs and separate the muscle from the internal oblique (N. plate 254; G. plate 2.5B,2.6, 2.8, 2.9). The inguinal ligament and the superficial inguinal ring must be kept intact, so make an incision through the external oblique muscle from just above the crest of the ilium to two inches above the pubic symphysis. Do not try to separate the aponeurosis of the external oblique from the internal oblique at the linea semilunaris. Compare the direction of muscle fibers in the internal and external oblique muscles. Note the direction of the most inferior internal oblique muscle fibers compared with its superior fibers. Carefully incise the internal oblique muscle in the midaxillary line and its attachments to the costal margin and iliac crest; reflect it forward to expose the transverse abdominis muscle. Between these muscles will be the main trunks of the intercostal nerves (N. plate 257; G. plates 2.4, 2.5B). Attempt to identify the deep circumflex iliac artery. D24-2 4. Open the rectus sheath (N. plates 250, 251, 255 - 257; G. plates 2.4, 2.5); make a longitudinal incision through its exposed anterior portion, from a point just below the xiphoid process to a pint just above the pubic symphysis, parallel and just lateral to the linea alba. From the upper end of the first incision, make a transverse incision and then a second transverse incision just below the umbilicus. Now make a transverse incision in the rectus abdominis m. just below the umbilicus and reflect the muscle superiorly. Identify the superior and inferior epigastric arteries (N. plate 255; G. plate 2.5). The posterior lamella of the rectus sheath can now be seen. It consists of the aponeurosis of the transverse abdominis and the internal oblique. The posterior lamella ends below the level of the umbilicus as the arcuate line; below this level you only have transversalis fascia (N. plates 251, 255, 256; G. plate 2.59). Below the arcuate line the anterior lamella of the rectus sheath consists of the aponuerosis of all three muscles. Just above the pubic symphysis the internal oblique and the transverse abdominis fuse to form the conjoined tendon. 5. Locate the superficial inguinal ring in the external oblique aponeurosis just above the pubic tubercle (N. plates 260, 261; G. plates 2.7, 2.8). The collagen bundles forming the superior and medial boundaries of the ring are the medial crural fibers and the inferior fibers are the lateral crural fibers. Lateral to the superficial ring, youhave the intercrural fibers. Identify the spermtic cord, the round ligament and the ilioinguinal nerve, all emerge from the superficial inguinal ring. 6. Make a small incision through the linea alba below the umbilicus to reach the peritoneal cavity. Pull the abdominal wall away from the abdominal contents so as not to cut them. Extend the incision through the body wall transversely from one ASIS to the other. Inspect the deep surface of the anterior abdominal wall below the incision (N. plates 252, 253; G. plate 2.17). Extending from the apex of the bladder to the umbilicus is a peritoneal fold containing the median umbilical ligament, which is the remnant of the fetal urachus (N. plate 253; G. plate 2.17). Another peritoneal fold appears to come out of the pelvis lateral to the bladder and ascends to the umbilicus. This fold is called the median umbilical fold and it contains the medial umbilical ligament, the obliterated umbilical artery. Further lateral is another fold containing the inferior epigastric vessels. This peritoneal fold is called the lateral umbilical fold (N. plate 253; G. plate 2.17). The deep inguinal ring is just lateral to the lateral umbilical fold. Remove the peritoneum form about a two-inch radius around the deep inguinal ring and clean the structures which enter or leave the ring. In the male, these are the ductus deferens and the neurovascular bundle for the testes; in the female it is the round ligament of the uterus (N. plates 255, 259, 387; G. plate 2.8 – 2.10, 2.15). 7. Remove the skin from the anterior surface of the pubis and follow the spermatic cord down to the testes (N. plates 255, 259, 387; G. plate 2.8, 2.12, 2.15). Identify tunica albuginea, tunica vaginalis, epididymus, ductus deferens and the pampiniform venous plexus. D24-3 D24-4