Prelab Images - Pelvic Neurovasculature

Prelab should consist of reading the lab manual and dissector answers and viewing the dissection video. To begin your study, you may find it useful to look over the Netter's or LWW Atlas images listed below.

Step 1. Examine the bony pelvis. (Play movie)

Plate N486 or TG3-05 and TG3-04 identifies the obturator foramen and groove. Plates N486 or TG3-04 and TG3-05 and N248 or TG6-03 show the greater and lesser sciatic notches and the spine of the ischium. Plate N486 or TG3-05 and TG3-04 labels the ischial tuberosity. Plates N248 or TG6-06A and N352 or TG6-06B show the sacroiliac joint. Plates N352 or TG6-06 and N503 or TG3-07 review how the sacrotuberous and sacrospinous ligaments help to form the greater and lesser sciatic foramina.

Step 2. Clean and identify the branches of the internal iliac artery, removing the corresponding veins. (Play movie)

Plate N364 or TG6-17A and TG6-17B shows the internal iliac artery lying lateral to the pelvic viscera. To trace this artery you will need to pull the pelvic viscera medially. Plates N400 and N401 or TG6-09A and TG6-09B review the course of the ureter in the male and the female. Plates N402 or TG6-17 and N403 or TG6-17 show the common iliac artery and vein branching into internal and external iliac vessels. Plates N402 or TG6-17A and N403 or TG6-17B show the external iliac vessels moving toward the inguinal ligament (the ligament is unlabelled). Plate N253 or TG5-07 shows the external iliac artery giving off the inferior epigastric artery before passing under the inguinal ligament. Plate N255 or TG5-05 shows this artery coursing superiorly to eventually anastomose with the superior epigastric artery (branch of the internal thoracic artery). Returning to plates N402 or TG6-17A and N403 or TG6-17B you can see the internal iliac artery dividing into anterior and posterior divisions. The posterior division gives off the iliolumbar artery and the lateral sacral artery (see plate N264 or TG6-17A for the course of these arteries). The posterior division also gives off the superior gluteal artery, which passes out over the piriformis muscle out of the pelvis and into the gluteal region (N502 or TG6-22). Plates N402 or TG6-17A and N403 or TG6-17B also show the anterior division of the internal iliac artery as it terminates into inferior gluteal and internal pudendal arteries. The course of the inferior gluteal artery can be seen in plate N502 or TG3-27. The internal pudendal artery travels near the pudendal nerve in plate N503 or TG3-28 and can be seen in the perineum in plates N404 or TG6-29A and N405 or TG6-29B. Returning to plates N402 or TG6-17A and N403 or TG6-17B the first branch of the anterior division of the internal iliac artery should be the umbilical artery and not the obturator artery (although the umbilical and obturator arteries in plates N402 or TG6-17A and N403 or TG6-17B are shown going to their correct location, the umbilical artery branches off the internal iliac artery superior to the point where the obturator artery branches off). Plates N402 or TG6-17A and N403 or TG6-17B show the patent part of the umbilical artery giving off superior vesical branches before continuing on as the medial umbilical ligament (plates N363 or TG6-07 and N253 or TG5-07). Plates N402 or TG6-17 and N403 or TG6-17 show the uterine artery (female only), middle rectal artery, and the obturator artery coming off the anterior division of the internal iliac artery. Plate N487 or TG3-55 shows the obturator artery helping to supply the hip joint. An aberrant obturator artery would be found branching off of the inferior epigastric artery in plate N264 or TG5-08D (or even the external iliac artery) and running with the obturator nerve (plate N267 or TG5-09D). Plate N403 or TG6-17A or TG6-17B organizes the blood supply to the base of the bladder, prostate, and seminal vesicles (from the inferior vesicular artery). Although they are not mentioned in the dissection procedure you should be able to find vaginal and inferior vesicular arteries (N402 or TG6-17). It may also be helpful to review the blood supply to the rectum, uterus, and vagina (N398 and N404 or TG5-07).

Step 3. Identify the nerves of the pelvis. Identify the muscles of the pelvic wall and floor. (Play movie)

Plates N499 or TG3-25A and N499 or TG3-25B show a schema of the sacral plexus. The anterior sacral foramina are shown in plate N150 or TG6-04. The lumbosacral trunk (L4 and L5 combined together) and the first four sacral nerves are shown in plate N410 or TG6-18A (also see plate N499 or TG6-18B). Plate N402 or TG6-17 shows the superior gluteal artery passing between S1 and the lumbosacral trunk, although this may vary. Plates N497 or TG3-25A and N499 or TG3-25B organize the lumbosacral plexus. Plates N409 or TG6-19A and N410 or TG6-19B show the superior hypogastric plexus dividing into hypogastric nerves, which continue into the inferior hypogastric plexus. Plates N410 or TG6-18A and N412 or TG6-18B show the sympathetic trunk and sympathetic ganglia entering the pelvis medial to the anterior sacral foramina. The gray rami communicantes are labeled in plate N410 or TG6-19 (they go from sympathetic chain ganglia to the sacral spinal nerve and contain sympathetic fibers). Sacral splanchnic nerves are shown in plate N412 or TG6-18 (they contain sympathetic fibers and they go from the sympathetic chain ganglia to the inferior hypogastric plexus). Pelvic splanchnic nerves are labeled in plates N410 or TG6-19A and N412 or TG6-19B (they carry parasympathetic fibers and go from the spinal nerve to the inferior hypogastric plexus). Plate N410 or TG6-19 labels a nerve from the inferior hypogastric plexus passing superiorly to innervate the sigmoid and descending colon. Now review plates N410 or TG6-19A and N412 or TG6-19B and consider the nerve distribution to the rectum, vagina, uterus, bladder, and prostate. Plates N415, N416, and N417 or TG6-19A or TG6-19B organize the autonomic supply of the pelvic viscera.

Plates N367 or TG6-21A and N369 or TG6-21B identify the obturator internus muscle and the arcus tendineus levator ani (labeled as tendinous arch of levator ani in Netter's atlas). Plates N368 or TG6-23A, N370 or TG6-23B, and N503 or TG3-26 show the obturator internus moving from its origin (on the internal side of the obturator foramen) to its insertion (on the femur). Plates N367 or TG6-21A and N369 or TG6-21B show the pelvic diaphragm. Plate N369 or TG6-22 labels the levator ani muscle and its parts (puborectalis, pubococcygeus, and iliococcygeus). Plates N367 or TG6-21A and N369 or TG6-21B label the (ischio) coccygeus muscle. The puborectalis muscle is shown creating a bend in the rectum (marking the transition of rectum to anus) in the bottom pictures of plates N367 or TG6-15A and N368 or TG6-15B. The urogenital hiatus is shown in plates N367, N368, N369 or TG6-21A and TG6-21B, and N370 or TG6-23A and TG6-23B as an opening in the pelvic diaphragm just anterior to the rectum. The urogenital hiatus transmits the urethra in both sexes and the vagina in the female. Plates N367 or TG6-22 and N369 or TG6-21 label the piriformis muscle. The relation of this muscle to the sacral nerves and sacral plexus is shown in plates N410 or TG6-22 and N503 or TG3-28. The relationship of the piriformis muscle to the superior and inferior gluteal arteries is shown in plates N402 or TG6-22B, N403 or TG6-22D, N502 or TG3-27, and N499.