Part 1: Opening the Pelvic Cavity

In the MALE specimens, reflect the penis and scrotum over to the right side.

Expose the pelvic symphysis on the ventral midline by removing part(s) of the adductor m. surrounding the midline. Use the pruners/snips provided in the lab to cut through the pelvic symphysis (ventral midline of the pelvis).

• Dissection Note: It is easiest to approach the midline of the pelvis from the hind limb that was previously dissected in Chapter 2. Note that you must cut through/cut out part of the adductor muscle to get to the ventral midline.

On the hind limb that was previously dissected in Chapter 2, palpate/locate the wing of the ilium and sever all muscles attaching to its medial and ventral surfaces. (Use a sharp scalpel to ‘outline’ the wing of the ilium by cutting through all of the muscles attached to the bone.)

Move the hind end of the specimen to the edge of the dissection table. Position the animal so that the dorsal midline is on the table edge and the hind limb extends over the edge. Apply ample force and downward pressure to the half of the pelvis you outlined in the previous step, while abducting the hind limb to crack the pelvis open. (Try to avoid popping the head of the femur out of the acetabulum; this will make it harder to open the pelvis.) Leave the hind limb attached to the body. (See DG pg. 182)

• Note that in males you may need to cut through the attachment point of the penis to the ischium (this is the ‘crus’ of the penis which will be covered later in this lab) in order to successfully crack open the pelvis.

After opening the pelvis, identify the obturator n. (a nerve that arises from the lumbosacral plexus) on the medial side of the ilium passing deep to the levator ani m. and out of the pelvis through the obturator foramen; if possible trace it as it emerges ventrally from the obturator foramen and enters the adductor m. (See DG Figs. 4-58, 4-65, 4-66, and 4-67)