ABSTRACT
The pudendal nerve is the one of the longest nerves of the pudendal plexus. This plexus is also known as the sacral plexus. It originates predominantly from the ventral branches of the second, third, and fourth sacral nerve; but also receives tributaries of other ventral branches of the sacral nerves as well as sympathetic and parasympathetic fibers. The plexus is situated in front of the coccygeus muscle and the inferior margin of the piriformis muscle. The sacral artery and sacral veins run in front of the nerve. The plexus gives off small branches, nervi pelvici. These branches contain sympathetic and parasympathetic fibers that innervate the rectum, the inferior bladder, the urethra and the genital organs. The pudendal nerve leaves the pelvis through the foramen infrapiriforme, the distal portion of the greater sciatic foramen. It makes a loop around the spine of the ischium, behind the internal pudendal artery and reenters the pelvis together with the artery through the foramen ischiadicum minus (the lesser sciatic foramen) to reach the lateral wall of the ischiorectal fossa. In the frontal section, the ischiorectal fossa has the shape of a triangle, with the base caudal and the apex pointing cranially (Figure 35.1). The lateral limit of the fossa is the internal surface of the ischium covered by the obturator internus muscle, its fascia, the medial aspect of the levator ani muscle and its fascia. The base of the fossa is formed by subcutaneous fat covered by fascia lunata and skin. The apex corresponds to the line joining the obturator internus muscle and the levator ani muscle.
