Now we’ll move on to look at the blood vessels and then the nerves of the pelvis and perineum. First, the blood vessels.
Here’s the pelvic cavity, seen from above, with the abdominal and pelvic organs removed, and the soft tissue lining of the cavity intact. The pelvic cavity is lined, somewhat irregularly, with peritoneum. Beneath that, there’s a layer of pelvic fascia that’s continuous with the endo-abdominal fascia.
The internal iliac artery, which we saw in the last section, is hidden, just under here. To see the pelvic blood vessels, we’ll remove one half of the pelvis and go round to a medial view. We’ll also remove the lining of peritoneum and pelvic fascia. In this dissection the veins, which follow the arteries closely, have been removed to simplify the picture.
The arteries of the pelvic region are all branches of the internal iliac artery. The way they arise is quite variable. This is the superior gluteal artery, this is the inferior gluteal. They pass through the greater sciatic foramen to supply the buttock region.
This is the internal pudendal artery, which we’ll return to in a minute. This is the obturator artery, passing forwards into the obturator canal, along with the obturator nerve. The most anterior branch of the internal iliac comes to a blind end; in the fetus it’s the umbilical artery.
Branches to the pelvic organs arise in a widely varying fashion. These are the divided ends of the vesical arteries, superior and inferior, which supply the bladder. This is the middle rectal artery, which supplies the lower part of the rectum.
In the female, the uterine arteries also arise, directly or indirectly, from the internal ilac. The branch of the internal iliac that concerns us most closely here is the internal pudendal artery
It supplies the blood supply to the perineum. To reach the perineum, the internal pudendal artery goes out through the greater sciatic foramen, around the sacrospinous ligament, and back in through the lesser sciatic foramen In this way, the pudendal artery ends up below the pelvic diaphragm. To follow its course we’ll go round to the back. The gluteal vessels and the sciatic nerve have been removed.
Here’s the internal pudendal artery, emerging below piriformis. It passes behind the sacro-spinous ligament, which is here, and behind this small muscle, the superior gemellus
The internal pudendal artery runs downwards and forwards, along the medial aspect of obturator internus. Its branches supply the anal sphincter, the pelvic diaphragm, the external genital structures in the female, and the penis in the male.