Henry Gray (18251861). Anatomy of the Human Body. 1918. the
Obturator internus and are enclosed in a special canalAlcocks
canalformed by the obturator fascia. The fascia of the
Piriformis is very thin and is attached to the front of the
sacrum and the sides of the greater sciatic foramen; it is
prolonged on the muscle into the gluteal region. At its sacral
attachment around the margins of the anterior sacral foramina it
comes into intimate association with and ensheathes the nerves
emerging from these foramina. Hence the sacral nerves are
frequently described as lying behind the fascia. The internal
iliac vessels and their branches, on the other hand, lie in the
subperitoneal tissue in front of the fascia, and the branches to
the gluteal region emerge in special sheaths of this tissue,
above and below the Piriformis muscle. FIG. 402 Coronal section
of pelvis, showing arrangement of fasciæ. Viewed from behind.
(Diagrammatic.) (See enlarged image) The diaphragmatic part of
the pelvic fascia(Fig. 402) covers bot