Pelvic Fascia and Peritoneum

Lines the internal surface of the pelvic walls and the superior (pelvic) surface of the pelvic diaphragm (levator ani/coccygeus), continuous with the transversalis fascia of the abdomen superiorly (an important continuity, since infection or fluid within one fascial plane can potentially track into the other).

• Includes the obturator fascia (over obturator internus) and the superior fascia of the pelvic diaphragm.

• A looser, more variable connective tissue layer investing the pelvic organs themselves, condensing in places to form recognisable fascial sheaths and ligamentous structures around individual organs (e.g., the fascial sheath of the rectum, the pubocervical and rectovaginal fascia).
• Continuous with the parietal pelvic fascia where organs pierce through or lie adjacent to the pelvic walls/floor.

• A collective term for the connective tissue matrix filling the extraperitoneal pelvic space, encompassing both the visceral fascia immediately around each organ and the looser areolar tissue and neurovascular sheaths connecting them, essentially the "packing" and support structure of the entire subperitoneal pelvis.
• Provides passage and protection for vessels, nerves, lymphatics, and ureters as they course between the pelvic wall and the viscera, and contributes the fascial ligamentous condensations.

• Localised thickenings of the endopelvic fascia around blood vessels and nerve bundles, functioning as suspensory/supportive ligaments for the pelvic organs even though they are not discrete, independent structures in the way a limb ligament is, rather, they represent regions where the fascia is denser due to the vessels/nerves it surrounds.
• Named examples include the transverse cervical (cardinal) ligament, uterosacral ligament, and pubocervical ligament (female-specific, full detail in Section 9), and equivalent condensations around the rectum (lateral rectal ligaments, containing the middle rectal vessels) and bladder (pubovesical/puboprostatic ligaments).

• These are best understood as fascial condensations around neurovascular pedicles, rather than true discrete ligaments, though they are named and function similarly to ligaments in providing organ support and are treated as surgical landmarks accordingly.

The pelvic peritoneum drapes over the superior surfaces of the pelvic organs, creating characteristic pouches whose pattern differs by sex.

Male

Rectovesical pouch:

• The peritoneal reflection between the posterior surface of the bladder and the anterior surface of the rectum, the most dependent part of the male peritoneal cavity in the upright position, and therefore the site where free intraperitoneal fluid (blood, pus, ascites) characteristically collects.
• Bounded laterally by the rectovesical (sacrogenital) folds, peritoneal ridges overlying the underlying ligamentous condensations.

Female

Vesicouterine pouch:

• Between the posterior surface of the bladder and the anterior surface of the uterus (at the level of the isthmus), relatively shallow, of lesser clinical significance than the rectouterine pouch, given the uterus's typical anteverted/anteflexed position bringing the bladder and uterine body into close apposition here.

Rectouterine pouch (pouch of Douglas):

• Between the posterior surface of the uterus/upper vagina and the anterior surface of the rectum, the most dependent part of the female peritoneal cavity in the upright position.
• Classic site for fluid collection (blood: ruptured ectopic pregnancy; pus, pelvic inflammatory disease/abscess; ascites, malignancy) assessed clinically via posterior vaginal fornix examination, and accessible for culdocentesis (needle aspiration through the posterior vaginal fornix), a historically important diagnostic procedure, now largely superseded by ultrasound but still conceptually and anatomically relevant.
• A common site for endometriotic deposits (given gravity-dependent pooling of retrograde menstrual flow, one proposed mechanism of endometriosis) and for early transperitoneal spread of ovarian malignancy.

• A double layer of peritoneum draping over the uterus, uterine tubes, and their associated vessels/ligaments, extending laterally from the uterus to the pelvic side walls, not a true suspensory ligament providing significant structural support (despite its name), but rather a peritoneal fold/mesentery.
• Contains, between its two layers: the uterine tubes (superior free edge), the round ligament of the uterus (anteriorly), the ovarian ligament (posteriorly), the uterine and ovarian vessels, the ureter (in its lower part, close to the uterine artery for the critical "water under the bridge" relationship), and loose connective tissue/fat.
• Subdivided into three named parts based on which structure each part's peritoneal fold specifically invests:

Mesometrium:

• The largest part of the broad ligament, the portion draping over and supporting the body of the uterus itself, extending down to the pelvic floor and lateral pelvic wall, the main "bulk" of the broad ligament.

Mesosalpinx:

• The portion of the broad ligament superior to the mesovarium, draping over and supporting the uterine tube, containing the tubal branches of the uterine and ovarian vessels; occasionally contains embryological remnants (e.g., the epoophoron, paroophoron, vestigial mesonephric duct/tubule structures, of minor clinical significance except as a rare cystic lesion origin).

Mesovarium:

• A short posterior fold of the broad ligament attaching to the ovary's hilum, transmitting the ovarian vessels and nerves to/from the ovary, notably, the ovary itself is not covered by peritoneum at its surface (unlike almost every other intraperitoneal organ), since the mesovarium attaches at the hilum only, leaving the ovarian surface directly exposed to the peritoneal cavity, this unique lack of a peritoneal covering is relevant to the ease of direct transperitoneal spread of ovarian surface pathology (e.g., ovarian malignancy) compared to organs with a complete serosal covering.

• The subperitoneal (extraperitoneal) pelvic space lies between the peritoneum above and the pelvic floor below, containing the bulk of the pelvic organs (bladder, most of the rectum, and the lower reproductive organs), along with the endopelvic fascia, vessels, nerves, ureters, and lymphatics described throughout this section.
• Named potential spaces within this compartment (relevant to surgical dissection planes) include the retropubic (prevesical/Retzius) space: between the pubic symphysis/bladder anteriorly and the anterior abdominal wall, a key surgical access space for retropubic prostatectomy or bladder neck procedures, and the presacral space, between the rectum and the sacrum, an important dissection plane in rectal cancer surgery (total mesorectal excision).

• The endopelvic fascia is organised into recognisable, surgically important planes/spaces around each organ (vesicovaginal, rectovaginal, pararectal, paravesical spaces, among others in more detailed surgical anatomy teaching), these represent relatively avascular planes that surgeons deliberately develop to mobilise organs (e.g., during hysterectomy or rectal resection) while preserving the neurovascular bundles that run within the surrounding fascial condensations.
• Awareness of these planes and their relationship to the named ligamentous condensations (transverse cervical, uterosacral, lateral rectal ligaments) is central to nerve-sparing and vessel-preserving pelvic surgical technique.