Female Pelvic Organs

Parts:

• Fundus: The rounded superior portion, above the level of the uterine tube openings.
• Body: The main portion, between the fundus and isthmus, where the uterine cavity is widest.
• Isthmus: A slight narrowing between the body and cervix (corresponds to the lower uterine segment of obstetric terminology).
• Cervix: The lower, more fibrous portion, projecting into the upper vagina; further divided into the supravaginal part (above the vaginal attachment) and the vaginal part (portio vaginalis), which protrudes into the vaginal vault, surrounded by the vaginal fornices.

Normal position:

• Anteversion: The angle between the cervix's long axis and the vagina's long axis, normally the uterus is tilted forward (anteverted) relative to the vaginal axis, roughly 90° or slightly more.
• Anteflexion: The angle between the body's long axis and the cervix's long axis, normally the body is also flexed forward relative to the cervix, roughly 170°, creating the overall "tipped forward and folded" normal resting position.
• Together, anteversion and anteflexion describe the uterus's typical resting orientation, lying roughly horizontally over the bladder in a woman in the standing position; variations (retroversion, retroflexion, a tilted-backward uterus) are common normal anatomical variants in a substantial minority of women, generally of minimal clinical significance unless symptomatic or complicating specific procedures.

Relations:

• Anterior: Vesicouterine pouch, superior surface of the bladder.
• Posterior: Rectouterine pouch (pouch of Douglas), rectum.
• Lateral: Broad ligament (with the uterine tubes, round ligament, ovarian ligament, and uterine vessels within it), and (at the level of the cervix) the ureter, running close to the lateral cervix within the base of the broad ligament (see uterine artery relationship below).

• The uterus is supported by a combination of the pelvic floor (levator ani, providing the primary passive muscular platform), and several fascial condensations (endopelvic fascia thickenings around the uterine vessels, rather than discrete independent ligaments, though named and functionally treated as such):

Transverse cervical (cardinal) ligaments:

• The most important lateral support, extending from the cervix/lateral vaginal fornix to the pelvic side wall, containing the uterine vessels within their substance, provide the primary mechanical support preventing uterine descent/prolapse, more so than any other single ligamentous structure.

Uterosacral ligaments:

• Extend posteriorly from the cervix/upper vagina to the sacrum (passing on either side of the rectum), providing posterior support and helping maintain the uterus's anteverted position by resisting posterior displacement.

Pubocervical ligaments:

• Extend anteriorly from the cervix to the pubic bones (passing around the bladder neck), providing anterior support.

Round ligament of the uterus:

• Extends from the uterine cornu (near the uterine tube origin), through the broad ligament, then through the inguinal canal (see Abdomen content) to terminate in the connective tissue of the labium majus, the embryological homologue of the gubernaculum testis.
• Provides relatively minor structural support compared to the fascial condensations above (a common point of confusion/misconception, the round ligament does NOT primarily support the uterus against prolapse), but does contribute to maintaining the uterus's anteverted orientation by its forward pull.

Uterine artery:

• The primary arterial supply, a branch of the internal iliac artery's anterior division, running within the base of the broad ligament (transverse cervical ligament region) to reach the lateral cervix, then ascending along the lateral uterine border (within the broad ligament) toward the fundus, where it anastomoses with the ovarian artery.
• Relationship to the ureter: Crosses anterior to and superior to the ureter, approximately 2 cm lateral to the cervix, the classic "water under the bridge" relationship (uterine artery = bridge; ureter = water flowing beneath), the single most clinically important pelvic anatomical relationship for gynaecological surgery, given the substantial risk of inadvertent ureteric injury/ligation during hysterectomy if the uterine artery is clamped without first clearly identifying and protecting the ureter at this crossing point.

Ovarian artery:

• Arises directly from the abdominal aorta (at approximately L2, alongside the testicular artery's equivalent origin; see Abdomen content), descending within the suspensory ligament of the ovary (infundibulopelvic ligament) to reach the ovary, and anastomosing with the uterine artery near the uterine fundus/uterine tube, providing collateral supply to the uterus and tube, and the sole direct blood supply to the ovary itself.

• Paired tubes extending laterally from the uterine cornua toward the ovaries, lying within the free superior border of the broad ligament (mesosalpinx), divided into four parts:

Intramural (interstitial) part:

• The short segment traversing the uterine wall itself, the narrowest part of the tube.

Isthmus:

• The narrow, thick-walled segment immediately lateral to the uterine cornu, continuous with the intramural part, the most common site of tubal ligation for sterilisation, and a relatively common site of ectopic pregnancy implantation given its narrow lumen.

Ampulla:

• The longest, widest, and most tortuous part, where fertilisation normally occurs: also the single most common overall site of ectopic (tubal) pregnancy, given both its length (providing the most total surface area/opportunity for an embryo to implant before reaching the uterine cavity) and its relatively wide but still non-uterine lumen.

Infundibulum:

• The funnel-shaped, most lateral part, opening into the peritoneal cavity near the ovary.

Fimbriae:

• Finger-like projections from the infundibulum's margin, partially draping over the ovary (the ovarian fimbria being the longest, typically attached to or closely applied to the ovary itself), helping to capture the released oocyte at ovulation and guide it into the tube, the anatomical basis for the peritoneal cavity's functional (though not literal) continuity with the external environment via the tubes, uterus, and vagina in females.

Position:

• Paired, almond-shaped gonads lying on the lateral pelvic wall, typically within a shallow peritoneal depression termed the ovarian fossa (bounded by the external iliac vessels and the ureter/internal iliac vessels), though position is variable, particularly after childbirth (which can alter pelvic ligament tension and organ position).

Ligaments:

• Mesovarium: The short peritoneal fold (part of the broad ligament) attaching the ovary's hilum to the posterior broad ligament, transmitting the ovarian vessels/nerves, the ovary's surface itself is not covered by peritoneum, a unique feature among pelvic organs.
• Ovarian ligament (ligament of the ovary): Extends from the ovary to the uterine cornu (just below the uterine tube's origin), lying within the broad ligament, the embryological homologue of the round ligament of the uterus (both derived from the gubernaculum), together forming a continuous ligamentous line from the ovary to the labium majus, interrupted only by the uterus itself.
• Suspensory ligament of the ovary (infundibulopelvic ligament): Extends from the ovary superolaterally to the pelvic side wall/posterior abdominal wall, containing the ovarian vessels (artery and vein) and nerves, NOT part of the broad ligament proper (a separate peritoneal fold), and the key structure to identify and preserve/ligate carefully during oophorectomy, given its neurovascular contents and its close proximity to the ureter, which runs just deep/medial to it as the ureter crosses the pelvic brim, a second major ureteric injury risk point in female pelvic surgery, alongside the uterine artery crossing.

Blood supply:

• Ovarian artery (from the aorta, via the suspensory ligament), the primary supply.
• Venous drainage: Asymmetric, mirroring the testicular vein pattern, right ovarian vein drains directly into the IVC; left ovarian vein drains into the left renal vein.

Lymphatics:

• Drain to the para-aortic (lumbar) nodes, following the ovarian vessels back to their aortic/caval origin, reflecting the ovary's high embryological origin, exactly mirroring the testis's lymphatic drainage pattern (para-aortic, not inguinal) despite the very different final adult position of the two gonads.

Walls:

• A fibromuscular tube extending from the cervix to the vestibule, with anterior and posterior walls that are normally in apposition (a potential rather than actual open space, except when distended, e.g., during intercourse, examination, or childbirth); the posterior wall is notably longer than the anterior wall, given the oblique angle at which the cervix projects into the vaginal vault.

Fornices:

• The recesses formed around the cervix where it projects into the vaginal vault, anterior, posterior, and two lateral fornices; the posterior fornix is the deepest and clinically most significant, lying in direct contact with the rectouterine pouch (Douglas's pouch) peritoneum, separated only by the thin posterior vaginal wall, the basis for culdocentesis (posterior fornix needle aspiration) and for the clinical assessment of pouch of Douglas fluid collections via bimanual/speculum examination.

Relations:

• Anterior: Bladder base and urethra (the urethra embedded within the anterior vaginal wall in its lower part).
• Posterior: Rectouterine pouch (upper third, via the posterior fornix), rectum (middle third, directly related), perineal body/anal canal (lower third).
• Lateral: Levator ani, ureter (upper part, as it passes close to the lateral vaginal fornix en route to the bladder, a third notable ureteric proximity point in the female pelvis, alongside the uterine artery and infundibulopelvic ligament relationships).

Blood supply:

• Vaginal artery (branch of the internal iliac artery, or sometimes arising as a branch of the uterine artery), the primary supply, supplemented by vaginal branches of the uterine artery (upper vagina), middle rectal artery, and internal pudendal artery (lower vagina), a rich longitudinal anastomotic network spanning the vagina's full length, similar in principle to the rectum's multi-source supply.

Lymphatics:

• Upper two-thirds: Drain to the internal and external iliac nodes (following the vaginal/uterine vessels, an internal, "pelvic" drainage pattern).
• Lower third: Drains to the superficial inguinal nodes (an external, "perineal" drainage pattern, given this part's shared embryological/anatomical origin with the vulva), this dual drainage pattern (upper pelvic, lower inguinal) mirrors the equivalent transition seen in the anal canal at the pectinate line, and is clinically relevant to the differing lymphatic spread patterns of vaginal cancer depending on the level of the primary tumour.

Innervation:

• Upper vagina: autonomic (inferior hypogastric plexus, largely insensate to touch, consistent with its visceral/embryological origin above the "pelvic pain line" region); lower vagina, somatic (pudendal nerve, sensate, given its perineal/ectodermal-adjacent origin), again mirroring the analogous transition at the pectinate line in the anal canal.

Ectopic pregnancy:

• Implantation of a fertilised ovum outside the uterine cavity, most commonly within the uterine tube (tubal ectopic pregnancy: the ampulla is the single most common site, followed by the isthmus); can also (rarely) occur in the ovary, cervix, or abdominal cavity.
• Risk is increased by any factor impairing normal tubal transport (prior pelvic inflammatory disease/tubal scarring, prior tubal surgery, previous ectopic pregnancy), the underlying anatomical principle being impaired or delayed transit of the fertilised ovum through the tube toward the uterine cavity.
• Rupture (most dangerous with isthmic implantation, given the isthmus's narrower, less distensible lumen and closer proximity to major vessels) causes intraperitoneal haemorrhage, classically presenting with pain and blood collecting in the rectouterine pouch, detectable clinically or by ultrasound/culdocentesis.

Hysterectomy anatomy:

• Requires careful identification and ligation of the uterine artery (with prior awareness of the underlying ureter, given the "water under the bridge" crossing relationship, the single most critical step in avoiding ureteric injury), division of the transverse cervical (cardinal) and uterosacral ligaments (the main structural supports requiring surgical division to mobilise/remove the uterus), and careful dissection of the vesicouterine and rectouterine peritoneal folds anteriorly and posteriorly.
• Additional care is needed near the infundibulopelvic ligament if oophorectomy is performed concurrently, given the ureter's proximity there as well.

Ureteric injury:

• The two classic sites of ureteric injury risk in female pelvic/gynaecological surgery are: (1) the uterine artery crossing ("water under the bridge," near the lateral cervix), and (2) the infundibulopelvic ligament (suspensory ligament of the ovary, during oophorectomy), both requiring deliberate identification and protection of the ureter before ligating the adjacent vascular pedicle.

Uterine prolapse:

• Descent of the uterus (and, in more advanced cases, the cervix and even the entire uterus through the vaginal introitus) resulting from weakness/damage to its supporting structures, primarily the levator ani (muscular support) and the transverse cervical/uterosacral ligaments (fascial support), most commonly following obstetric trauma (vaginal delivery, particularly prolonged or instrumental), but also related to ageing, menopausal oestrogen decline, and chronic raised intra-abdominal pressure (obesity, chronic cough).
• Graded by severity (from mild descent to complete procidentia, where the uterus protrudes entirely outside the vaginal introitus), and often accompanied by concurrent anterior (cystocele) and/or posterior (rectocele) vaginal wall prolapse, given the shared underlying pelvic floor weakness.