Unit 08 — Female Genital System · Question Bank

Overview

The uterine tubes are two tortuous tubes, each approximately 10–12 cm long and 0.5 cm in diameter, situated on the upper margins of the broad ligaments. They transmit the ovum from the ovary to the uterus and are the normal site of fertilisation. Their abdominal orifice opens into the peritoneal cavity; their uterine orifice opens into the superior angle of the uterine cavity.

Four parts (lateral to medial)

• Infundibulum: The funnel-shaped, most lateral part. Opens into the peritoneal cavity. Bears fimbriae (finger-like projections) including the elongated ovarian fimbria attached to the ovary. Function: captures the ovum at ovulation.
• Ampulla: The longest and widest part (~5–8 cm). Thin, distensible wall. Site of normal fertilisation — sperm and ovum meet here.
• Isthmus: Approximately 2.5 cm long. Narrow, thick-walled. Site of tubal ligation (surgical sterilisation).
• Uterine (intramural) part: Approximately 1 cm, traverses the uterine wall. Opens into the uterine cavity via the uterine orifice.

Why ectopic pregnancy is most common in the ampulla

Because fertilisation normally occurs in the ampulla, if the embryo fails to migrate toward the uterus (due to ciliary dysfunction, tubal adhesions from prior PID, or endometriosis), it implants in the ampullary wall. The thin, distensible wall of the ampulla allows growth to ~8–12 weeks before rupturing, producing haemoperitoneum. Isthmic ectopics rupture earlier (narrower lumen, thicker wall).

Parts of the uterus

• Fundus: The rounded superior part above the uterine tube orifices.
• Body (corpus): The main part, flattened anteroposteriorly. Contains the triangular uterine cavity.
• Isthmus: A constricted segment ~1 cm long between body and cervix. During pregnancy it forms the lower uterine segment (site of caesarean section).
• Cervix: The lower cylindrical part, subdivided into the supravaginal part (above vaginal attachment) and the vaginal part (ectocervix, projects into vaginal vault). The cervical canal opens at the internal os (above) and external os (below). The squamocolumnar junction at the external os is the site of Pap smear sampling and cervical carcinoma origin.

Normal position

Anteverted (uterus tilted forward relative to vagina, ~90° angle) and anteflexed (body bent forward on cervix at the isthmus, ~170° angle). Maintained by its ligaments.

True supporting ligaments (prevent prolapse)

• Cardinal ligament (Mackenrodt's / transverse cervical ligament): Condensation of pelvic fascia from cervix/upper vagina to lateral pelvic wall. Prevents inferior descent (prolapse).
• Uterosacral ligament (rectouterine ligament): Runs from cervix posteriorly to the sacrum. Maintains anteflexion; prevents prolapse.

Peritoneal fold ligaments (do NOT prevent prolapse)

• Broad ligament: Double peritoneal fold from uterus to lateral pelvic wall. Contains uterine tube (mesosalpinx), ovary attachment (mesovarium), round ligament, and ovarian ligament (mesometrium). No tensile support.
• Round ligament: Fibromuscular cord from uterine cornua through inguinal canal to labia majora. Maintains anteversion but does NOT prevent prolapse.

Structure of the uterine wall

Three coats (inner to outer): Endometrium (functional layer shed at menstruation; basal layer regenerates it) → Myometrium (smooth muscle; contracts in labour and menstruation) → Serous coat / perimetrium (visceral peritoneum).

Position

The ovaries are a pair of oval gonadal organs, one on each side of the uterus, situated in the ovarian fossa (a shallow depression on the lateral pelvic wall, between the external iliac vessels anteriorly and the ureter/internal iliac vessels posteriorly). Each ovary is approximately 3 cm × 2 cm × 1 cm.

Surfaces and borders

• Surfaces: Medial (faces uterus) and lateral (faces pelvic wall).
• Borders: Anterior (mesovarian) border — attached to the mesovarium; bears the hilum where vessels enter. Posterior (free) border — faces the ureter.
• Extremities: Superior (tubal) extremity — related to the fimbriae; inferior (uterine) extremity — connected to the uterus by the ovarian ligament.

Internal structure

Outer cortex (contains numerous follicles in different stages of maturation) and inner medulla (blood vessels, lymphatics, nerves, connective tissue). One follicle matures and is discharged per menstrual cycle.

Supporting structures

• Mesovarium: Peritoneal fold connecting anterior border of ovary to the posterior layer of the broad ligament. Carries vessels to/from the hilum.
• Ovarian ligament (proper ligament of ovary): Fibromuscular cord from the inferior (uterine) extremity of the ovary to the uterine cornua. Holds ovary toward uterus.
• Suspensory ligament of ovary (infundibulopelvic ligament): Peritoneal fold from the superior (tubal) extremity of the ovary to the pelvic side wall (over the iliac vessels at the pelvic brim). Contains: ovarian artery (from abdominal aorta at L2), ovarian vein, lymphatics, autonomic nerves.

Blood supply

• Ovarian artery: Arises from the abdominal aorta at L2 (below renal arteries). Enters via the suspensory ligament, crosses the ureter at the pelvic brim, runs through the mesovarium to the hilum. Also anastomoses with the uterine artery.
• Ovarian vein: Right ovarian vein → IVC directly. Left ovarian vein → left renal vein. This asymmetry explains why left-sided varicoceles (and ovarian vein thrombosis) are more common.

Clinical significance of the suspensory ligament

The suspensory ligament must be ligated during oophorectomy. The ureter runs close to it (medially) at the pelvic brim and is at risk of inadvertent ligation or transection during surgery (“avoid the bridge”).

Extent and general

The vagina is a fibromuscular tube extending from the cervix of the uterus (above) to the vaginal vestibule (below), approximately 8–10 cm long. It serves as the birth canal, the passage for menstrual flow, and the female organ of copulation. The anterior wall is shorter than the posterior wall (because the cervix projects into the anterior aspect of the upper vagina).

Relations

• Anterior: Urethra (lower part) and base of the urinary bladder / vesicovaginal septum (upper part).
• Posterior: Perineal body (lower part), anal canal (middle), and rectouterine pouch of Douglas (upper part, above posterior fornix).
• Lateral: Pelvic floor muscles (levator ani), ureters (cross close to lateral fornices), and the cardinal ligaments.

Fornices

The upper vagina surrounds the vaginal part of the cervix, forming a circular recess called the vaginal fornix, divided into anterior, posterior, and two lateral fornices.

• Posterior fornix: Deepest; lies immediately below the rectouterine pouch (pouch of Douglas), separated from it only by the posterior vaginal wall and peritoneum.
• Anterior fornix: Shallower; related to the vesicouterine pouch above.
• Lateral fornices (×2): Related to the ureters and uterine arteries.

Clinical importance of the posterior fornix

The thin wall between the posterior fornix and the pouch of Douglas allows direct clinical access to the most dependent peritoneal recess in the erect female. Free fluid (blood, pus) collects here first in the erect position.

Culdocentesis

Culdocentesis (colpocentesis) is the procedure of inserting a needle through the posterior vaginal fornix into the rectouterine pouch to aspirate peritoneal fluid. Indications: (1) Suspected ruptured ectopic pregnancy — aspiration of non-clotting blood confirms haemoperitoneum; (2) Pelvic abscess drainage (e.g. tubo-ovarian abscess); (3) Diagnosis of ovarian cyst rupture. Now largely superseded by transvaginal ultrasound but remains relevant in resource-limited settings.

Peritoneum in the female pelvis — overview

The peritoneum dips into the female pelvis and reflects over the pelvic viscera, creating peritoneal pouches and folds. Descending from the anterior abdominal wall, it covers the superior surface of the bladder, then reflects onto the anterior surface of the uterus (vesicouterine pouch), covers the fundus and body, descends the posterior uterine surface to the posterior vaginal fornix, and then reflects onto the rectum (rectouterine pouch), eventually becoming the sigmoid mesocolon.

Formation of the broad ligament

The peritoneum passes laterally from the uterus to the lateral pelvic walls, creating a double-layered peritoneal fold called the broad ligament. It contains the uterine tube (in the mesosalpinx), the ovary (attached via the mesovarium), and the round ligament and ovarian ligament (in the mesometrium).

Peritoneal pouches

• Vesicouterine pouch: Between the bladder (posteriorly) and the uterus (anteriorly), at the level of the junction of body and cervix. It is relatively shallow. Clinical: caesarean section peritoneum (vesicouterine peritoneum) is incised and reflected to access the lower uterine segment. Fluid here is palpable on pelvic examination as anterior vaginal wall fullness.
• Rectouterine pouch (pouch of Douglas): Between the posterior surface of the uterus/posterior vaginal fornix and the anterior surface of the rectum. It is the lowest point of the peritoneal cavity in the erect female. Bounded laterally by the uterosacral ligaments (rectouterine folds).

Clinical significance of the pouch of Douglas

• Collection of free fluid: Blood (ruptured ectopic, ruptured ovarian cyst, pelvic trauma), pus (pelvic inflammatory disease, appendicitis, diverticulitis), ascitic fluid, ovarian cancer deposits — all collect here first in the erect position.
• Culdocentesis: Needle aspiration through the posterior vaginal fornix to diagnose haemoperitoneum (ruptured ectopic pregnancy) or drain a pelvic abscess.
• Pouch of Douglas obliteration: Endometriosis involving the uterosacral ligaments and posterior vaginal wall can obliterate this pouch, causing fixed retroversion, deep dyspareunia, and dyschezia.
• Peritoneal metastases: Ovarian and colorectal cancer seed this pouch (Blumer's shelf on rectal examination).
• Drainage of pelvic abscess: Abscess can be drained through posterior colpotomy (incision through posterior fornix).