Female Pelvic Anatomy & Neurovascular Supply – Comprehensive Study Notes

Gross Overview of the Female Reproductive Tract

The lecture opens with a mid–sagittal view of the female pelvis, stressing that some organs are entirely intrapelvic while others are externally visible. The sequential path from the external genitalia to the intra-abdominal cavity is: vulva → vagina → cervix → uterus → uterine (Fallopian) tube → peritoneal cavity. Each segment is anatomically distinct yet functionally continuous, allowing menstruation, fertilisation and, unfortunately, the ascent of pathogens that may precipitate pelvic inflammatory disease.

Uterus: Situation, Segments and Angles

The uterus lies between bladder (anterior) and rectum (posterior), its peritoneal covering folding over both neighbours and thereby creating two clinically important cul-de-sacs: the vesico-uterine pouch anteriorly and the recto-uterine pouch (of Douglas) posteriorly.

Anatomical subdivisions
• Fundus: dome superior to uterine tube entry.
• Body: main muscular mass; houses the triangular uterine cavity.
• Isthmus: narrow, internal constriction between body and cervix.
• Cervix: comprises a supravaginal portion (above the vaginal fornices) and a vaginal portion that protrudes into the vagina.

Physiological orientation
• Angle of anteversion – between axis of cervix and axis of vagina – approximately 90^{\circ}; keeps uterus tilted over bladder.
• Angle of anteflexion – between axis of body and axis of cervix – approximately 170^{\circ}; prevents prolapse and optimises drainage.

Both angles depend on intact pelvic floor musculature and supportive ligaments; disruption can yield uterine prolapse.

Cervix and the Transformation Zone

The cervical canal is lined by simple columnar epithelium; the ectocervix (portion seen by speculum) is covered by stratified squamous epithelium. Their junction – the transformation (or transition) zone – undergoes constant metaplasia and is the commonest site for cervical carcinoma. Hence, Papanicolaou (Pap) smears target this region for cytological screening.

Key apertures
• Internal os: communicates canal with uterine cavity.
• External os: opens into vagina.

Uterine (Fallopian) Tubes

Each tube spans four named parts, in a lateral–to-medial sequence:

  1. Infundibulum with fimbriae – freely opens into peritoneal cavity, allowing oocyte capture but also potential spread of infection.
  2. Ampulla – widest segment; typical site of fertilisation.
  3. Isthmus – narrow, thick-walled; common for surgical sterilisation.
  4. Intramural (interstitial) part – traverses uterine wall.

Pathological relevance: salpingitis may ascend to the peritoneal cavity, generating pelvic inflammatory disease and adhesions that compromise fertility.

Ovaries and Their Ligaments

The ovary is suspended by two peritoneal folds contained within the broad ligament:
• Mesovarium – a short mesentery anchoring the ovary to the posterior layer of the broad ligament.
• Suspensory (infundibulo-pelvic) ligament – conveys ovarian vessels from lateral pelvic wall.

Additional attachments
• Ovarian ligament – fibromuscular cord linking ovary to uterine fundus.
• Round ligament of uterus – passes anteriorly, traverses the inguinal canal and terminates in the labium majus, a remnant of the fetal processus vaginalis; it helps maintain uterine anteversion.

Broad Ligament and Peritoneal Reflections

The broad ligament is a double layer of peritoneum draped from the lateral uterine border to the pelvic wall, subdivided into:
• Mesosalpinx – superior, envelops uterine tube.
• Mesovarium – posterior, suspends ovary.
• Mesometrium – largest, adjacent to uterine body.

These folds create potential spaces where fluid, pus or blood can accumulate, notably the pouch of Douglas – the most dependent point in the female peritoneal cavity when upright.

Fasciae, Perineum and Pelvic Floor Support

Superficial abdominal fascia continue into the perineum:
• Camper’s fascia – a fatty layer; forms the mons pubis and labia majora.
• Scarpa’s fascia – membranous layer; blends into Colles’ fascia (superficial perineal fascia) that invests muscles of the superficial perineal pouch.

Muscular supports
• Levator ani (pubococcygeus, puborectalis, iliococcygeus) and coccygeus constitute the pelvic diaphragm, crucial for visceral support.
• Superficial perineal muscles – bulbospongiosus, ischiocavernosus, superficial transverse perineal – overlay erectile tissues such as the clitoris.
• Perineal body – central fibromuscular node; tearing during childbirth predisposes to prolapse.

Neurovascular Supply and Autonomic Control

Sympathetic
• Preganglionic fibres originate from T12 to L2; travel via lumbar splanchnic nerves → intermesenteric plexus → superior hypogastric plexus → right & left hypogastric nerves → inferior hypogastric (pelvic) plexus.
• Function: vasomotor tone, uterine contraction during menstruation and (in males) emission.

Parasympathetic
• Pelvic splanchnic nerves S2–S4 join the inferior hypogastric plexus.
• Function: vasodilation, lubrication, modulation of uterine relaxation and (in males) erection.

Somatic
• Pudendal nerve S2–S4 innervates external genitalia and pelvic floor muscles; it mediates the expulsive phase of ejaculation and the voluntary sphincters.

Pain pathways (pelvic pain line)
• Visceral afferents above the peritoneal reflection (fundus, body, tubes) ascend with sympathetics to T12–L2, producing referred pain to lower abdomen and medial thigh.
• Afferents below the line (cervix, upper vagina, bladder neck, rectum) accompany parasympathetic fibres to S2–S4, localising pain to the perineum and sacral dermatomes.

Clinical Correlations and Procedures

  1. Pelvic Inflammatory Disease – pathogens ascend via patent infundibulum to the peritoneal cavity; adhesions in ampulla are a leading cause of ectopic pregnancy.
  2. Uterine Prolapse – failure of pelvic floor, fascial condensations (uterosacral, transverse cervical ligaments) or anteverted orientation permits descent of uterus and vagina.
  3. Culdocentesis – fluid in pouch of Douglas is sampled transvaginally through posterior fornix.
  4. Pap Smear – cytological scraping of the transformation zone for early detection of cervical intraepithelial neoplasia.
  5. Surgical Sterilisation – tubal ligation commonly performed at the isthmus; knowledge of vascular pedicles (mesosalpinx, suspensory ligament) prevents haemorrhage.
  6. Obstetric Anaesthesia – a caudal epidural at S2–S4 blocks pain below pelvic pain line (cervix, vagina) while sparing uterine contractions; lumbar epidural or spinal block may be required for complete analgesia.
  7. Emission vs. Ejaculation (male reference in lecture) – emission is sympathetic-mediated propulsion of seminal fluid into the prostatic urethra; ejaculation is a combined sympathetic (internal sphincter closure) and somatic (pudendal-mediated rhythmic contraction of bulbospongiosus) event.
  8. Referred Pain – visceral afferents’ route explains diffuse abdominal pain in early appendicitis or the wide radiation of cardiac pain; similarly, uterine pathology may present with lower back or thigh discomfort.