Topography of Female Pelvic Organs

Bony framework: greater and lesser pelvis

The pelvic bones and sacrum form a closed bony ring — the pelvis. The female pelvis has distinct sexual dimorphism: it is wider and shorter than the male pelvis, and the iliac wings are more flared and positioned more vertically. The pelvic inlet in women is larger and narrows less inferiorly.

• The greater pelvis is bounded by the fifth lumbar vertebra posteriorly and the iliac wings laterally.
• The lesser pelvis is a tapering bony canal. Its walls are formed by the pelvic surface of the sacrum and coccyx, the pubic and ischial bones, as well as the obturator membranes, sacrospinous and sacrotuberous ligaments.

Dimensions of the female pelvis:

External genitalia (vulva)

Structures located outside the lesser pelvis cavity (genitalia externa, or vulva) include the mons pubis, labia majora and minora, clitoris (clitoris), and the vestibule of the vagina.

Mons pubis (mons pubis) occupies the lower part of the anterior abdominal wall directly above the pubic symphysis. In adult women, this area is covered with hair and has a well-developed fat pad of subcutaneous tissue.

Topographically, several important landmarks are distinguished in this region:

1. Labia majora (labium majus pudendi)
2. Labia minora (labium minus pudendi)
3. Anterior and posterior vaginal walls (paries anterior et posterior vaginae)
4. Vaginal orifice (ostium vaginae) with the free margin of the hymen (hymen)
5. External urethral orifice (ostium urethrae externum)
6. Perineum (perineum), separating the genital tract from the anus (anus)

Muscles and fascia of the perineum

The perineum closes the pelvic outlet and includes the urogenital diaphragm and the anal region. This area also contains the internal pudendal artery, superficial transverse perineal muscle, ischiocavernosus and bulbospongiosus muscles, as well as the sphincter muscles of the urethra and vagina.

• Urogenital diaphragm consists of fused fascial layers stretched between the pubic bones. Within its thickness lies the deep transverse perineal muscle, which originates from the inner surface of the lower margin of the pubic symphysis and blends into the perineal body of the vagina.
• Anal region contains the rectal sphincter, whose fibers converge at the tendinous center of the perineum, and the anococcygeal ligament.

The deepest layer of the pelvic floor is the levator ani muscle (m. levator ani). It consists of three paired portions:

• Pubococcygeus muscle (m. pubococcygeus) — its medial fibers closely encircle the urogenital hiatus, urethra, and vagina.
• Iliococcygeus muscle (m. iliococcygeus) — forms the middle part of the muscular layer.
• Ischiococcygeus muscle (m. ischiococcygeus).

Class and exam questions

What else to study on this topic

• Instrumental (ultrasound) and laboratory (hormones) diagnostics of gonadal function
• Ovarian developmental anomalies (congenital hypoplasia and aplasia)
• Chromosomal aberrations and their impact on somatic traits (Turner, Klinefelter, and Triple X syndromes)
• Disorders of sex development: true and pseudohermaphroditism
• Male genital developmental anomalies (cryptorchidism, monorchism) and their clinical consequences

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.