Female Pelvic Anatomy & Sonography – Review Flashcards

Objectives

• Understand gross bony anatomy, musculature, visceral anatomy, relational anatomy, and sonographic appearances of the female pelvis.
• Be able to describe each organ, ligament, space, muscle, and bony landmark in relation to adjacent structures and to imaging planes.
• Recognize normal variants (e.g.
  • anteverted-anteflexed vs retroverted-retroflexed uterus).
• Memorize normal size ranges and vascular supply of reproductive organs.
• Appreciate which imaging modality (US, MRI, CT) is most appropriate for different clinical questions.

Gross Bony Anatomy of the Female Pelvis

• Pelvis divided by the linea terminalis into:
  • False (greater) pelvis – superior to linea terminalis.
  • True (lesser) pelvis – inferior (deep) to linea terminalis.
• Key osseous landmarks (video 3.4.1):
  • Iliac crests, pubic arch, ischiopubic rami, body of ischium, ischial spine, ischial tuberosity.
  • Sciatic notch, obturator foramen (closed by obturator membrane).
• Male vs female pelvis compared: female pelvis has wider pelvic inlet, broader pubic arch (>$80^{\circ}$), lighter bones.

Pelvic Musculature

Muscles of the Pelvic Wall (video 3.4.4)

• Piriformis – from sacrum to greater trochanter; exits via greater sciatic foramen.
• Obturator internus – covers obturator foramen; tendon makes a right-angle turn to femur.
• Tendinous arch – thickened fascia on obturator internus; origin for part of levator ani.

Pelvic Diaphragm (video 3.4.5)

• Forms floor of true pelvis; supports viscera.
• Components (paired unless stated):
  • Levator ani
  • Pubococcygeus
  • Iliococcygeus
  • Puborectalis (sometimes listed separately)
  • Coccygeus (ischiococcygeus) – posterior small triangular muscle.
• Openings:
  • Urogenital hiatus – urethra + vagina.
  • Anal hiatus – anal canal.
• Anococcygeal ligament – midline fibrous tissue posterior to anal canal.
• Ischiorectal (ischio-anal) fossa – fat-filled space lateral to anal canal.

Surface / Sonographic Correlate

• Muscles appear hypoechoic with echogenic striations; seen in transverse pelvic images surrounding pelvic organs.

True vs False Pelvis (Tabulated)

• TRUE PELVIS
  • Location: below linea terminalis.
  • Outer boundaries: pelvic bones, obturator internus + piriformis + pelvic diaphragm (pubococcygeus, iliococcygeus, coccygeus).
  • Contents: genital tract (uterus, vagina, Fallopian tubes), ovaries, urinary bladder, pelvic colon.
• FALSE PELVIS
  • Location: above linea terminalis.
  • Boundaries: iliac crests, iliopsoas, rectus abdominis, transversus abdominis.
  • Contents: lower abdominal viscera – ileum, sigmoid colon.

Female Pelvic Ligaments

• Broad ligament – double fold of peritoneum; anterior/posterior reflections over uterus extending laterally; supports tubes, round & ovarian ligaments, blood vessels; subdivided:
  • Mesometrium – adjacent to uterus.
  • Mesosalpinx – adjacent to tube.
  • Mesovarium – attaches ovary to broad ligament.
• Round ligament of uterus – from uterine cornua through inguinal canal to labia majora; maintains anteflexion.
• Cardinal (transverse cervical) ligament – cervix/isthmus to lateral walls; strong cervical support.
• Uterosacral ligament – posterior cervix to sacrum; maintains uterine axis.
• Suspensory (infundibulopelvic) ligament – lateral ovary/fimbrial end to pelvic wall; conveys ovarian vessels; positions ovary.
• Ovarian ligament – ovary’s medial pole to uterine cornua.
• Pubovesical / pubocervical fascia – bladder neck to pubic bones; fuses with tendinous arch.

Pelvic Peritoneal & Extraperitoneal Spaces

• Anterior cul-de-sac (vesicouterine pouch) – peritoneal reflection between bladder and uterus.
• Posterior cul-de-sac (rectouterine pouch, pouch of Douglas) – deepest peritoneal recess; between uterus and rectum.
• Space of Retzius (retropubic space) – fat-filled space between pubic symphysis and anterior bladder wall.
• Genital tract compartments – vagina occupies hypogastric portion; cervix enters at right angle.

Uterus – Gross Anatomy

• Sits in true pelvis between bladder (anterior) & rectum (posterior).
• Wall layers:
  • Endometrium (mucosa, echogenic line on US).
  • Myometrium (smooth muscle; homogeneous, mid-level echogenicity on US; subdivided into inner, middle, outer zones; arcuate vessels in middle layer).
  • Serosa (perimetrium) – visceral peritoneum.
• Segments:
  • Fundus – superior to tube entry; no cavity.
  • Body – triangular cavity from tubes to isthmus.
  • Isthmus / Lower uterine segment (LUS) – narrow zone between body & cervix (important in obstetrics).
  • Cervix – fusiform canal; subdivided into supravaginal & vaginal parts; ends at external os.

Uterine Positions

• Anteverted-Anteflexed (most common):
  • Anteversion – long axis of uterus tilted anterior to vaginal axis.
  • Anteflexion – body flexed anterior on cervix.
• Retroverted-Retroflexed – uterus tilted or flexed posteriorly into rectouterine pouch.
• Clinical relevance: position affects IUD placement, sonographic windows, infertility workup.

Os Anatomy

• Internal os – junction body ↔ cervical canal.
• External os – cervix ↔ vagina; shape:
  • Circular in nulliparous; transverse slit in multiparous (anterior/posterior lips).

Relations

• Fundus/body/supravaginal cervix:
  • Anterior – superior surface of bladder.
  • Posterior – sigmoid colon.
  • Lateral – uterine arteries.
• Vaginal cervix surrounded by fornices:
  • Anterior fornix (bladder side).
  • Posterior fornix (rectouterine pouch access for culdocentesis).
  • Two lateral fornices (ureter relations).

Vagina

• Fibromuscular tube $\approx 9\ \text{cm}$ (anterior wall $7.5\ \text{cm}$, posterior $9\ \text{cm}$).
• Extends from external os to vulvar introitus; encircles cervix forming anterior, posterior, lateral fornices.
• Functions: copulatory organ, birth canal.
• Relations (pelvis):
  • Anterior – bladder & urethra.
  • Posterior – rectum & anal canal.
  • Lateral – ureters at lateral fornix.

Fallopian (Uterine) Tubes

• Length $\approx 10\ \text{cm}$; enclosed in broad ligament.
• Parts (medial → lateral):
  • Intramural (interstitial) – within uterine wall.
  • Isthmus – narrowest region.
  • Ampulla – widest, tortuous; fertilization site.
  • Infundibulum – funnel with fimbriae draped over ovary.
• Functions: fertilization & transport of embryo to uterus.

Ovaries

• Almond-shaped; attached to posterior broad ligament by mesovarium.
• Medial pole tethered to uterus by ovarian ligament; lateral pole continuous with fimbriae, suspended by infundibulopelvic ligament.
• Functions: oogenesis & secretion of estrogen/progesterone.

Vascular Supply

• Ovarian arteries – direct aortic branches (just below renal arteries). Right & left.
• Uterine artery – branch of internal iliac; gives:
  • Tubal, ovarian, cervicovaginal, ureteral branches; anastomoses with ovarian artery.
• Venous drainage to ovarian veins & uterine plexus.

Normal Organ Dimensions (mean adult values)

• Vagina – length $9\ \text{cm}$.
• Cervical canal – $2{-}4\ \text{cm}$.
• Uterus
  • Premenarche: $2.5\times2\times1\ \text{cm}$.
  • Nulliparous: $7\times4\times3\ \text{cm}$.
  • Multiparous: $8.5\times5.5\times4.5\ \text{cm}$.
• Fallopian tube – $7{-}12\ \text{cm}$.
• Ovary – $2.5{-}5.0\ \text{cm}$ length × $1.0{-}3.0\ \text{cm}$ width × $0.6{-}2.2\ \text{cm}$ thickness.

Sonographic Appearance & Imaging Planes

Modalities

• Ultrasonography (TA & TV) – first-line; dynamic, no ionizing radiation.
• MRI – superior soft-tissue contrast; staging malignancy.
• CT – trauma, staging; ionizing radiation.

Transabdominal (TA) US

• Longitudinal image: bladder (acoustic window) anterior; uterus (fundus → cervix) seen; myometrium homogeneous, endometrium central echogenic stripe.
• Transverse image: uterus appears circular; surrounding levator ani, rectum posterior.

Transvaginal (TV) US – Sagittal Plane

• Probe apex (near field) maps to inferior/posterior pelvis; far field = anterosuperior.
• Provides magnified detailed view of uterine layers; fills screen.

TV – Coronal (Short-axis) Plane

• With anteverted uterus, coronal shows short axis of fundus; near field maps inferolateral pelvis; far field maps superolateral.

Layer Identification (TV)

• Outer myometrium hypoechoic; middle myometrium with arcuate vessels; inner myometrium (junctional zone) slightly hypoechoic; endometrium echogenic double line.
• Example measurement: $\text{Ut-L}=8.30\,\text{cm},\ Ut-H=4.42\,\text{cm}$.

Clinical / Practical Connections

• Knowledge of uterine position important during catheter placement (IUI, embryo transfer) and avoiding uterine perforation.
• Posterior cul-de-sac fluid on US can indicate ovulation, PID, ruptured ectopic, etc.
• Ligament integrity influences uterine prolapse pathophysiology.
• Understanding muscle locations prevents confusion with masses on imaging (e.g., recognizing piriformis vs ovarian pathology).

Summary Checklist for Exam Review

• Identify all bony landmarks on a pelvis model.
• Trace course of uterine & ovarian arteries; recall anastomoses.
• Draw broad ligament subdivisions; attach tube & ovary.
• List pelvic diaphragm muscles + hiatus contents.
• Memorize organ size ranges & normal sonographic appearance.
• Practice probe orientation: match image apex to anatomy (TV vs TA).
• Recall peritoneal spaces and likely fluid collection sites.
• Differentiate anteversion/anteflexion vs retroversion/retroflexion in diagrams & imaging.