Uterine and Adnexal Anatomy

Uterus

Gross Anatomy

• Pear-shaped muscular organ, ~8cm long, ~5cm wide, ~2.5cm thick (non-pregnant)
• Divisions: fundus, body, isthmus (lower uterine segment in pregnancy), cervix (supravaginal + vaginal portions)
• Normal position: anteverted (angle between cervix and vagina) and anteflexed (angle between body and cervix)

Layers

• Endometrium: functional layer (shed during menstruation) + basal layer (regenerative)
• Myometrium: three layers — outer longitudinal, middle oblique (figure-of-eight arrangement — "living ligature" after placental delivery), inner circular
• Perimetrium: serous peritoneal covering; covers anterior surface to level of isthmus (vesicouterine fold), posterior surface extends to posterior vaginal fornix (pouch of Douglas)

Blood Supply

• Uterine artery: branch of anterior division of internal iliac artery
• Crosses superior to the ureter approximately 2cm lateral to the cervix ("water under the bridge")
• Ascends along lateral uterine wall within broad ligament
• Anastomoses with ovarian artery superiorly
• Ovarian artery: from abdominal aorta (L2 level), reaches ovary via infundibulopelvic (suspensory) ligament

Venous Drainage

• Uterine veins → internal iliac veins
• Left ovarian vein → left renal vein
• Right ovarian vein → IVC directly

Uterine Supports

| Ligament | Composition | Function | |----------|-------------|----------| | Cardinal (transverse cervical / Mackenrodt's) | Fibromuscular tissue + blood vessels | PRIMARY support — from cervix/vaginal vault to pelvic side wall | | Uterosacral | Fibromuscular tissue | From cervix to sacrum; supports in sagittal plane; contain parasympathetic nerves | | Round ligament | Fibromuscular cord | From uterine horn through inguinal canal to labia majora; maintains anteversion; homologue of gubernaculum | | Broad ligament | Double peritoneal fold | Contains uterine artery, ureter, round ligament, fallopian tube; NOT a true support |

Broad Ligament Contents

• Mesosalpinx: upper portion containing the fallopian tube
• Mesovarium: posterior portion suspending the ovary
• Mesometrium: largest portion below mesosalpinx

Fallopian Tubes

• Length: approximately 10cm
• Divisions (lateral to medial):
  1. Infundibulum: funnel-shaped opening with fimbriae; captures oocyte at ovulation
  2. Ampulla: widest part; usual site of fertilisation
  3. Isthmus: narrow, thick-walled portion
  4. Interstitial (intramural): traverses the uterine wall
• Blood supply: branches of uterine and ovarian arteries via mesosalpinx
• Mucosal lining: ciliated columnar epithelium; cilia and peristalsis move oocyte/embryo toward uterus

Ovaries

• Almond-shaped, ~3cm × 2cm × 1cm
• Attached to broad ligament via mesovarium and to uterus via ovarian ligament (utero-ovarian ligament)
• Suspended from pelvic side wall by infundibulopelvic (suspensory) ligament — contains ovarian artery, vein, lymphatics, and nerves
• Surface epithelium: germinal epithelium (single layer of cuboidal cells — origin of epithelial ovarian cancers)
• Blood supply: ovarian artery (from aorta at L2) — enters via infundibulopelvic ligament

The Ureter — Three Danger Points

1. Pelvic brim: ureter crosses over the bifurcation of the common iliac artery (risk during pelvic lymphadenectomy)
2. Uterine artery crossing: 2cm lateral to the cervix at the base of the broad ligament ("water under the bridge" — risk during hysterectomy)
3. Vesicouterine ligament / bladder insertion: as ureter enters the bladder base (risk during anterior colporrhaphy or radical hysterectomy)

• Right ureter runs close to the appendix and caecum
• Both ureters pass through the parametrium
• During hysterectomy: identify and protect the ureters before clamping uterine vessels

Pouch of Douglas (Rectouterine Pouch)

• Deepest point of the peritoneal cavity in the female
• Between posterior uterine surface and anterior rectum
• Clinically accessible via posterior vaginal fornix (culdocentesis)
• Common site for: endometriosis deposits, pelvic fluid collection, ovarian cancer deposits

Important Facts for MRCOG

• Uterine artery crosses ABOVE the ureter 2cm lateral to cervix
• Cardinal ligaments provide PRIMARY uterine support
• Round ligament: passes through inguinal canal to labia majora
• Left ovarian vein → left renal vein; right ovarian vein → IVC
• Ampulla of fallopian tube: usual site of fertilisation; most common site for ectopic pregnancy
• Three danger points for ureter during pelvic surgery
• Ovarian blood supply enters via infundibulopelvic ligament — must be ligated during oophorectomy
• Pouch of Douglas: deepest peritoneal point, accessed via posterior fornix

Clinically reviewed by NHS obstetricians and gynaecologists

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