The Uterus

A. Definition & Parts (2 marks)

• Perimetrium (serosa) — outer peritoneal coat
• Myometrium — middle, thick smooth muscle layer (three indistinct layers)
• Endometrium — inner mucosa, divided into stratum functionalis (shed at menstruation) and stratum basalis (permanent, regenerates cyclically)

B. Relations (3 marks)

Anterior Relations

• The vesicouterine pouch (of peritoneum) intervenes between the anterior surface of the uterus and the superior (posterior) surface of the urinary bladder. The peritoneum reflects off the bladder onto the uterus at the level of the isthmus (internal os).
• Below the level of the vesicouterine pouch, the supravaginal cervix is directly applied to the base of the bladder with only loose connective tissue (paracervical fascia) between them.

Posterior Relations

• The posterior surface of the uterus is covered by peritoneum all the way down to the posterior fornix of the vagina, forming the rectouterine pouch (Pouch of Douglas) — the deepest point of the female peritoneal cavity.
• The rectum lies posterior to the rectouterine pouch.
• The rectouterine folds (uterosacral ligaments) bound the pouch laterally.

Superior Relations

• The uterine (fallopian) tubes enter laterally at each uterine cornu.
• The small intestine may lie above the fundus.

Lateral Relations

• The broad ligaments extend laterally from each side to the pelvic sidewall.
• The uterine artery runs in the base of the broad ligament, crossing superior to the ureter ("bridge over water" relationship) — the ureter passes approximately 1.5 cm lateral to the supravaginal cervix.
• The ureter is at risk of injury during hysterectomy here.
• The ovaries and uterine tubes lie within the broad ligament.

Inferior Relations

• The cervix is continuous inferiorly with the vagina at the vaginal fornices.
• The anterior fornix is related to the base of the bladder; the posterior fornix is related to the rectouterine pouch (clinically accessible by needle aspiration through the vagina).

C. Supports (4 marks)

I. Primary (Mechanical) Supports — the Pelvic Floor

• The pelvic diaphragm (levator ani + coccygeus) forms the main structural floor supporting the uterus indirectly via the vagina.

II. Ligamentous Supports

a. Cardinal Ligaments (Mackenrodt's / Transverse Cervical Ligaments) ★ Most Important

• Condensations of parametrial fascia and smooth muscle at the base of the broad ligament
• Extend from the lateral cervix and vaginal vault → lateral pelvic wall (pelvic fascia/pelvic diaphragm)
• The main supporting ligaments against uterine prolapse — support the cervix and upper vagina
• Contain the uterine artery and ureter runs just below

b. Uterosacral Ligaments

• Arise from the posterior upper cervix → arch posterolaterally around the rectum → insert into S2–S4 sacral periosteum/fascia
• Form a visible peritoneal fold (rectouterine fold) framing the Pouch of Douglas
• Support the cervix and maintain anteversion; interdigitate with cardinal ligament fibers near the cervix
• Contain the inferior hypogastric (pelvic) autonomic nerve plexus

c. Round Ligaments

• Arise from the uterine cornu (just anterior to uterine tube entry) → pass through the inguinal canal → insert in the labium majus
• Maintain anteversion (prevent backward tipping) but are weak supports — stretch significantly in pregnancy
• Represent the remnant of the gubernaculum

d. Broad Ligaments

• Double-layered peritoneal folds extending from each side of the uterus to the lateral pelvic wall
• Divide the pelvis into vesicouterine pouch (anterior) and rectouterine pouch (posterior)
• Contain: uterine tubes (mesosalpinx), ovaries (mesovarium), round ligament, ovarian ligament, uterine vessels, ureter, lymphatics, and nerves
• Provide minimal mechanical support — mainly a peritoneal covering

e. Pubocervical Ligaments

• Pass from the cervix → behind the pubic symphysis
• Provide anterior support to the cervix

Summary Table

D. Clinical Anatomy (1 mark)