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MBBS Human Anatomy - Paper II Answer
Clinical Scenario Recap
A 52-year-old multiparous woman with a history of difficult vaginal deliveries presents with a feeling of something coming down the vagina on straining, with a prolapsing mass found on PV examination.
a. Clinical Diagnosis
Uterine Prolapse (Uterovaginal Prolapse)
The mass prolapsing into the vagina is the uterus. This is strongly supported by:
- Multiparous woman (multiple vaginal deliveries weaken the pelvic floor)
- Increased intra-abdominal pressure (coughing, sneezing, lifting) exacerbates descent
- History of difficult vaginal deliveries (stretched/torn pelvic supports)
- Age 52 years (peri/postmenopausal - reduced estrogen weakens connective tissue supports)
b. Normal Position of the Uterus
The uterus normally lies in the midline of the pelvic cavity, between the urinary bladder anteriorly and the rectum posteriorly.
Its normal position is described as:
- Anteverted - the long axis of the uterus forms an angle of ~90° with the vagina (tilts forward over the bladder)
- Anteflexed - the body of the uterus bends forward on the cervix at an angle of ~170°
The fundus and body thus lie above the bladder, with the cervix pointing downward and backward toward the posterior vaginal wall.
c. Parts and Relations
Parts of the Uterus
| Part | Description |
|---|---|
| Fundus | Rounded superior end, above the openings of the uterine tubes |
| Body (Corpus) | Flattened anteroposteriorly; contains the uterine cavity (inverted triangle shape) |
| Isthmus | Narrow junction between body and cervix (lower uterine segment) |
| Cervix | Cylindrical lower portion; has an exocervix (portio vaginalis) and endocervical canal |
The endometrial cavity is triangular, continuous superiorly with the uterine tubes at the cornu and inferiorly with the cervical canal at the internal os.
Relations
| Direction | Structure |
|---|---|
| Anteriorly | Vesicouterine pouch (peritoneal pouch) above; bladder/isthmus below |
| Posteriorly | Rectouterine pouch (Pouch of Douglas) with the rectum behind it |
| Superiorly | Uterine tubes project laterally; small intestine loops may lie on the fundus |
| Inferiorly | Cervix projects into the vagina; vaginal fornices surround the cervix |
| Laterally | Broad ligament, uterine arteries, and ureters (ureters pass ~2 cm lateral to the cervix - surgically important) |
Peritoneum covers the fundus and body anteriorly down to the isthmus, and the entire posterior surface including the posterior cervix. Laterally, the broad ligament (double peritoneal fold) encloses the neurovascular supply.
d. Supports of the Uterus
The uterus is held in position by ligamentous supports (main) and muscular/fascial supports (primary/most important).
I. Primary Support - Pelvic Floor (Most Important)
- Levator ani muscles (pubococcygeus, iliococcygeus, puborectalis) - the main muscular support forming the pelvic diaphragm
- Perineal body - central fibromuscular node at the centre of the perineum
- Perineal membrane (urogenital diaphragm)
II. Ligamentous (Fascial Condensation) Supports
These are condensations of pelvic fascia around the cervix and vaginal vault:
| Ligament | Direction | Importance |
|---|---|---|
| Transverse cervical (Cardinal/Mackenrodt's) ligaments | Lateral - from cervix/vaginal vault to pelvic wall | Most important - main support preventing prolapse |
| Uterosacral ligaments | Posterior - from cervix to sacrum (S2-S4) | Keep cervix pulled posteriorly; important support |
| Pubocervical ligaments | Anterior - from cervix to pubis | Anterior support |
| Round ligaments | Anterolateral - from fundus to inguinal canal/labia majora | Maintain anteversion but provide weak support (not fibrous - cannot prevent prolapse) |
| Broad ligament | Bilateral double peritoneal fold | Encloses vessels and tubes; minimal mechanical support |
In prolapse, the cardinal and uterosacral ligaments are primarily stretched/torn, compounded by levator ani damage from difficult deliveries.
e. Blood Supply
Arterial Supply
The uterus receives blood mainly from the uterine artery, with anastomoses from the ovarian and vaginal arteries.
Uterine artery:
- Branch of the anterior trunk of the internal iliac artery
- Courses medially in the base of the broad ligament toward the cervix
- Crosses the ureter (ureter passes underneath - "water under the bridge") approximately 2 cm lateral to the cervix - a critical surgical landmark in hysterectomy
- Passes superior to the lateral vaginal fornix
- Ascends along the lateral margin of the uterus to the uterine tube level
- Curves laterally to anastomose with the ovarian artery
Summary of arterial supply:
| Artery | Origin | Area Supplied |
|---|---|---|
| Uterine artery | Internal iliac (anterior trunk) | Main supply - body, cervix, upper vagina |
| Ovarian artery | Abdominal aorta (L2) | Fundus, uterine tubes, ovary (anastomoses with uterine a.) |
| Vaginal artery | Internal iliac | Lower uterus/cervix |
Venous Drainage
- Uterine veins drain into the internal iliac veins via the uterine venous plexus
Lymphatic Drainage
- Fundus/upper body: Para-aortic lymph nodes (follows ovarian vessels)
- Body: Internal and external iliac lymph nodes
- Cervix: Internal iliac, external iliac, obturator, and sacral lymph nodes
Diagram recommendation: Draw the uterus in sagittal section showing the anteflexed/anteverted position, label all parts, show the cardinal and uterosacral ligaments in a coronal/superior view, and draw the uterine artery crossing the ureter.
(Sources: Gray's Anatomy for Students, Berek & Novak's Gynecology)
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