Uterus, Cervix and Fallopian Tube Anatomy and Histology
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Direct answer
The uterus has three wall layers: a perimetrium, a thick myometrium and a cyclically changing endometrium. The cervix has a mucus-secreting endocervix and a squamous ectocervix that meet at the transformation zone, while the fallopian tube is a paired duct whose ciliated and secretory lining carries the ovum toward the uterus. These layers explain where ectopic pregnancy and tubal sterilisation take place.
What you must remember
- Parts of the uterus: fundus, body, isthmus and cervix, with the adult cervix about 3 cm long and lying below the isthmus.
- Myometrium: thick smooth muscle with outer longitudinal, middle vascular and inner layers; the interlacing middle layer compresses vessels after delivery and so controls bleeding.
- Endometrium: functionalis and basalis layers over a stroma containing spiral arteries; the functionalis is shed at menstruation and the basalis regenerates it.
- Endocervix: lined by tall, mucus-secreting columnar epithelium that forms the cervical plug.
- Ectocervix: covered by non-keratinised stratified squamous epithelium that meets the endocervix at the squamocolumnar junction.
- Fallopian tube: divided into infundibulum with fimbriae, ampulla, isthmus and intramural part; the ampulla is the usual site of fertilisation.
- Tubal histology: ciliated and secretory (peg) cells line the mucosa, with cilia beating towards the uterus and the muscular coat aiding transport.
- Uterine blood supply: the uterine artery arises from the anterior division of the internal iliac artery and crosses the ureter near the cervix.
Mapping the epithelia to clinical sites
Each segment lines a different surface, and the lining predicts both the disease and the procedure. The table compares the epithelia that exam questions link to clinical sites, and each row pairs a lining with the problem most often tested against it.
| Segment | Lining | Clinical link |
|---|---|---|
| Endometrium | Simple columnar, ciliated and secretory | Menstruation and implantation |
| Endocervix | Tall mucus-secreting columnar | Cervical mucus and glandular neoplasia |
| Ectocervix | Non-keratinised stratified squamous | Most squamous cervical cancers |
| Fallopian tube | Ciliated and secretory (peg) cells | Ampullary ectopic pregnancy |
| Myometrium | Smooth muscle, no epithelium | Atony and postpartum haemorrhage |
The transformation zone, the area between the original and the new squamocolumnar junction, is where most cervical precancer arises, and it shifts position with age and after childbirth. Tubal cilia carry the ovum, so infection that damages them raises the risk of tubal blockage and ectopic pregnancy. Surgeons rely on these relations when they ligate the uterine artery at hysterectomy or identify the tube at sterilisation.
Where the exam tries to catch you
Anatomy questions on the uterus and tube often hinge on a few specific details.
- Trap: Placing most ectopic pregnancies in the fimbriae. Correct: The ampulla is the commonest site, followed by the isthmus, and fimbrial implantation is less frequent.
- Trap: Calling the endocervix squamous like the ectocervix. Correct: The endocervix is tall mucus-secreting columnar epithelium, while the ectocervix is non-keratinised squamous epithelium.
- Trap: Assuming the uterine artery arises from the abdominal aorta. Correct: It comes from the anterior division of the internal iliac artery and crosses the ureter near the cervix, which matters at hysterectomy.
Frequently asked questions
Where does most tubal ectopic pregnancy occur?
Most tubal ectopic pregnancies occur in the ampulla, the widest and most common site of fertilisation. The isthmus is the next most common site, while interstitial implantation is rare.
Which epithelium lines the endocervix?
The endocervix is lined by a single layer of tall, mucus-secreting columnar epithelium. This mucus forms the cervical plug and changes in consistency across the menstrual cycle.
What is the squamocolumnar junction in gynaecology?
The squamocolumnar junction is where the ectocervix's squamous epithelium meets the endocervix's columnar epithelium. The transformation zone is the metaplastic area around it, and most cervical precancer arises there, which is why it is the focus of screening and colposcopy.
Where is tubal sterilisation usually performed?
Tubal sterilisation is usually performed on the mid-isthmic segment, which is narrow, easy to isolate and least likely to fail. Methods include Pomeroy ligation and the application of a Falope ring.