What is the narrowest part of the Fallopian tube?

Appeared in: UP CHO - 2018

Explanation

The interstitial portion, also called the intramural part, is the segment of the fallopian tube that passes through the muscular wall of the uterus (myometrium).
Due to its location within the thick uterine muscle, this part has the smallest diameter of all the segments.
Its lumen is approximately 1 mm wide, making it the narrowest section of the tube.

Option A: The ampulla is the widest and longest part of the fallopian tube, not the narrowest.
Option B: The isthmus is a narrow, thick-walled portion of the tube, but it is not the narrowest part. The interstitial portion is narrower.
Option C: The infundibulum is the funnel-shaped distal end of the fallopian tube that opens into the peritoneal cavity near the ovary. It is characterized by fimbriae and is not the narrowest part.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy of the Fallopian Tube as background academic context rather than a clinical decision trigger.
Understanding the anatomy of the fallopian tube is crucial for diagnosing and managing conditions like ectopic pregnancy and infertility.
An interstitial ectopic pregnancy is a medical emergency. Nurses must be vigilant for signs of shock (hypotension, tachycardia, pallor) in a patient with a suspected ectopic pregnancy, as rupture in this location can lead to rapid, massive internal bleeding.
What if? If a patient has a history of pelvic inflammatory disease (PID), the risk of tubal blockage and ectopic pregnancy increases. The inflammation can cause scarring and narrowing (stenosis) in any part of the tube, but obstruction of the narrow isthmus or interstitial part can prevent a fertilized egg from reaching the uterus.

How to Approach the Question

This is a factual recall question based on anatomy.
First, identify the core of the question: it asks for the 'narrowest part' of the 'Fallopian tube'.
Mentally (or by sketching) recall the four segments of the fallopian tube in order from the ovary to the uterus: Infundibulum -> Ampulla -> Isthmus -> Interstitial portion.
Recall the key characteristic of each part's diameter: the ampulla is the widest, the isthmus is narrow, and the interstitial part is the very last segment that passes through the uterine wall, making it the narrowest.
Compare this anatomical knowledge with the given options to select the correct answer.

Concept Tested & Keywords

QofkJIRC8z8lNpHtP2lX3P

E6 Anatomy Applied Ashalatha 4e p. 389-391

Practise the full UP CHO - 2018

Attempt every question from this paper in a timed mock, then review the full solution for each one.