Narrowest part of the fallopian tube is the
A. Interstitial
B. Isthmus
C. Infundibulum
D. Ampulla
Correct Options: A. Interstitial
Explanation: The narrowest part of the fallopian tube is the interstitial (intramural) part.
Fallopian tube parts (from lateral to medial):
1. Infundibulum
2. Ampulla – widest part
3. Isthmus
4. Interstitial (intramural) – narrowest, passes through the uterine wall
So while the isthmus is narrow, the interstitial part is the narrowest overall.
Final answer: Interstitial (intramural) part.
Other Options Details
Here are descriptions for each term:
A. Interstitial
• Location: It is the portion of the fallopian tube that lies within the muscular wall (myometrium) of the uterus.
• Characteristics: It is the narrowest and shortest part of the tube.
• Function: Acts as the entry pathway where the fallopian tube opens into the uterine cavity.
B. Isthmus
• Location: Just next to the interstitial part, extending laterally from the uterus.
• Characteristics: It is a narrow, straight segment of the fallopian tube.
• Function: It helps transport the fertilized ovum or sperm and is highly muscular.
C. Infundibulum
• Location: The funnel-shaped distal end of the fallopian tube.
• Characteristics: It has finger-like projections called fimbriae.
• Function: Captures the released ovum from the ovary during ovulation.
D. Ampulla
• Location: Between the infundibulum and isthmus.
• Characteristics: It is the widest and longest portion of the fallopian tube.
• Function: Most common site of fertilization (union of sperm and ovum).
Summary Table
Part Description Key Feature Function
Interstitial Part inside uterine wall Narrowest Connects tube to uterus
Isthmus Narrow segment after interstitial Muscular Transport
Ampulla Wide, long mid-portion Widest Site of fertilization
Infundibulum Funnel near ovary Fimbriae Picks up ovum
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Writer: Vandita Singh, Lucknow (GS India Nursing Group)