Anatomical sphincter of fallopian tubes :
The intramural pa is the innermost pa of the fallopian tube which traverses the myometrium to open into endometrial cavity. It is the shoest pa length being 18 mm and narrowest pa with internal diameter being 1mm or less so that only finest cannula can be passed through it during salpingostomy operation. Ref: Shaw's Textbook of Gynaecology, 15th edition, page no: 11
Infundibulum
Isthmus
Intramural
Ampulla
Anatomy of the female genital tract