The infundibulum is the part of the fallopian tube which is funnel-shaped and an opening near the ovary and to which fimbriae( Finger-like ciliated projections) is attached.
The isthmus is also a part of the fallopian tube which is a narrow section of the uterine tube connecting the ampulla to the uterine cavity.
The ampulla is a part of the fallopian tube which is the widest section of the uterine tubes and the fertilisation usually occurs in this part.
Ectopic pregnancy is a medical emergency. If the lumen of the uterine tube is partially occluded then the sperm may pass through to fertilise the ovum. anyhow the fertilised egg is unable to pass into the uterus and thus implant the uterine tube. this is known as an ectopic pregnancy.