Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
The uterine isthmus is the inferior-posterior part of uterus, on its cervical end — here, the uterine muscle (myometrium) is narrower and thinner. It connects the body and cervix.
The uterine isthmus can become more compressibile in pregnancy, which is a finding known as Hegar's sign.