The anatomical and histological internal os is the isthmus

  1. Anatomical Internal Os:
  • The anatomical internal os is the opening between the uterine cavity and the cervical canal. It marks the transition from the broader uterine cavity to the narrower cervical canal. This opening is a part of the cervix, which is the lower part of the uterus.
  1. Isthmus:
  • The isthmus, in the context of the female reproductive system, typically refers to a narrow region or constriction in an organ. It is not specifically associated with the transition between the uterine cavity and the cervical canal. In the context of the uterus, the term isthmus is sometimes used to describe the narrow region of the uterus located between the body of the uterus and the cervix.

It’s important to note that the anatomical internal os and the isthmus are not the same structures. The anatomical internal os is a specific opening, while the isthmus is a term that generally describes a narrowed region in an organ. In the context of the uterus, the isthmus is not the same as the anatomical internal os.