What is the isthmus of the uterus?

• A. Neck-like portion between body and cervix
• B. Narrow portion between body and cervix
• C. Area between uterine tube entrance superiorly and the isthmus inferiorly
• D. Thick wall of smooth muscle and connective tissue

Answer: (B)

The isthmus is the narrow portion that connects the main body of the uterus to the cervix. It sits just above the cervix and marks the transition from the thick-walled body (the corpus) to the cervical region. This description—being the narrow segment between the body and the cervix—best fits what the isthmus is. The other options either describe the cervix itself (the neck-like portion), the area higher up in the body, or the myometrium as a whole rather than a distinct region.