Cervix

Description

Bisected in the midsagittal plane, the cervix uteri is presented as the inferior, cylindrical portion of the uterus, continuous superiorly with the uterine body at the isthmus and projecting inferiorly toward the vagina. The cervical canal runs longitudinally between the internal os at the uterine cavity and the external os opening into the vaginal lumen, with anterior and posterior lips of the portio vaginalis framing the ectocervical margin. Anterior relationships place the cervix close to the bladder base, while the posterior cervical surface faces the rectouterine pouch region. This midline division clarifies the functional transition from endocervix to ectocervix and the anatomic bottlenecks that matter in practice. The internal os is the key landmark for cervical insufficiency and for defining the upper extent of the cervical canal in transvaginal ultrasound and cerclage planning, while the external os and transformation zone guide sampling in Pap and HPV screening and colposcopy-directed biopsy. Orientation in sagittal section also matches how clinicians mentally map the path of a uterine sound, IUD inserter, or hysteroscope passing through the endocervical canal into the uterine cavity. Small space, big consequences. Use this artwork in gross anatomy and pelvic anatomy teaching to anchor spatial understanding of the cervix within the sagittal female pelvis, and in OB-GYN training materials covering cervical length assessment, labor-related cervical change (effacement and dilation), and common procedures such as endometrial biopsy, IUD placement, and dilation and curettage. It also supports patient-facing and editorial graphics explaining the internal and external os and why lesions at the transformation zone are targeted in cervical cancer screening. Anatomical accuracy verified by SciePro's Medical Advisory Board.