What is one of the borders of the pelvic inlet?

The sacral promontory is one of the key anatomical features that defines the border of the pelvic inlet. It is located at the anterior edge of the sacrum and serves as a prominent landmark that helps to delineate the boundary between the abdominal cavity and the pelvic cavity.

In obstetrics and gynecology, recognizing the pelvic inlet is crucial because it plays a significant role during labor and delivery. The dimensions of the pelvic inlet can influence the course of labor, the baby’s descent, and the mode of delivery.

Other structures, such as the iliac crest or the pubic arch, do not form part of this specific boundary. The iliac crest is positioned higher in the pelvis and is not directly involved in defining the inlet. The pubic arch, although important in the overall structure of the pelvis, also lies below the pelvic inlet, influencing the shape of the outlet instead. The coccyx is located at the very bottom of the pelvis and does not contribute to the pelvic inlet. Thus, the sacral promontory remains the correct answer as it is anatomically and functionally integral to the pelvic inlet's definition.