|Vein: Intercavernous sinuses|
|The sinuses at the base of the skull. (Visible as light blue circle at center.)|
|Gray's||subject #171 659|
The anterior passes in front of the hypophysis cerebri, the posterior behind it, and they form with the cavernous sinuses a venous circle (circular sinus) around the hypophysis.
The anterior one is usually the larger of the two, and one or other is occasionally absent.