E, The sutures have been forced open to show the relationship of the foramen to the petroclival and occipitomastoid sutures. The jugular foramen has a larger lateral part, the sigmoid part, which receives the drainage of the sigmoid sinus, and a smaller medial part, the petrosal part, which receives the drainage of the inferior petrosal sinus. The intrajugular process of the occipital bone is somewhat more prominent than shown in C and projects forward toward the intrajugular process of the temporal bone. The hamate process normally extends along the medial edge of the petrosal part of the foramen to the adjacent part of the temporal bone, but in this case the sutures were forced open, leaving an interval between the hamate process and the temporal bone. F, Enlarged view. G, The intrajugular process of the temporal bone projects into the interval between the sigmoid and petrosal parts of the foramen. A ridge, the intrajugular ridge, extends forward from the intrajugular process along the medial side of the jugular bulb. The glossopharyngeal nerve passes forward along the medial side of the intrajugular process and ridge. The vagus and accessory nerves enter the dura on the medial side of the process, but quickly descend and do not pass forward along the medial edge of the ridge as does the glossopharyngeal nerve. The jugular process of the occipital bone often has a small prominence on its surface that projects toward the intrajugular process of the temporal bone, and in some foramina, the intrajugular processes of the two bones are joined by an osseous bridge that converts the foramen into two osseous foramina. In this case, the intrajugular process of the occipital bone is absent. H, Enlarged view. The cochlear aqueduct opens above the petrosal part of the foramen and the site where the glossopharyngeal nerve enters the intrajugular part of the foramen on the medial side of the intrajugular process. The vestibular aqueduct opens onto the posterior surface of the temporal bone superolateral to the jugular foramen. (Images courtesy of AL Rhoton, Jr.)