The<unk>  are of large size and begin at the internal occipital protuberance; one, generally the right, being the direct continuation of the superior sagittal sinus, the other of the straight sinus. Each<unk>  sinus passes lateral and forward, describing a slight curve with its convexity upward, to the base of the petrous portion of the temporal bone, and lies, in this part of its course, in the attached margin of the tentorium cerebelli; it then leaves the tentorium and curves downward and medialward (an area sometimes referred to as the sigmoid sinus) to reach the jugular foramen, where it ends in the internal jugular vein. In its course it rests upon the squama of the occipital, the mastoid angle of the parietal, the mastoid part of the temporal, and, just before its termination, the jugular process of the occipital; the portion which occupies the groove on the mastoid part of the temporal is sometimes termed the sigmoid sinus. The<unk>  are frequently of unequal size, with the one formed by the superior sagittal sinus being the larger; they increase in size as they proceed, from back to center. On<unk>  section, the horizontal portion exhibits a prismatic form, the curved portion has a semicylindrical form. They receive the blood from the superior petrosal<unk>  at the base of the petrous portion of the temporal bone; they communicate with the veins of the pericranium by means of the mastoid and condyloid emissary veins; and they receive some of the inferior cerebral and inferior cerebellar veins, and some veins from the diploë. The petrosquamous sinus, when present, runs backward along the junction of the squama and petrous portion of the temporal, and opens into the<unk>  sinus.
Transverse sinuses
Superior sagittal sinus
Inferior sagittal sinus
Canine fossa
Collateral fissure
Suboccipital triangle
Rhomboid fossa
Optic recess