It is triangular in section. It is narrower anteriorly, and gradually increases in size as it passes posterior-ward. It commences at the
foramen cecum, through which it receives
emissary veins from the nasal cavity. It passes posterior-ward along its entire course. It is accommodated within a groove which runs across the inner surface of the
frontal bone, the adjacent margins of the two
parietal lobes, and the superior division of the cruciate eminence of the
occipital lobe. Near the
internal occipital protuberance, it deviates to either side (usually the right) before draining into the
confluence of sinuses, continuing as the corresponding
transverse sinus. Its inner surface presents the openings of the
superior cerebral veins, which run, for the most part, obliquely forward, and open chiefly at the back part of the sinus, their orifices being concealed by fibrous folds; numerous fibrous bands (chordae Willisii) extend transversely across the inferior angle of the sinus; and, lastly, small openings communicate with irregularly shaped venous spaces (venous lacunae, also called 'lateral lacunae' or 'lacunae laterales') in the dura mater near the sinus.
Venous lacunae There are usually three lacunae on either side of the sinus: a small frontal, a large parietal, and an occipital, intermediate in size between the other two. Most of the cerebral veins from the outer surface of the hemisphere open into these lacunæ, and numerous arachnoid granulations (Pacchionian bodies) project into them from below.
Tributaries The superior sagittal sinus receives the
superior cerebral veins, veins from the
diploë and
dura mater, and, near the posterior extremity of the sagittal suture, veins from the
pericranium, which pass through the
parietal foramina. ==Function==