Squamous part of the frontal bone

Internal surface

The internal surface of the squamous part is concave and presents in the upper part of the middle line a vertical groove, the sagittal sulcus, the edges of which unite below to form a ridge, the frontal crest; the sulcus lodges the superior sagittal sinus, while its margins and the crest afford attachment to the falx cerebri.

The crest ends below in a small notch which is converted into a foramen, the foramen cecum, by articulation with the ethmoid.

This foramen varies in size in different subjects, and is frequently impervious; when open, it transmits a vein from the nose to the superior sagittal sinus.

On either side of the middle line the bone presents depressions for the convolutions of the brain, and numerous small furrows for the anterior branches of the middle meningeal vessels.

Several small, irregular fossæ may also be seen on either side of the sagittal sulcus, for the reception of the arachnoid granulations.