658 



ANGIOLOGY 



sinuses 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 diploe. The petrosquamous sinus, when present, runs 

 backward along the junction of the squama and petrous portion of the temporal, 

 and opens into the transverse sinus. 



The occipital sinus (sinus occipitalis) (Fig. 570) is the smallest of the cranial 

 sinuses. It is situated in the attached margin of the falx cerebelli, and is generally 

 single, but occasionally there are two. It commences around the margin of the for- 

 amen magnum by several small venous channels, one of which joins the terminal 

 part of the transverse sinus ; it communicates with the posterior internal vertebral 

 venous plexuses and ends in the confluence of the sinuses. 



The Confluence of the Sinuses (confluens sinuum; torcular Herophili) is the term 

 applied to the dilated extremity of the superior sagittal sinus. It is of irregular 

 form, and is lodged on one side (generally the right) of the internal occipital pro- 

 tuberance. From it the transverse sinus of the same side is derived. It receives 

 also the blood from the occipital sinus, and is connected across the middle line with 

 the commencement of the transverse sinus of the opposite side. 



The antero-inferior group of sinuses comprises the 



Two Cavernous. 

 Two Intercavernous 



Two Superior Petrosal. 

 Two Inferior Petrosal. 



Basilar Plexus. 



The cavernous sinuses (sinus cavernosus) (Figs. 570, 571) are so named because 

 they present a reticulated structure, due to their being traversed by numerous inter- 

 lacing filaments. They are of irregular 

 Internal carotid artery form, larger behind than in front, and 

 Cavernous sinus are placed one on either side of the 

 body of the sphenoid bone, extending 

 from the superior orbital fissure to 

 the apex of the petrous portion of 

 the temporal bone. Each opens be- 

 hind into the petrosal sinuses. On 

 the medial wall of each sinus is the 

 internal carotid artery, accompanied 

 by filaments of the carotid plexus; 

 near the artery is the abducent nerve; 

 on the lateral wall are the oculomotor 

 and trochlear nerves, and the oph- 

 thalmic and maxillary divisions of 

 the trigeminal nerve (Fig. 571). These structures are separated from the blood 

 flowing along the sinus by the lining membrane of the sinus. The cavernous 

 sinus receives the superior ophthalmic vein through the superior orbital fissure, 

 some of the cerebral veins, and also the small sphenoparietal sinus, which courses 

 along the under surface of the small wing of the sphenoid. It communicates with 

 the transverse sinus by means of the superior petrosal sinus; with the internal 

 jugular vein through the inferior petrosal sinus and a plexus of veins on the inter- 

 nal carotid artery ; with the pterygoid venous plexus through the foramen Vesalii, 

 foramen ovale, and foramen lacerum, and with the angular vein through the 

 ophthalmic vein. The two sinuses also communicate with each other by means 

 of the anterior and posterior intercavernous sinuses. 



The ophthalmic veins (Fig. 572), two in number, superior and inferior, are 

 devoid of valves. 



Oculomotor nerve 

 Trochlear nerve 



Ophthalmic nerve 

 Abducent nerve 



Maxillary nerve 



FIG. 571. Oblique section through the cavernous sinus. 



