Orbit and Cavernous Sinus - LO 8
8. Trace the branches of ophthalmic artery and veins. Identify the association of the neurovasculature of the orbit with the cavernous sinuses.
The ophthalmic a. branches from the internal carotid a. after the ICA emerges from the cavernous sinus. The ophthalmic a. enters the orbit through the optic canal and branches to supply the structures of the orbit. The bulk of the ophthalmic a. may be found between the superior oblique m. and the medial rectus m., along the medial border of the orbit, and the many smaller branches typically accompany their namesake V1 branches (e.g. lacrimal, ant./post. ethmoidal, supra-orbital, supratrochlear, etc.). The ophthalmic a. gives rise to the central artery of the retina, which is bundled with the optic n. (CN II).
The central artery of the retina is the first branch of the ophthalmic a. The central artery of the retina enters the dural sheath of the optic n. (CN II) and travels within the nerve to the retina.
The superior ophthalmic v. drains blood from the eye, superior orbit, ethmoidal cells, forehead, and the angular v. of the face. The inferior ophthalmic v. collects blood from the face and inferior orbit. Both the superior and inferior ophthalmic vv. may transport blood from the face to the cavernous sinus.
The cavernous sinuses are relatively expansive dural venous sinuses lateral to the sella turcica, extending between the superior orbital fissures (anteriorly) and the apices of the petrous part of the temporal bones (posteriorly). Tributaries of these sinuses include ophthalmic vv., sphenoparietal sinuses, and superficial middle cerebral vv. The cavernous sinuses drain into the petrosal sinuses. Structures traversing the cavernous sinus include: the internal carotid a., abducens n. (CN VI), and internal carotid plexus of sympathetic nn. The oculomotor (CN III), trochlear (CN IV), and the ophthalmic (V1) and maxillary (V2) divisions of the trigeminal n. (CN V) are located in the lateral walls (meningeal layer of dura mater) of the cavernous sinuses. Cavernous sinus thromboses may endanger these structures.
