506 



THE BLOOD-VASCULAR SYSTEM. 



The lachrymal is one of the largest branches derived from the ophthalmic, 

 arising close to the optic foramen ; not infrequently it is given off from the artery 

 before it enters the orbit. It accompanies the lachrymal nerve along the upper 

 border of the External rectus muscle, and is distributed to the lachrymal gland. 

 Its terminal branches, escaping from the gland, are distributed to the eyelids and 

 conjunctiva: of those supplying the eyelids, two are of considerable size and are 

 named the external palpebral ; they run inward in the upper and lower lids 



Nasal. Palpebral. 



h x Frontal. Supra-orbital. 



Anterior ethmoidal. 



Posterior ethmoidal. 



Muscular. 



Temporal branches 

 of lachrymal. 



centralis retinae. 

 Lachrymal. 



Ophthalmic- 



-Internal carotid. 



FIG. 290. The ophthalmic artery and its branches, the roof of the orbit having been removed. 



respectively, and anastomose with the internal palpebral arteries, forming an 

 arterial circle in this situation. The lachrymal artery gives off one or two malar 

 branches, one of which passes through a foramen in the malar bone, to reach the 

 temporal fossa, and anastomoses with the deep temporal arteries ; the other appears 

 on the cheek through the malar foramen, and anastomoses with the transverse 

 facial. A branch is also sent backward through the sphenoidal fissure to the dura 

 mater, which anastomoses with a branch of the middle meningeal artery. 



Peculiarities. The lachrymal artery is sometimes derived from one of the anterior branches 

 of the middle meningeal artery. 



The supra-orbital artery arises from the ophthalmic as that vessel is crossing 

 over the optic nerve. Ascending so as to arise above all the muscles of the orbit, 

 it passes forward, with the supra-orbital nerve, between the periosteum and 

 Levator palpebrse; and, passing through the supra-orbital foramen, divides into a 

 superficial and deep branch, which supply the integument, the muscles, and the 

 pericranium of the forehead, anastomosing with the frontal, the anterior branch 

 of the temporal, and the artery of the opposite side. This artery in the orbit 

 supplies the Superior rectus and the Levator palpebree, and sends a branch 

 inward, across the pulley of the Superior oblique muscle, to supply the parts at the 

 inner canthus. At the supra-orbital foramen it frequently transmits a branch to 

 the diploe. 



The ethmoidal branches are two in number posterior and anterior. The 



