IBEANCHES OF THE INTEENAL CAEOTID AETEEY. 903 



scle ; turning upwards and medially, it crosses, between the optic nerve and 

 the superior rectus, to the medial wall of the orbit, where it turns forwards 

 to terminate at the anterior boundary of the cavity by dividing into frontal 

 and dorsal nasal branches. It is accompanied, at first, by the naso-ciliary nerve, 

 and, in the terminal part of its course, by the infra-trochlear nerve. 



Branches. The brandies of the ophthalmic artery are numerous, (a) The posterior ciliary, 

 usually six to eight in number, run forwards at the sides of the optic nerve ; they soon divide 

 into numerous branches which pierce the posterior part of the sclera ; the, majority terminate 

 in the chorioid coat of the eye as the short posterior ciliary arteries, but two of larger size, 

 the long posterior ciliary arteries, run forwards, one on each side of the eyeball, almost in 

 the horizontal plane, between the sclera and the chorioid coat, to the periphery of the iris, 

 where they divide. The resulting branches anastomose together and form a circle at the periphery 

 if the iris, from which secondary branches run inwards and anastomose together in a second 

 circle near the papillary margin of the iris. 



(6) The central artery of the retina arises near to, or in common with, the preceding vessels. 

 It pierces the infero-medial aspect of the optic nerve, about 12 mm. (half an inch) posterior 

 to the sclera, and runs in its centre to the retina, where it breaks up into terminal branches. 



(c) Anterior meningeal. A small branch which passes backwards through the superior orbital 



Ascending parietal artery Ascending frontal arteries 



Inferior lateral 

 frontal artery 



Lateral orbital artery 



Parieto-temporal artery Temporal branches of middle cerebral 



FIG. 763. DISTRIBUTION OF CEREBRAL ARTERIES ON THE CONVEX SURFACE OF THE CEREBRUM. 

 Anterior cerebral artery is coloured green, the middle cerebral red, and the posterior cerebral orange. 



fissure into the middle fossa of the cranium, where it anastomoses with the middle and accessory 

 meningeal arteries, and with the meningeal branches of the internal carotid and lacrimal arteries. 



(d) The lacrimal artery arises from the ophthalmic on the lateral side of the optic nerve. 

 It runs forwards, along the upper border of the lateral rectus, to the upper lateral angle of the 

 orbit, and in its course gives off glandular branches to the lacrimal gland, muscular branches to 

 the lateral and superior recti, palpebral branches to the upper eyelid and the upper and lateral 

 part of the forehead, temporal and zygomatic branches, which accompany the zygomatico-temporal 

 and zygomatico- facial branches of the zygomatic (temporo-malar) nerve, to the face and the 

 infra -temporal fossa respectively ; anterior ciliary branches, which perforate the sclera behind 

 the corneo-scleral junction and anastomose with the posterior ciliary arteries ; and a recurrent 

 meningeal branch, which passes backwards, through the lateral part of the superior orbital 

 fissure, to anastomose, in the middle fossa of the skull, with the middle meningeal artery. 



() Muscular. These branches are usually arranged in two sets, lateral and medial. The 

 former supply the upper and lateral, and the latter the lower and medial orbital muscles. They 

 anastomose with muscular branches from the lacrimal and the supra-orbital vessels, and they 

 give off anterior ciliary branches. 



(/) The supra-orbital branch is given off as the ophthalmic artery crosses above the optic 

 nerve. It passes round the medial borders of the superior rectus and levator palpebrse muscles, 

 and rims forwards, between the levator and the periosteum, to the supra-orbital notch, accompany- 

 ing the frontal nerve and its supra-orbital branch. Passing through the notch it reaches the scalp, 

 and, after it has perforated the frontalis muscle, it anastomoses with the frontal branches of the 

 superficial temporal and ophthalmic arteries. 



(g) Anterior and posterior ethmoidal branches arise from the ophthalmic as it runs forwards 

 along the medial boundary of the orbit. They pass medially, between the superior oblique and 

 the medial rectus. The posterior, which is much the smaller of the two, traverses the posterior 

 ethmoidal canal, and supplies the posterior ethmoidal cells and the posterior and upper part of 



