NERVES 143 



In sinus communicates with cavernous plexus and third, 

 fourth, and sixth nerves, and divides into three branches, 

 two of which, frontal and lachrymal, enter orbit above 

 external rectus, whilst the third or nasal passes between two 

 heads of origin of that muscle, and between two divisions of 

 3rd nerve. 



Branches : 



Lachrymal : passes along outer wall of orbit to under sur- 

 face of lachrymal gland, communicates with orbital of 

 superior maxillary, finally pierces palpebral fascia, and sup- 

 plies skin of upper eyelid, inosculating with branches of facial. 



Frontal : largest branch, enters orbit just outside 4th nerve, 

 passes forward on levator palpebrae, and divides into : 



Supra -trochlear : directed forwards and inwards between 

 pulley and supra-orbital notch ; distributed to forehead and 

 communicates with infra-trochlear. 



Supra-orbital : continuation of frontal, passes through notch, 

 supplies palpebral filaments, and ends on forehead by dividing 

 just outside orbit into two branches, of which the external is 

 the larger. It supplies the scalp. Communicates with facial. 



Nasal : enters orbit between the heads of the external 

 rectus, passes forwards and inwards over optic nerve along 

 inner side of orbit, through anterior ethmoidal foramen ; 

 re-entering cranium, it passes down nasal slit by the side of 

 the crista galli, dividing into two terminal branches, viz : 



Internal : supplying mucous membrane of the septum. 



External : runs along groove on internal surface of nasal 

 bone, then passes between bone and lateral cartilage to 

 supply skin of ala, and tip of nose. Communicates with 

 facial. 



Branches from nasal in the orbit : 



Ganglionic : arises between heads of external rectus, passes 

 along outer side of optic nerve, entering the posterior superior 

 angle of lenticular ganglion, of which it forms the long or 

 sensory root. 



Long ciliary (2 or 3) pass along inner side of optic nerve, 

 join some short ciliary branches from ganglion, and, piercing 

 sclerotic, are distributed to ciliary body and iris. 



Infra-trochlear : given off as nerve enters anterior ethmoidal 

 foramen ; it passes to inner angle of orbit, communicating 

 beneath ' pulley ' with the supra- trochlear of frontal. It sup- 

 plies lachrymal sac, skin of eyelids and root of nose. 



The LENTICULAR GANGLION is a small reddish-coloured 

 body, placed between the optic nerve and the external rectus, 

 at the back part of the orbit. 



