748 



HUMAN ANATOMY. 



out inward, avoiding the internal jugular vein, the pneumogastric and sympathetic 

 nerves, and the ascending pharyngeal and external carotid arteries. 



The collateral circulation is carried on through the vertebrals and the vessels of 

 the circle of Willis and is freely re-established. 



I. The Tympanic Artery. — The tympanic artery (ramus caroticotympani- 



cus) is a small vessel which arises from the petrosal portion of the internal carotid. 

 It passes through a foramen in the wall of the carotid canal to supply the mucous 

 membrane of the middle ear, anastomosing with the tympanic branches of the stylo- 

 mastoid and internal maxillary arteries. 



Fig. 696. 



Facial artery 



Frontal artery 



Internal branch of 



supraorbital 



Superior oblique muscle ^ 



Superior palpebral 



branch 

 Inferior palpebral 

 branch 

 Frontal artery 



Nasal artery 

 Anterior ethmoidal 

 branch 

 Supraorbital artery 



Posterior ethmoidal 

 branch 



Superior oblique 



Superior rectus 

 Optic nerve, 



Ophthalmic artery 



Internal carotid artery 

 Posterior clinoid process 



Internal carotid, 



cavernous portion 



Nasal artery 



Supraorbital artery 



Levator palpebrae superioris 

 Superior rectus 



Lachrymal artery 



Lachrymal gland 



Temporal branch 



Arteria centralis retinae 

 Long posterior 



ciliary arteries 

 Short posterior 



ciliary arteries 



Middle fossa of skull 



Branches of right ophthalmic artery, seen from above after removal of roof of orbit. 



2. The Anterior Meningeal Arteries. — The anterior meningeal arteries 

 are a number of small branches which arise from the intracranial portion of the inter- 

 nal carotid and are supplied to the neighboring dura mater, anastomosing with the 

 branches of the anterior ramus of the middle meningeal artery. 



3. The Ophthalmic Artery. — The ophthalmic artery (a. ophthalmica) ( Figs. 

 696, 697) arises from the internal carotid immediately after it has issued from the roof 

 of the cavernous sinus. It passes forward beneath the optic nerve and traverses the 

 optic foramen with that structure. In the orbit it ascends to the outer side of the 

 optic nerve and, crossing over it, passes in a sinuous course towards the inner wall 



