The Head and Xeck. 251 



(a) The internal maxillary artery enters the orbit through the 

 anterior sphenoidal foramen in the root of the lateral lamina 

 of the pterygoid process. At the posterior ventral angle of 

 the orbit it gives off the inferior ophthalmic artery 

 (a. ophthalmica inferior). This vessel passes upward and 

 forward on the medial wall of the orbit, giving branches to 

 the eye muscles. It divides into two branches, the frontal 

 artery, which leaves the orbit through the anterior foramen 

 of the supraorbital process, and the lacrimal artery, which 

 passes through the corresponding posterior foramen. The 

 ethmoidal artery, a small branch of the frontal, passes 

 through the minute ethmoidal foramen of the orbical portion 

 of the frontal into the nasal cavity. 



The internal maxillary artery passes forward along the 

 ventral boundary of the orbit, and at the opening of the 

 infraorbital canal gives off a branch, the pterygopalatine 

 artery, continuing as the infraorbital artery. A small 

 branch, the superior dental artery (a. den talis superior) is 

 given off laterally to the alveoli of the upper teeth. 



The infraorbital artery (a. infraorbitalis) passes through 

 the infraorbital canal to the face. 



The pterygopalatine artery (a. pterygopalatine) divides 

 almost immediately into the anterior palatine artery, 

 which traverses the pterygopalatine canal to the mucous 

 membrane of the hard palate, and the sphenopalatine 

 artery, which enters the nasal cavity by the sphenopalatine 

 foramen. 



(b) The divisions of the third cranial, or oculomotor nerve, 



supply the eye muscles, with the exception of the obliquus 



superior, rectus lateralis, and retractor oculi. 



This nerve enters the orbit from the superior orbital fissure in 

 company with certain parts of the trigeminal (e,f). The small nerves 

 passing through the middle and posterior sphenoidal formina of the 

 pterygoid process are the pterygobuccinator and masseterico- 

 temporal nerves, branches of the mandibular, passing to the muscles 

 of mastication. 



(c) The fourth cranial, or trochlear nerve (n. trochlearis), is 

 distributed to the obliquus superior muscle. 



