(a) 
(c) 
THE HEAD AND NECK. 251 
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 orbital 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. dentalis 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. pterygopalatina) 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. 
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 eaters 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. 
The fourth cranial, or trochlear nerve (n. trochlearis), is 
distributed to the obliquus superior muscle. 
