898 THE VASCULAE SYSTEM. 



median line, with its fellow of the opposite side. It supplies the skin and fascia, and the 

 anterior and superior muscles of the auricle. 



(8) Arteria Maxillaris Interna. The internal maxillary artery commences 

 between the antero-medial surface of the parotid gland and the neck of the 

 mandible, and terminates in the pterygo-palatine fossa. 



Course and Relations. Although the internal maxillary artery is only a 

 short trunk it has many important relations, in the consideration of which it is 

 convenient to divide the vessel into three parts. The first part extends from the 

 back of the neck of the mandible into the infratemporal fossa, as far as the lower 

 border of the external pterygoid muscle. It lies between the spheno-mandibular 

 ligament and the neck of the mandible, along with the auriculo-temporal nerve 

 and the internal maxillary vein. The second part is in the infratemporal fossa, 

 and runs upwards and anteriorly. It may lie on the lateral or the medial side of 

 the lower head of the external pterygoid muscle. In the former case it is situated 

 between the temporal and external pterygoid muscles, and in the latter between 

 the external pterygoid muscle and the branches of the mandibular division of 

 the trigeminal nerve. The third part passes between the upper and the lower 

 heads of the external pterygoid, and through the pterygo-maxillary fissure into 

 the pterygo-palatine fossa. 



Branches. From the first part. (a) Deep auricular. A small branch which arises 

 from the commencement of the artery and passes upwards to the external acoustic 

 meatus. It supplies the mandibular joint, the parotid gland, the external acoustic 

 meatus, and the superficial surface of the tympanic membrane. It anastomoses with 

 branches of the superficial temporal and posterior auricular arteries. 



(b) The anterior tympanic, a variable and small branch. It runs upwards and 

 posteriorly, traverses the petro-tympanic fissure (Glaserian), and enters the tympanum 

 through its lateral wall. In the tympanic cavity it anastomoses with tympanic branches 

 from the internal carotid and ascending pharyngeal arteries, and with the stylo-mastoid 

 branch of the posterior auricular, forming with the latter, in young subjects, a circular 

 anastomosis around the tympanic membrane. 



(c) Middle Meningeal. The largest branch of the internal maxillary. It ascends 

 between the external pterygoid muscle laterally and the spheno-mandibular ligament and 

 the tensor veli palatini medially ; passes between the two roots of the auriculo-temporal 

 nerve and through the foramen spinosum, and enters the middle fossa of the cranial 

 cavity. Before it enters the skull it lies posterior to the third division of the trigeminal 

 nerve, and is accompanied by a vein which also passes through the foramen spinosum. Ir 

 the middle cranial fossa it passes for a short distance anteriorly, in a groove on the greal 

 wing of the sphenoid, between the dura mater and the bone, and divides into anterior anc 

 posterior terminal branches. 



Branches. (i.) Superficial Petrosal. A small branch which arises from the middle meningea 

 soon after it enters the cranium. It passes through the hiatus canalis facialis and anastomose 

 with the stylo-mastoid branch of the posterior auricular artery ; it also sends some small branche 

 into the tympanic cavity. 



(ii.) G-anglionic. Minute branches which supply the semilunar ganglion and the roots of th 

 fifth cerebral nerve. 



(iii.) Superior Tympanic. A small twig which reaches the tympanic cavity through th 

 canal for the tensor tympani muscle, or through the petro-squamous suture. 



(iv.) Orbital An anastomosing branch which arises, occasionally, from the anterior termina 

 branch. It passes through the superior orbital fissure into the orbit, and anastomoses with th 

 lacrimal artery. 



(v.) Anterior terminal, the larger of the two terminal branches, passes upwards along th 

 great wing of the sphenoid to the sphenoidal angle of the parietal bone, where it is sometime 

 enclosed in a distinct bony canal ; it is continued upwards, a short distance behind the anteric 

 border of the parietal bone, almost to the vertex of the skull, sending branches forwards into th 

 anterior, and backwards towards the posterior cranial fossa. 



(vi.) The posterior terminal branch passes posteriorly from the great wing of the sphenoid 1 

 the squamous part of the temporal bone, beyond which it ascends to the middle of the inn< 

 surface of the parietal bone. It sends branches upwards to the vertex, and backwards to wan 

 the posterior cranial fossa. 



By means of its various branches the middle meningeal artery anastomoses with its fellow < 

 the opposite side, with meningeal branches from the occipital, ascending pharyngeal, ophthalmi 

 and lacrimal arteries ; also with the stylo-mastoid branch of the posterior auricular, through tl 

 substance of the temporal bone, with the accessory meningeal artery, and the deep tempor 



