ba ere 
766 THE VASCULAR SYSTEM. go BN is 
far as the lower border of the external pterygoid muscle. It les between the 
spheno-mandibular ligament and the neck of the jaw, along with the auriculo- 
temporal nerve and the internal maxillary vein. The second part is in the zygo- 
matic fossa, and ascends upwards and forwards. It may le superficial to, or under 
cover 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 third division of 
the fifth nerve. The third part passes between the upper and the lower heads 
of the external pterygoid, through the pterygo-maxillary fissure and into the 
spheno-maxillary fossa. 
Branches.—/vrom the first part.—(a) Deep auricular (a. auricularis profunda), a 
small branch which rises in the parotid gland and passes upwards to enter the external 
auditory meatus. It supplies the temporo-mandibular joint, the parotid gland, and the 
external meatus, and anastomoses with branches of the superficial temporal and posterior 
auricular arteries. 
(6) The tympanic (a. tympanica anterior), a variable and small branch which com- 
mences in the parotid gland. It runs upwards and backwards, traverses the Glasserian 
fissure, and enters the tympanum through its outer wall. In the tympanic cavity it 
anastomoses with tympanic branches from the internal carotid and the ascending 
pharyngeal arteries, and with the stylo-mastoid branch of the posterior auricular, forming 
with the latter, in young subjects, a circular anastomosis round the tympanic membrane. 
(c) Middle Meningeal (a. meningea media).—The largest branch of the internal 
maxillary. It ascends between the external pterygoid muscle and the spheno-mandibular 
ligament, and passes between the two roots of the auriculo-temporal nerve and through 
the foramen spinosum, to enter the middle fossa of the cranial cavity. Before it enters 
the skull it lies behind the third division of the fifth nerve, and is accompanied by 
two venze comites which also pass through the foramen spinosum. In the middle cranial 
fossa it passes forward and upwards for a short distance, in a groove on the great wing of 
the sphenoid, between the dura mater and the bone, and divides into anterior and 
posterior terminal branches 
Branches.—(i.) Petrosal (ramus petrosus superficialis)—A small branch which arises from the 
middle meningeal soon after it enters the cranium. It passes through the hiatus Fallopii and 
anastomoses with the stylo-mastoid branch of the posterior auricular artery ; it also sends some 
small branches into the tympanic cavity. 
(ii.) Gasserian.—Minute branches which supply the Gasserian ganglion and the roots of the 
fifth cranial nerve. 
(iii.) Tympanic (a. tympanica superior).—A small twig which reaches the tympanic cavity 
through the canal for the tensor tympani muscle, or through the petro-squamous suture. 
(iv.) Orbital. An anastomosing branch which occasionally arises from the anterior terminal 
branch. It passes through the foramen lacerum anterius into the orbit, and anastomoses with the 
lachrymal artery. 
(v.) Anterior terminal, the larger of the two terminal branches, passes upwards along the 
great wing of the sphenoid to the antero-inferior angle of the parietal bone, where it is sometimes 
enclosed in a distinct bony canal; it is continued upwards a short distance behind the anterior 
border of the parietal bone almost to the vertex of the skull, sending branches forwards into the 
anterior, and backwards towards the posterior cranial fossa. 
(vi.) The posterior terminal branch passes backwards from the great wing of the sphenoid to 
the squamous part of the temporal bone, beyond which it ascends to the middle of the inner 
surface of the parietal bone. It sends branches upwards to the vertex, and backwards towards 
the posterior cranial fossa. 
By means of its various branches the middle meningeal artery anastomoses with its fellow of 
the opposite side, with meningeal branches from the occipital, ascending pharyngeal, ophthalmic, 
and lachrymal arteries ; also with the stylo-mastoid branch of the posterior auricular, the small 
meningeal artery, with the deep temporal arteries through the substance of the temporal bone, 
and with its fellow of the opposite side. 
(7) A small meningeal branch (ramus meningeus accessorius) may arise either 
directly from the first part of the internal maxillary or from its middle meningeal branch. 
It passes upwards, on the inner side of the external pterygoid muscle, enters the middle 
fossa of the skull through the foramen ovale, supplies the Gasserian ganglion and the 
dura mater, and terminates by anastomosing with branches of the middle meningeal 
artery. 
(ec) The inferior dental (a. alveolaris inferior) is a branch of moderate size which 
passes downwards between the spheno-mandibular ligament and the mandible to the 
mandibular foramen. It is accompanied by the inferior dental nerve which lies in front. 
aul 
7. 
