548 THE BLOOD-VASCULAR SYSTEM 



distance in a groove on the greater wing of the sphenoid, and then divides into two branches, an 

 anterior and a posterior. 



The anterior branch passes upward, in the groove on the greater wing of the sphenoid, on 

 to the parietal bone at its anterior and inferior angle; at this spot the groove becomes deepened 

 and often bridged over by a thin plate of bone, being converted for 6 to 12 mm. (^ to 5 in.) or 

 more into a distinct canal. The situation of the artery is here indicated on the exterior of the 

 skull by a spot 3.7 cm. (1| in.) behind, and about 2.5 cm. (1 in.) above, the zygomatic process 

 of the frontal bone. The anterior branch is continued along the anterior border of the parietal 

 bone nearly as far as the superior sagittal sinus, and gives off in its course, but especially poste- 

 riorly, large branches which ramify in an upward and backward direction in grooves on the pari- 

 etal bone (fig. 452). 



The posterior branch passes backward over the squamous portion of the temporal bone; 

 and thence on to the parietal bone, behind the anterior branch. This branch and its collaterals 

 extend upward as far as the sagittal sinus, and backward as far as the transverse (lateral) 

 sinus. 



In addition to its terminal anterior, and terminal posterior branches, the middle meningeal 

 gives off: — (a) Ganglionic branhecs to the semilunar (Gasserian) ganglion and its sheath of 

 dura mater. (6) A superficial petrosal branch [ramus petrosus superficialis], which enters 

 the hiatus of the facial canal in company with the large superficial petrosal nerve and anasto- 

 moses with the terminal branch of the stylo-mastoid artery, (c) A superior tympanic artery 

 [a. tympanica superior], which enters the canal for the tensor tympani, and supplies that muscle. 

 (d) An orbital or lacrimal branch, which enters the orbit at the outermost part of the superior 

 orbital (sphenoidal) fissure, or sometimes through a minute foramen, just lateral to that 

 fissure, and anastomoses with the lacrimal branch of the ophthalmic, (e) Anastomotic or 

 perforating branches which pierce the greater wing of the sphenoid bone, and anastomose with 

 the deep temporal arteries. 



(4) The inferior alveolar artery [a. alveolaris inferior] (fig. 451), arising from the internal 

 maxillary as it lies between the spheno-mandibular ligament and neck of the jaw, courses 

 downward to the mandibular foramen, which it enters in company with, and a little behind 

 and lateral to, the inferior alveolar nerve. It then passes along the canal in the interior of the 

 bone, giving off branches to the molar, premolar, and canine teeth. On reaching the mental 

 foramen it divides into two branches, the incisive and the mental. The incisive continues its 

 course in the bone, supplies branches to the incisor teeth, and anastomoses with the artery of 

 the opposite side. The mental branch [ramus mentalis] passes through the mental foramen in 

 company with the mental branch of the inferior alveolar (dental) nerve, and emerges on the chin 

 under cover of the quadratus labii inferioris. It anastomoses above with the inferior labial 

 (coronary), and below with the submental, and also with the inferior labial. Near its origin 

 the artery gives off (a) a lingual or gustatory branch, which accompanies and supplies the lingual 

 nerve, and ends in the mucous membrane of the mouth; and, just before it enters the man- 

 dibular (dental) foramen in the lower jaw, (6) a mylo-hyoidean branch [ramus mylohyoideus], 

 which accompanies the nerve of that name along the groove in the lower jaw, and, after supply- 

 ing the mylo-hyoid muscle, anastomoses with the sublingual and submental arteries. 



(5) The accessory or small meningeal branch [ramus meningeus accessoria] arises either 

 from the internal maxillary a little in front of the middle meningeal, or as a branch of the latter 

 vessel. It passes upward along the course of the mandibular division of the fifth nerve, and, 

 entering the skull through the foramen ovale, is distributed to the semilunar (Gasserian) 

 ganglion, and to the walls of the cavernous sinus and the dura mater in the neighbourhood. 



Branches of the Second Part of the Internal Maxillary Artery 



The branches of the second portion of the internal maxillary all supply muscles. They 

 are: — (1) The ma.sseteric; (2) the posterior deep temporal; (3) the pterygoid; (4) the buccal; 

 and (5) the anterior deep temporal. 



[(1) The masseteric artery [a. masseterica] comes off from the internal maxillary as the latter 

 is pa.ssing from Ix'tween tlie neck of the jaw and the spheno-mandibular ligament. It passes, 

 with the masseteric nerve through the mandil)ular (sigmoid) notch in the mandible and supplies 

 the massotor muscle. Some filaments jxTf orate the muscle and anastomose with tlie transverse 

 facial and witli tlie nuLssctcric branches of the external maxillary (facial). 



(2) The posterior deep temporal artery [a. temporalis profunda i)osterior] arises, as a rule, 

 from the inleriial maxillary in common with the ma.sseteric for a little beyond that branch. 

 It pas.se H uj)ward beneath the temimrnl nniscle in a slight groove on the anterior margin of 

 the squamous portion of the temporal bone, sui)})Iying tlio temporal nuiscle, the pericranium 

 and the extern;! I layer of the bone. It anastomoses with the other temporal arteries. 



(3) The pterygoid branches [rami pterygoidei] are short trunks which i)ass into and supply 

 the interri;il and (jxteriial i)terygoid muscles. 



(4) T]\(' buccal artery [a. buccinatoria] (fig. 451) courses forward and downward with the 

 buccal nerve to the l)uccinator muscle, lying in close contact with the n)edial side and anterior 

 margin of the U'lulow of tlie tf'ni[)oral muscle and coronoid i)rocess of the lower jaw. It supplies 

 the buccitiat(jr muscle and mucous membrane of the mouth, and anastomo.ses with the external 

 maxillary (fM-\;d), tr;insvcrse f;icial, and infraorbital arteries. 



(5j The anterior deep temporal artery [a. temporalis profunda anterior] ascends beneath the 

 temi)oral muscle in a slight groove on the greater wing of the splienoid bone. It supplies the 

 muscle, pericranium, and subjacent bone, and gives off small branches which pass through 

 minute foramina in the zygomatic (malar) bone. Some of these last branches enter the orbit 

 and ariastorno.se with the lacrimal artery; others emerge on the face and anastomose with the 

 transverse facial artery. 



