



THE EXTERIOR OF THE SKULL 183 



The squamosal suture arches backward from the pterion and connects the tem- 

 poral squama with the lower border of the parietal: this suture is continuous 

 behind with the short, nearly horizontal parietomastoid suture, which unites the 

 mastoid process of the temporal with the region of the mastoid angle of the parietal. 

 Extending from above downward and forward across the cranium are the coronal 

 and lambdoidal sutures; the former connects the parietals with the frontal, the latter, 

 the parietals with the occipital. The lambdoidal suture is continuous below with 

 the occipitomastoid suture between the occipital and the mastoid portion of the 

 temporal. In or near the last suture is the mastoid foramen, for the transmission 

 of an emissary vein. The point of meeting of the parietomastoid, occipitomastoid, 

 and lambdoidal sutures is known as the asterion. Immediately above the orbital 

 margin is the superciliary arch, and, at a higher level, the frontal eminence. Near 

 the center of the parietal bone is the parietal eminence. Posteriorly is the ex- 

 ternal occipital protuberance, from which the superior nuchal line may be followed 

 forward to the mastoid process. Arching across the side of the cranium are the 

 temporal lines, which mark the upper limit of the temporal fossa. 



The Temporal Fossa (fossa temporalis}. The temporal fossa is bounded above 

 and behind by the temporal lines, which extend from the zygomatic process of the 

 frontal bone upward and backward across the frontal and parietal bones, and then 

 curve downward and forward to become continuous with the supramastoid crest 

 and the posterior root of the zygomatic arch. The point where the upper temporal 

 line cuts the coronal suture is named the stephanion. The temporal fossa is bounded 

 in front by the frontal and zygomatic bones, and opening on the back of the latter 

 is the zygomaticotemporal foramen. Laterally the fossa is limited by the zygomatic 

 arch, formed by the zygomatic and temporal bones; below, it is separated from the 

 mfratemporal fossa by the infratemporal crest on the great wing of the sphenoid, 

 and by a ridge, continuous with this crest, which is carried backward across the 

 temporal squama to the anterior root of the zygomatic process. In front and 

 1 elow, the fossa communicates with the orbital cavity through the inferior orbital 

 ( r sphenomaxillary fissure. The floor of the fossa is deeply concave in front and 

 convex behind, and is formed by the zygomatic, frontal, parietal, sphenoid, and 

 temporal bones. It is traversed by vascular furrows; one, usually well-marked, runs 

 i ipward above and in front of the external acoustic meatus, and lodges the middle 

 temporal artery. Two others, frequently indistinct, may be observed on the 

 ; nterior part of the floor, and are for the anterior and posterior deep temporal 

 arteries. The temporal fossa contains the Temporalis muscle and its vessels and 

 nerves, together with the zygomaticotemporal nerve. 



The zygomatic arch is formed by the zygomatic process of the temporal and 

 1 he temporal process of the zygomatic, the two being united by an oblique suture ; 

 the tendon of the Temporalis passes medial to the arch to gain insertion into the 

 coronoid process of the mandible. The zygomatic process of the temporal arises 

 by two roots, an anterior, directed inward in front of the mandibular fossa, where 

 it expands to form the articular tubercle, and a posterior, which runs backward 

 above the external acoustic meatus and is continuous with the supramastoid 

 orest. The upper border of the arch gives attachment to the temporal fascia; 

 che lower border and medial surface give origin to the Masseter. 



Below the posterior root of the zygomatic arch is the elliptical orifice of the 

 external acoustic meatus, bounded in front, below, and behind by the tympanic 

 part of the temporal bone; to its outer margin the cartilaginous segment of the 

 external acoustic meatus is attached. The small triangular area between the 

 posterior root of the zygomatic arch and the postero-superior part of the orifice is 

 termed the suprameatal triangle, on the anterior border of which a small spinous 

 process, the suprameatal spine, is sometimes seen. Between the tympanic part 

 and the articular tubercle is the mandibular fossa, divided into two parts by the 



