216 Anatomy of Skeleton 



The glenoid fossa is the deep hollow that lies in front of the bony outer meatus. 

 It is crossed by the Glaserian fissure, and can be divided into a mandibular or articular 

 part in front of this fissure, and made by the squama, and a posterior or non-articular 

 part composed of the tympanic plate. The articular part is the deepest portion of the 

 whole fossa, concave in all directions and longer from side to side : its long axis, however, 

 is not quite transverse, but slightly oblique. It is bounded in front by the eminentia 

 articularis, which forms the anterior root of the zygoma and is convex from before 

 backwards and very slightly concave from side to side : the articular surface is carried 

 forward with its cartilaginous lining on to the eminence, for the play of the meniscus 

 in the joint, and thin capsular fibres are attached round the articular surface. The 

 nerve to the Masseter runs out under the anterior margin of the eminence in contact 

 with the anterior capsular fibres * (see Fig. 182). 



The posterior part of the glenoid fossa, formed by the tympanic plate, extends 

 inwards and backwards to reach the styloid process and the situation of the carotid 

 sheath : it is concave in all directions, the bony plate looking forwards, downwards 

 and outwards, and contains some nbro-fatty tissue, or some upper lobules of the 

 parotid if that gland is large. 



The Glaserian fissure is double in its inner part owing to the appearance in it of 

 the edge of the tegmen tympani : in this part between the tegmen and the tympanic 

 plate, the fissure contains the process gracilis of the malleus (with its inferior Meckelian 

 ligament), and affords passage to the chorda tympani and the tympanic branch of the 

 internal maxillary artery. The canal of exit of the nerve, termed sometimes the canal 

 of Huguier, is near the inner end of the fissure and practically marks the spot where 

 Meckel's cartilage lay before its disappearance (see Fig. 172). 



The external auditory meatus is a bony canal running inwards and very slightly 

 forwards, about three-fifths of an inch long, and continuous with the tympanic cavity 

 in the dry bone, but separated from it really by the membrana tympani. The opening 

 and canal are oval on section with the long axis nearly vertical. Its front and lower 

 walls are formed by the tympanic plate, its back wall by this plate fused with the 

 mastoid downgrowth of the squama, and its roof by the lower surface of the squama. 

 The cartilaginous pinna is fastened round the margins of the orifice. 



The squamous part of the bone makes with its lower surface the roof of the meatus, 

 the articular cavity, and the articular eminence : these have been already examined. 

 Above these it forms a thin bony plate that is seen on the side of the skull. The con- 

 cave cerebral surface of this plate is .marked by cerebral gyri, crossed by grooves for 

 middle meningeal vessels, and ends below by turning in to meet the petrous at the petro- 

 squamous suture. 



The outer surface, slightly convex where it helps to form the temporal fossa, is 

 smooth fot origiri\of Temporal muscle fibres : this part is separated below and behind 

 by the p0sterior or ascending root of the zygoma from a slightly concave part of the 

 squama drawnjaown on the mastoid process (Fig. 175) . 



The zygffmatic process springs from the lower part of the outer surface of the 

 squama : it has upper and lower borders and articulates at its extremity, which is 

 serrated, with the malar. The inner surface is smooth and lies on the Temporal muscle, 

 and is continuous behind with the outer surface of the squama by a widened and 

 obliquely-sloped area over which the posterior margin of the Temporal tendon plays. 

 The Masseter arises from its lower border and by muscular fibres from its inner surface. 

 The process has a broad basis of attachment to the squama, which exhibits three 



* For description of joint, see under " Lower Jaw." 



