THE ZYGOMATIC BONE 



93 



wall and roof of the nasal fossa, and at its medial end touches the ala of the vomer. The 

 lateral surface looks forward and laterally into the pterygo-palatine (spheno-maxillary) fossa. 

 Of the two bordera,the posterior is thin and articulates with the medial pterygoid plate; the 

 anterior border forms the posterior boundary of the spheno-palatine foramen. 



The orbital process is somewhat pyramidal in shape, and presents for examination five 

 surfaces, three of which — the posterior, anterior, and medial — are articular and the rest non- 

 articular. The posterior or sphenoidal surface is small and joins the anterior surface of the 

 body of the sphenoid; the medial or ethmoidal articulates with the labyrinth of the ethmoid; 

 and the anterior or maxillary, which is continuous with the lateral surface of the perpendicular 

 part, is joined with the maxiUa. Of the two non-articular surfaces, the superior or orbital, 

 directed upward and laterally, is slightly concave, and forms the posterior angle of the floor 

 of the orbit; the lateral or zygomatic, smooth and directed lateral, looks into the pterygo- 

 palatine (spheno-maxillary) and zygomatic fossae, and forms the anterior boundary of the 

 spheno-palatine foramen. The process is usually hollow and the cavity completes one of the 

 posterior ethmoidal cells or communicates with the sphenoidal sinus. 



Fig. 117. — Maxilla and Palate Bones show^ing how the Infra-orbital Groove 

 Runs Outward almost at Right Angles from the Neighbourhood of the Spheno- 

 palatine Foramen on the Back of the Maxilla and the Orbital Process of the 

 Palate. Posterior View. (E. Fawcett.) 



Infra-orbital groove 



Between the orbital and sphenoidal processes is the spheno-palatine notch, converted by 

 the body of the sphenoid, into a complete foramen. It leads from the pterygo-palatine fossa 

 into the back part of the nasal cavity close to its roof, and transmits the medial branches from 

 the spheno-palatine ganglion and the spheno-palatine vessels. 



Blood-supply. — The palate bone receives branches from the descending palatine and the 

 spheno-palatine arteries. 



Articulations. — With the sphenoid, maxiUa, vomer, inferior nasal concha, ethmoid, and its 

 fellow of the opposite side. 



Ossification. — The palate is ossified in membrane from a single centre which appears about 

 the eighth week at the angle between the horizontal and perpendicular parts. At birth the 

 two parts are nearly equal in length, but as the nasal fossae increase in vertical depth, the 

 perpendicular part is lengthened until it becomes about twice as long as the horizontal part. 



THE ZYGOMATIC 



The zygomatic [os zygomaticum] or malar bone (fig. 118) forms the promi- 

 nence known as the cheek and joins the zygomatic process of the temporal wdth the 

 maxilla. It is quadrangular in form with the angles directed vertically and 

 horizontally. The malar (or external) surface is convex and presents one or two 

 small orifices for the transmission of the zygomatico-facial nerves and vessels. 

 It is largely covered by the orbicularis oculi and near the middle is slightlj' ele- 

 vated to form the malar tuberosity, which gives origin to the zygomaticus and 

 zygomatic head of quadrate muscle of upper lip. 



The temporal (or internal) surface is concave and looks into the temporal 

 and infratemporal fossae; it is excluded from the orbit by a prominent curved plate 



