INFERIOR MAXILLARY BONE. 



.51 



Fig. 27.* 



lower jaw, which gives attachment by its inner margin to the stylo- 

 maxillary ligament. 



The upper extremity of the ramus presents two processes, separated 

 by a concave sweep, the sigmoid notch. The anterior is the coronoid 

 process; it is sharp and 

 pointed, and gives attach- 

 ment by its inner surface 

 to the temporal muscle. The 

 anterior border of the coro- 

 noid process is grooved at 

 its lower part for the buc- 

 cinator muscle. The poste- 

 rior process is the condyle 

 of the lower jaw, which is 

 flattened from before back- 

 wards, oblique in direction, 

 and smooth upon its upper 

 surface, to articulate with 

 the glenoid cavity of the 

 temporal bone. The con- 

 striction around the base of 



the condyle is its neck, into which is inserted the external pterygoid 

 muscle. The sigmoid notch is crossed by the masseteric artery and 

 nerve. 



The internal surface of the ramus is marked near its centre by a 

 large oblique foramen, the inferior dental, for the entrance of the 

 inferior dental artery and nerve into the dental canal. Bounding this 

 opening is a sharp margin, to which is attached the internal lateral 

 ligament, and passing downwards from the opening a narrow groove 

 which lodges the mylo-hyoidean nerve with a small artery and vein. 

 To the uneven surface above, and in front of the inferior dental fora- 

 men, is attached the temporal muscle, and to that below it the internal 

 pterygoid. The internal surface of the neck of the condyle gives at- 

 tachment to the external pterygoid muscle ; and the angle to the 

 stylo-maxillary ligament. 



Development. By two centres ; one for each lateral half, the two 

 sides meeting at the symphysis, where they become united. The 

 lower jaw is the earliest of the bones of the skeleton to exhibit ossifi- 

 cation, with the exception of the clavicle ; ossific union of the sym- 

 physis takes place during the first year. 



* The lower jaw. l. The body. 2. The ramus. 3. The symphysis. 4. 

 The fossa for the depressor labii inferioris muscle. 5. The mental foramen. 

 6. The external oblique ridge. 7- The groove for the facial artery ; the situa- 

 tion of the groove is marked by a notch in the bone a little in front of the num- 

 ber. 8. The angle. 9- The extremity of the mylo-hyoidean ridge. 10. The 

 coronoid process. 11. The condyle. 12. The sigmoid notch. 13. The inferior 

 dental foramen. 14. The mylo-hyoidean groove. 15. The alveolar process. 

 i. The middle and lateral incisor tooth of one side. c. The canine tooth, h. 

 The two bicuspides. m. The three molares. 



