32 OSTEOLOGY, OR ANATOMY OF OSSEOUS SYSTEM 



It is made up of five portions, a body, two greater and two 

 lesser cornua. 



The body is prismatic, presenting three roughly quadrilateral 

 surfaces and five borders. It is compressed obliquely from 

 above downward and backward. 



The superior surface looks upward and a little forward, and 

 is separated by a horizontal border or ridge, with a tubercle 

 in the centre, from the anterior surface. There are depressions 

 above and below this border, on either side of the median line, 

 for muscular attachment of the geniohyoid over the greater 

 part of the anterior surface and adjoining part of the superior. 

 On the superior surface behind this is the geniohyoglossus and 

 chondroglossus. On the anterior surface from within out, the 

 mylohyoid, stylohyoid, and aponeurosis of the digastric, and 

 between two angular processes of the geniohyoid externally, a 

 part of the hyoglossus. 



The posterior surface is concave and faces the epiglottis, 

 from which it is separated by loose areolar tissue and the 

 thyrohyoid membrane. 



The borders are anterior, posterior, and inferior. 



The anterior bonier is rounded and separates the anterior and 

 superior surfaces. The attachment of the geniohyoid extends 

 over much of it. 



The posterior border is well marked and gives attachment 

 to the thyrohyoid membrane. 



The inferior border has attached in front the sternohyoid, 

 and laterally the omohyoid and a part of the thyrohyoid. 



The lateral borders are small and oval for articulation with 

 the greater cornua. 



The great cornua project backward, and are flattened obliquely 

 from above downward, terminating posteriorly in a tubercle 

 for attachment of the lateral thyrohyoid ligament. 



The anteroexternal surface has attached a portion of the 

 hyoglossus, and to the upper border the middle constrictor 

 of the pharynx, and their lower borders a portion of the thyro- 

 hyoid muscle. After middle life they have bony union with 

 the body. 



The .s-//m// conuia are short and conical, and project up and 

 back from the junctions of the great cornua and body; they 

 give attachment to the stylohyoid ligaments and have synnvial 

 articulations with the body. 



