40 Bones of the Skull. 



Cornu majns 

 Comu minus 



51 and 52. Hyoid bone, os hyoideum. 



From above. Right half, from the left. 



The os hyoideum (hyoid bone} lies as an unpaired, horse -shoe -shaped bone behind 

 and below the lower jaw between the muscles, without direct connection with the other bones. 

 It is divisible into a middle piece or corpus, two cornua majora and two cornua minora. 



The corpus (body) is a transversely placed oblong plate with an anterior surface, bent 

 so as to be convex in front and above, and a concave posterior surface. The anterior surface 

 presents variably developed ridges for the muscular attachments, the posterior is smooth. At 

 the lateral ends are small fossae, below for union with the cornua majora, above for the 

 cornua minora. 



The cornua majora are thin, laterally flattened plates of bone, longer than the body. 

 They are placed horizontally or directed obliquely upward, are united in front with the body 

 by means of a narrow plate of cartilage or by a small joint with a joint cavity and a tight 

 capsule. Behind, each ends in a small button -like projection. 



The cornua minora are small pieces, sometimes remaining cartilaginous, which are 

 attached above near the point of union of the body and the cornua majora, either by means 

 of a small joint with joint cavity and loose capsule or by ligamentous union only. They are 

 surrounded by the end of the ligamentum stylohyoideum (see Fig. 555), a thin round elastic 

 fibrous ligament which extends from the processus styloideus oss. tempor. interwoven in the 

 deep layer of the cervical fascia. Sometimes it contains masses of bone, the single pieces 

 being more or less separated from one another. The processus styloideus, the lig. stylohyoideum 

 and the cornu minus oss. hyoid. arise from the second branchial arch of the foetus. 



