A MANUAL OF ANATOMY 



wards. The anterior surface is convex, and is crossed transversely 

 by a ridge, which divides it into an upper and a lower part. At 

 the middle line this is intersected at right angles by a vertical 

 ridge, which, however, is often incomplete, being sometimes con- 

 fined to the upper half, and sometimes to the lower. At the place 

 of intersection of the two ridges there is a slight projection, called 

 the hyoid tubercle. Each half of the anterior surface is thus mapped 

 out into an upper and a lower irregular muscular division. The 

 upper division, provided the uppsr border is not very thick, gives 

 attachment to the genio-hyoid and genio-hyo-glossus, and the 

 lower division to the digastric, stylo-hyoid, and mylo-hyoid. The 

 posterior surface is concave, and is covered by the thyro-hyoid 

 membrane as it ascends to be attached to the superior border, a 

 synovial bursa intervening. This surface is related to the epiglottis. 



Great Cornu ■- 



Small Cornu 



Body _ 



—"-Middle 

 Constrictor 



— -"ilyo-glossus 



" ■ Chondro-glossiLs 



-- Genio-hyo-glossus 

 - Digastric 

 Stylo-hyoid 



Omo-hyoid (Ant. Belly) 



Thyro-hyoid 

 . Mylo-hyoid 



I Sterno-hyoid 



Genio-hyoid 



Fig. yy. — The Hyoid Bone, showing its Muscui,ar Attachments. 



The superior border is somewhat thick, and occasionally is really a 

 surface, in which cases it gives attachment to the genio-hyo- 

 glossus, whilst its posterior lip gives attachment to the thyro-hyoid 

 membrane. The inferior border is sharp, and gives insertion to the 

 sterno-hyoid, anterior belly of the omo-hyoid, and thyro-hyoid 

 muscles. Each lateral border is connected with a great cornu. 



The great cornua project upwards and backwards from the lateral 

 borders of the body. Each is compressed from above downwards, 

 and gradually diminishes in size to its termination, where it ends 

 in a small tubercle for the attachment of the thyro-hyoid ligament. 

 It gives attachment to fibres of the thyro-hyoid, hyo-glossus, middle 

 constrictor muscle of the pharynx, and the thyro-hyoid membrane. 

 Each great cornu is connected with the body by synchondrosis 

 up to middle life, after which ankylosis usually takes place. 



