THE HYOID BONE. 



123 



Body. 



YLO-HYOID. 

 OMO-HYOIO. 



OENIO-HYOID. 



STERNO-HYOID. 



MYLO-HYOID. 



aponeurosis of the Digastric (suprahyoid aponeurosis) ; and between these to part 

 of the Hyo-glossus. The posterior surface is smooth, concave, directed backward 

 and downward, and separated from 

 the epiglottis by the thyro-hyoid 

 membrane and by a quantity of 

 loose areolar tissue. The superior 

 border is rounded, and gives at- 

 tachment to the thyro-hyoid mem- 

 brane, part of theGenio-hyo-glossi 

 and Chondro-glossi muscles. The 

 inferior border gives attachment, 

 in front, to the Sterno-hyoid; 

 behind, to the Omo-hyoid and to 

 part of the Thyro-hyoid at its 

 junction Avith the great cornu. 

 It also gives attachment to the 



Levatore glandulaB thyroideae when FIG. 78.-Hyoid bone. Anterior surface. (Enlarged.) 



this muscle is present. The lat- 

 eral surfaces after middle life are joined to the greater cornua. In early life they 

 are connected to the cornua by cartilaginous surfaces, and held together by liga- 

 ments, and occasionally a synovial membrane is found between them. 



The Greater Cornua (thyro-hyaT) project backward from the lateral surfaces of 

 the body ; they are flattened from above downward, diminish in size from before 

 backward, and terminate posteriorly in a tubercle for the attachment of the lateral 

 thyro-hyoid ligament. The outer surface gives attachment to the Hyo-glossus, 

 their upper border to the Middle constrictor of the pharynx, their lower border to 

 part of the Thyro-hyoid muscle. 



The Lesser Cornua (cerato-hyals] are two small, conical-shaped eminences 

 attached by their bases to the angles of junction between the body and greater 

 cornua, and giving attachment by their apices to the stylo-hyoid ligaments. 1 

 The smaller cornua are connected to the body of the bone by a distinct diar- 

 throdial joint, which usually persists throughout life, but occasionally becomes 

 ankylosed. 



Development. By five centres : one for the body, and one for each cornu. 

 Ossification commences in the body about the eighth month, and in the greater 

 cornua toward the end of foetal life. Ossification of the lesser cornua commences 

 some years after birth. Sometimes there are two centres for the body. 



Attachment of Muscles. Sterno-hyoid, Thyro-hyoid, Omo-hyoid, aponeurosis 

 of the Digastric, Stylo-hyoid, Mylo-hyoid, Genio-hyoid, Genio-hyo-glossus, Chon- 

 dro-glossus, Hyo-glossus, Middle constrictor of the pharynx, and occasionally 

 a few fibres of the Inferior lingualis. It also gives attachment to the thyro- 

 hyoidean membrane and the stylo-hyoid, thyro-hyoid, and hyo-epiglottic liga- 

 ments. 



Surface Form. The hyoid bone can be felt in the receding angle below the chin, and the 

 finger can be carried along the whole length of the bone to the greater cornu, which is situated 

 just below the angle of the jaw. This process of bone is best perceived by making pressure on 

 one cornu, and so pushing the bone over to the opposite side, when the cornu of this side will 

 be distinctly felt immediately beneath the skin. This process of bone is an important landmark 

 in ligature of the lingual artery. 



Surgical Anatomy. The hyoid bone is occasionally fractured, generally from direct vio- 

 lence, as in the act of garrotting or throttling. The great cornu is the part of the bone most fre- 

 quently broken, but sometimes the fracture takes place through the body of the bone. In con- 

 sequence of the muscles of the tongue having important connections with this bone, there is 

 great pain upon any attempt being made to move the tongue, as in speaking or swallowing. 



1 These ligaments in many animals are distinct bones, and in man are occasionally ossified to a 

 certain extent. 



