Thyroid Cartilage 125 



THE LARYNX 



The larynx is hung from the hyoid bone and the styloid process. 

 It is continuous with the trachea at the level of the lower border of the 

 fifth cervical vertebra. Above and in front is the tongue ; behind is 

 the pharynx, into which it opens by the glottis. 



Standing out in the middle line of the neck, between the two sterno- 

 mastoids, it forms a groove in which lie the common carotid artery with 

 the internal jugular vein and the vagus. 



The thyroid cartilage consists of the alas which unite in a promi- 

 nent angle, thepomum Adami, separated from the fascia and skin by 

 a small bursa. 



On the outer surface of the ala a ridge runs downwards and for- 

 wards from the root of the superior cornu, for the insertion of the 

 sterno-hyoid and the origin of the thyro-hyoid. The inferior con- 

 strictor of the pharynx arises from the surface behind the ridge. The 

 inner surface of the ala is covered by mucous membrane, and, at the 

 retiring angle, gives attachment to the vocal cords and the thyro- 

 arytaenoid muscles. To the upper border is attached the thyro-hyoid 

 membrane. The crico-thyroid muscle and membrane are connected 

 with the lower border. 



The posterior borders of the cartilage are widely separated, the 

 gap being filled in below by the cricoid and arytasnoid cartilages, and 

 they receive the insertion of the stylo-pharyngei. The width of the 

 lower part of the pharynx is maintained by the attachment of the 

 inferior constrictor to the posterior part of the alae. The posterior 

 borders lie close to the front of the middle cervical vertebras, and in 

 roughly pushing' the cartilage across the front of the vertebrae a moist 

 sort of crepitus is produced, which, being first noticed after an injury, 

 might possibly suggest fracture. 



Fracture of the thyroid cartilage may result from violence. There 

 is difficulty and pain in coughing and swallowing, and there are swell- 

 ing and tenderness about the larynx. The patient should be kept on 

 his back and fed on enemata and liquid food; he should not be allowed 

 to talk. Tracheotomy may be needed if the injury and swelling are 

 great. 



The cricoid cartilage, named from its resemblance to a signet- 

 ring (KptKo?), has its expanded part in the gap between the alas of the 

 thyroid, and its slender part in front, below the thyroid, with which it 

 is connected by the crico-thyroid membrane. Its lower border is at- 

 tached to the first ring of the trachea by a thin membrane. From the 

 posterior part arise the crico-arytasnoidei postici and the longitudinal 

 fibres of the oesophagus. The arytaenoid cartilages articulate with 

 the upper part of the expanded portion, and the inferior cornua of the 



