THE LARYNX 407 



General Construction and Position. The larynx con- 

 stitutes the upper expanded portion of the air-passage which is 

 specially modified for the production of the voice. Its walls 

 are composed of cartilages, muscles, ligaments, and an in- 

 ternal lining of mucous membrane. Before proceeding with 

 the dissection the student should study the form and con- 

 nections of the nine laryngeal cartilages in a permanent speci- 

 men (v. p. 422). 



The larynx is placed in the upper and anterior part of 

 the neck, where it forms a marked projection. It lies below 

 the hyoid bone and tongue, and is directly continuous with 

 the trachea inferiorly. Anteriorly it is covered by the 

 integument and fasciae, and, on either side of the median 

 plane, by two thin strata of muscles viz., the sterno-hyoid and 

 omo-hyoid ; the sterno-thyreoid and the thyreo-hyoid. As a 

 general rule a narrow process of the thyreoid gland, termed 

 the pyramidal lobe, is also continued upwards on its anterior 

 surface. On each side the lateral lobe of the thyreoid gland is 

 prolonged upwards upon it ; and it is related to the great 

 vessels of the neck. Posteriorly it is in relation to the pharynx, 

 which separates it from the prevertebral muscles. If the 

 tip of the epiglottis is taken as its upper limit, the larynx in 

 the adult may be regarded as being placed anterior to that 

 portion of the vertebral column which extends from the lower 

 border of the second to the lower border of the sixth cervical 

 vertebra ; but its position alters somewhat with the movements 

 of the head and also during deglutition. 



Interior of the Larynx. The cavity of the larynx is 

 smaller than might be expected from an inspection of its 

 exterior. On looking into its interior from above it will be 

 seen to be subdivided into three portions by two elevated 

 folds of mucous membrane which extend antero-posteriorly, 

 and project inwards from each side of the cavity. The upper 

 folds are termed \)t\. plicce ventricitlares (O.T. false vocal cords) \ 

 the lower pair receive the name of the plica vocales (O.T. 

 true vocal cords). The latter are the chief agents in the 

 production of the voice, and the larynx is so constructed 

 that changes in their relative position and in their degree of 

 tension are brought about by the action of the muscles and 

 the recoil of the elastic ligaments. 



Vestibulum Laryngis. The vestibule is the upper sub- 

 division of the laryngeal cavity (Fig. 150) ; it extends from the 



