322 HEAD AND NECK 



THE LARYNX. 



The portions of the mandible which are still attached, 

 by mucous membrane, to the sides of the tongue, should 

 be removed, and the dissection of the larynx should be 

 commenced. 



General Construction and Position. The larynx is the 

 upper expanded portion of the wind-pipe which is specially 

 modified for the production of the voice. Its walls are 

 composed of cartilages, muscles, ligaments and membranes, 

 and it has an internal lining of mucous membrane. Before 

 proceeding with the dissection the student should study the 

 form and connections of the nine laryngeal cartilages in a 

 permanent specimen (v. p. 338). 



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 skin 

 and fascise, and, on each 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. Frequently a 

 narrow process of the thyreoid gland, termed the pyramidal 

 lobe^ is continued upwards on its anterior surface. On each 

 side a lobe of the thyreoid gland is prolonged upwards upon 

 it, deep to the muscles ; 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 the position is not fixed : it varies with the 

 movements of the head, and also during deglutition and 

 phonation. 



Interior of the Larynx. The cavity of the larynx is 

 smaller than might be expected from an inspection of its 

 exterior. When its interior is examined 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 

 pair of folds are termed the plica ventriculares (O.T. false vocal 

 cords] ; the lower pair receive the name of the plica vocales 



