MUSCLES OF THE LARYNX. 529 



and the front of the epiglottis. The folds of mucous mem- 

 brane connecting the epiglottis to the base of the tongue, 

 have also been called ligaments they are three in num- 

 ber. The middle one, called the frenum epiglottidis , has a 

 few elastic fibres and some cellular tissue. 



Muscles of the Larynx. The muscles of the larynx are 

 nine in number, eight of which are in pairs. 



Dissection. Make the same in- FIG. 162. 



cisions as for the anterior neck, 

 and remove the platysma, fascia, 

 and sterno-hyoideus, and sterno- 

 thyroideus muscles. We thus ex- 

 pose the anterior muscles of the 

 larynx which are the thyro-hy- 

 bideus and crico-thyroideus. 



The tliyro-liyoideus (Fig. 162) is 

 a broad, flat muscle, and looks very 

 much like a continuation of the 

 sterno-thyroideus. It arises from 

 the oblique line on the ala of the 

 thyroid cartilage, ascends, and is in- a ' 

 serted into the lower margin of the 

 corrm of the os-hyoides and part 

 of its base. Its function is to raise 

 the larynx, or when the latter is 

 fixed to draw down the os-hyoides. 



The crico-thyroideus (Fig. 162) 

 is a short muscle, lying below the last. It arises from the 

 anterior surface of the cricoid cartilage; its fibres pass 

 outward and upward, to be inserted into the inferior mar- 

 gin arid cornu of the thyroid. 



function. To bring these two cartilages towards each 

 other, and thus shorten the vocal case. 



On the lateral and posterior portions of the larynx we 

 have the tliyro~arytenoideus,,crico-arytenoideus posticus, crico- 

 arytenoideus lateralis, arytenoideus obliquus, arytenoideus 



FIG. 162 represents the Muscles in front of the Larynx, a Sterno thy- 

 roideus. 6 Crico-thyroideus. c Thyro-hyoideus. d Mylo-h\oideus. 



31 



