DISSECTION OF THE LARYNX. 



SnrrroN XVI. 





THE HYOID BONE, THE CARTILAGES AND LIGAMENTS OP 

 THE LARYNX. AND THE STRUCTURE OF THE TRACHEA. 



Dissection. 



Hyoid bone : 

 form ; 



body; 



cornua, 

 large 



and small. 



In larynx 

 there are 

 four large 



and some 

 small carti- 



Thyroid 



Dissection. A fresh larynx should be obtained for this Section 

 if possible. Failing that good use may be made of the parts 

 remaining in the specimen already examined. All the muscles am 

 the mucous membrane are to be taken away so as to denude th< 

 hyoid bone, the cartilages of the larynx, and the epiglottis ; but tht 

 membrane joining the hyoid bone to the thyroid cartilage, and tl 

 ligaments uniting one cartilage to another on the left side, shoul< 

 not be destroyed. 



In the aryteno-epiglottidean fold of mucous membrane, a sim 

 cartilaginous body (cuneiform) may be recognised ; an oblique 

 whitish projection indicates its position. 



The HYOID BONE (fig. 248) is situate between the larynx and th( 

 root of the tongue. Resembling the letter U placed horizontally, 

 and with the. legs turned backwards, it offers for examination a centre 

 part or body, and two lateral pieces or cornua on each side. 



The body (G) is elongated transversely, in which direction it 

 measures about an inch, and flattened from before backwards. 

 The anterior surface is convex, and marked in the centre by 

 a tubercle, on each side of which is an impression for muscular 

 attachment. The posterior surface is concave and smooth. To 

 the upper border the hyo-glossal membrane, fixing the tongue, is 

 attached. 



The cornua are two in number on each side large and small. 

 The large cornu (H) continues the bone backwards, and is joined to 

 the body by an intervening piece of cartilage, or in old persons by 

 continuous bony union. The surfaces of this cornu look rather 

 upwards and downwards ; and the size decreases from before back- 

 wards. It ends posteriorly in a tubercle. The small cornu (j) is 

 directed upwards from the point of union of the great cornu with 

 the body, and is joined by the stylo-hyoid ligament ; it is seldom 

 wholly ossified. It is united to the body of the bone by a synovial 

 joint, with a surrounding capsule. 



CARTILAGES OP THE LARYNX (fig. 248). There are four large 

 cartilages in the larynx, by which the vocal cords are supported, 

 vi/., the thyroid, the cricoid, and the two arytenoid. In addition 

 there are some yellow fibro-cartilaginous structures, viz., the epi- 

 glottis, a capitulum to each arytenoid cartilage, and a small ovalish 

 piece (cuneiform) in each aryteno-epiglottidean fold of mucous 

 membrane. 



The THYROID CARTILAGE (B) is the largest of all : it forms the 

 Iront of the larynx, and protects the vocal apparatus as with a 

 shield. The upper part of the cartilage is considerably wider than 



