THE LARYNX 



329 



Crico-thyreoid ligament 



fibres, and cord-like right and left margins, the lateral thyreo- 

 hyoid ligaments, whilst in the intervals between the central 

 part and the lateral margins it is thin and weak. The median 

 ligament is attached, above, to the posterior aspect of the 

 upper margin of the body of the hyoid bone ; below, it is fixed 

 to the sides of the deep median notch on the upper border of 

 the thyreoid cartilage. The upper part of its anterior surface, 

 therefore, lies behind the hollowed-out posterior surface of 

 the body of the hyoid bone ; a mucous bursa is interposed 

 between them, and in certain movements of the head and 

 larynx the upper border 

 of the thyreoid cartilage 

 is allowed to slip up- 

 wards behind the hyoid 

 bone. On each side of 

 the strong central part, 

 the thy reo- hyoid mem- 

 brane is attached, below, 

 to the upper margin of 

 the lamina of the thyreoid 

 cartilage, and, above, to 

 the deep aspect of the 

 greater cornu of the 

 hyoid bone. It is pierced 

 by the internal laryngeal 

 nerve and superior laryn- 

 geal vessels. The lateral 



FIG. 122. The Crico-thyreoid Muscle. 



thyreo - hyoid ligament, 

 which forms the pos- 

 terior border of the membrane, on each side, is rounded and 

 cord-like, and is composed chiefly of elastic fibres. It extends 

 from the tip of the greater cornu of the hyoid bone to the 

 extremity of superior cornu of the thyreoid cartilage. In it 

 there is usually developed a small, oval cartilaginous or bony 

 nodule, termed the cartilago triticea (Fig. 127). 



Musculus Crico-thyreoideus. Each crico-thyreoid muscle 

 is placed on the corresponding side of the cricoid cartilage, 

 and bridges over the lateral portion of the crico-thyreoid 

 interval. It takes origin from the lower border and outer 

 surface of the arch of the cricoid cartilage, whence its fibres 

 spread out in an upward and backward direction, and are 

 inserted into the inner aspect of the lower margin of the 



