1278 



A MANUAL OF ANATOMY 



following structures : (i) the thyro-epiglottidean ligament, (2) the 

 superior thyro-arytenoid ligaments (false vocal cords), and (3) the 

 inferior thyro-arytenoid ligaments (true vocal cords), in association 

 with which are the fibres of the thyro-arytenoid muscles. 



Isthmus (Pomum Adami) 



Cricoid Cartilage 



Superior Cornu of Thyroid 

 Cartilage 



.. Superior Tubercle of Ala 

 . .Oblique Line of Ala 



Inferior Cornu 



«^Crico-thyroid Ligament 



Inferior Tubercle of Ala 



Fig. 526 — The Thyroid and Cricoid Cartilages of the Larynx 

 (Lateral View). 



Arytenoid Facet 



Development of the Thyroid Cartilage. — The thyroid cartilage is regarded 

 as being developed from the ventral portions of the skeletal cartilages of the 

 fourth and fifth visceral arches of either side, which become united by a 

 median plate. 



Cricoid Cartilage. — The cricoid cartilage is situated below the 

 thyroid cartilage, and forms the lower part of the larynx. It bears 

 some resemblance to a signet-ring, and it 

 consists of two parts — an anterior arch and a 

 posterior lamina. 



The anterior arch is narrow from above 

 downwards as well as from side to side. The 

 inferior border is horizontal, and is connected 

 with the first ring of the trachea by a fibro- 

 elastic membrane. The superior border is con- 

 nected with the inferior border of thyroid 

 cartilage by the median portion of the crico- 

 thyroid membrane. 



The posterior lamina is quadrilateral and 

 broad. It attains considerable depth, owing to 

 the rapid elevation of the superior border of 

 the anterior arch as it passes backwards. The 

 inferior border is connected laterally with the first ring of the 

 trachea by a fibro-elastic membrane, and mesially, where the 

 tracheal rings are deficient, to the same membrane. The superior 

 border presents a median notch, and on either side of this an oval 



Posterior Surface 



Fig. 527.— The Cri- 

 coid Cartilage of 

 the Larynx (Pos- 

 terior View). 



