THE LARYNX. 



1105 



The *ni.>i:i'i"i- or false vocal cords, so called because they are not directly 

 concerned in the production of the voice, are two folds of mucous membrane, 

 each enclosing a delicate rounded band, the superior thyro-arytenoid ligament. 

 This ligament consists of areolar tissue, attached in front to the angle of the thy- 

 roid cartilage below the epiglottis, and behind to the antero-external surface of the 

 arytenoid cartilage, just above the fossa triangularis. This ligament, enclosed in 

 mucous membrane, forms a free margin, which constitutes the upper boundary of 

 the corresponding ventricle of the larynx. 



The inferior or true vocal cords, so called from their being concerned in the 

 production of sound, are two strong fibrous bands (inferior ihyro-arytenoid liga- 

 nicut*). covered on their surface by a thin layer of mucous membrane. These 

 ligaments have already been described. Each forms the lower boundary of the 

 corresponding ventricle of the larynx. Externally, the Thyro-arytenoideus (inner 

 portion) muscle lies parallel with it. 



The ventricle of the larynx is an oblong fossa situated between the superior 

 and inferior vocal cords on each side, and extending nearly their entire length. 

 This fossa is bounded above by the free crescentric edge of the superior vocal 

 cord, below bv the straight margin of 



/ O O 



the true vocal cord, externally by the 

 mucous membrane covering the inner 

 surface of the corresponding Thyro-ary- 

 tenoideus muscle (outer portion). The 

 anterior part of the ventricle leads up 

 by a narrow opening into a caecal pouch 

 of mucous membrane of variable size 

 called the laryngeal pouch. 



The saccuhis laryngis, or laryngeal 

 pouch, is a membranous sac placed 

 between the superior vocal cord and 

 the inner surface of the thyroid carti- 

 lage, occasionally extending as far as 

 its upper border ; it is conical in form, 

 and curved slightly backward. On the 

 surface of its mucous membrane are the 

 openings of sixty or seventy small fol- 

 licular glands which are lodged in the 

 sub mucous areolar tissue. This sac is 

 enclosed in a fibrous capsule continuous 

 below with the superior thyro-arytenoid 

 ligament : its laryngeal surface is cov- 

 ered by muscular fibres derived from 

 from those found in the aryteno-epiglot- 

 tic fold (Aryteno-epiglottideus inferior 

 muscle. Compressor sacculi laryngis, 

 Hilton), whilst its exterior is covered by the Thyro-arytenoideus and Thvro-epi- 

 glottideus muscles. 



Muscles. The muscles of the larynx are eight in number, and are as follows : 



The Orieoid-thyroid is triangular *in form, and situated at the fore part and side 

 of the cricoid cartilage. It arises from the front and lateral part of the cricoid 

 cartilage : its fibres diverge, passing obliquely upward and outward to be inserted 

 into the lower border of the thyroid cartilage and into the anterior border of the 

 lower cornua. 



The inner borders of these two muscles are separated in the middle line by a 

 triangular interval occupied by the crico-thyroid membrane. 



The Orico-arytenoideu* posticu* arises from the broad depression occupying 

 each lateral half of the posterior surface of the lamina of the cricoid cartilage ; its 

 fibres pass upward and outward, converging to be inserted into the muscular pro- 

 70 



Vocal cords, 



ventricle - 



between thtm 



Aryteno- 

 piglottic fold. 



Arytenoid 

 cartilage. 



.RYTENCIDCUS 

 MUSCLE. 



Crico-thyroid 

 membrane. ~ 



Trachea. 



FIG. 702. Vertical section of the larynx and upper 

 part of the trachea. 



