THE LARYNX. 



961 



Glosso-epiglottic 



yteno- 

 ipiglottic fold. 



Arytenoid 

 cartilage. 



rtNOtocui 



USCLE 



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

 production of sound, are two strong bands (inferior tJiyro-arytenoid ligaments), 

 covered on their surface by a thin layer 

 of mucous membrane. Each ligament 

 consists of a band of yellow elastic tis- 

 sue, attached in front to the depression 

 between the two alse of the thyroid carti- 

 lage, and behind to the anterior angle 

 (vocal process) of the base of the aryte- 

 noid. Its lower border is continuous 

 with the thin lateral part of the crico- 

 thyroid membrane. Its upper border 

 forms the lower boundary of the ven- 

 tricle of the larynx. Externally, the 

 Thyro-arytenoideus muscle lies parallel 

 with it. It is covered internally by 

 mucous membrane, which is extremely 

 thin, and closely adherent to its surface. 



The ventricle of the larynx is an 

 oblong fossa, situated between the supe- 

 rior and inferior vocal cords on each 

 side, and extending nearly their entire 

 length. This fossa is bounded, above, 

 by the free crescentic edge of the supe- 

 rior vocal cord ; below, by the straight 

 margin of the true vocal cord ; exter- 

 nally, by the mucous membrane cover- 

 ing the corresponding Thyro-arytenoid- 

 eus muscle. The anterior part of the 

 ventricle leads up by a narrow opening 

 into a csecal pouch of mucous membrane of variable size, called the laryngeal 

 pouch. 



The sacculus laryngis, or laryngeal pouch, is a membranous sac, placed between 

 the superior vocal cord and the inner surface of the thyroid cartilage, occasionally 

 extending as far as its upper border or even higher : it is conical in form, and 

 curved slightly backward. On the surface of its mucous membrane are the open- 

 ings of sixty or seventy mucous glands, which are lodged in the submucous areolar 

 tissue. This sac is enclosed in a fibrous capsule, continuous below with the superior 

 thyro-arytenoid ligament : its laryngeal surface is covered by the Aryteno-epiglot- 

 tideus inferior muscle (Compressor sacculi laryngis, Hilton) ; while its exterior is 

 covered by the Thyro-arytenoideus and Thyro-epiglottideus muscles. These mus- 

 cles compress the sacculus laryngis, and discharge the secretion it contains upon 

 the chordae vocales, the surfaces of which it is intended to lubricate. 



Muscles. The intrinsic muscles of the larynx are eight in number, five of 

 which are the muscles of the vocal cords and rima glottidis, and three are con- 

 nected with the epiglottis. 



The five muscles of the vocal cords and rima glottidis are the 



Crico-thyroid. Crico-arytenoideus lateralis. 



Crico-arytenoideus posticus. Arytenoideus. 



Thyro-arytenoideus. 



The Crico-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. 



61 



FIG. 530. Vertical section of the larynx and upper 

 part of the trachea. 



