910 THE RESPIRATORY SYSTEM. 
broader. The inferior border of the cricoid is nearly horizontal, although it~ 
frequently presents a median projection in front, and a lateral projection on 
either side. It is joined to the first ring of the trachea by an intervening elastic 
membrane. On the owter surface of the cricoid cartilage, at the place where the 
anterior arch joins the posterior lamina, a vertical ridge descends from the 
arytenoid articular facet. On this, a short distance from the lower border of the 
cartilage, a prominent circular articular facet is visible for articulation with the 
inferior cornu of the thyroid cartilage (Fig. 615, p. 915). The inner surface of 
the cricoid cartilage is smooth, and is lined by mucous membrane. 
The narrow band-like part of the anterior arch of the cricoid cartilage lies 
below the lower border of the thyroid cartilage, whilst the posterior lamina is — 
received into the interval between the posterior portions of the ale of the thyroid 
cartilage. 
Arytenoid Cartilages (cartilagines aryteenoide ).—The arytenoid cartilages are 
placed one on either side of the mesial plane, and rest upon the upper border of the 
— posterior lamina of the cricoid 
a=) cartilage, in the interval between 
Hyoid bone the posterior portions of the als of 
? the thyroid cartilage. They pre- 
sent a somewhat pyramidal form. 
The pointed apex or summit of each 
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EPIGLOTETIS 
Bye s 
ee eas B _! _ Cartilago triticea 
: Y Thyro-epiglottidean : . E : j B 
“Uy isan oe is directed upwards, and at the same 
y Sunerion conten time curves backwards and inwards. 
Y thyroid cartilage It supports the corniculum laryngis. 
Of the three surfaces, one looks 
directly inwards towards the cor- 
responding surface of the opposite 
Cartilage of Santorini Cartilage, from which it is separated 
Arytenoid cartilage by a narrow interval; another looks 
arvignaid eartitgs, backwards; whilst the third sj 
directed outwards and _ forwards. 
ag The internal surface, which is the 
eee ecaliee smallest of the three, is triangular 
in outline. It is narrow, vertical, — 
and even, and is clothed by the 
lining mucous membrane of the 
larynx. The posterior surface 18 
smooth and concave from above 
downwards; it lodges and gives 
attachment to the arytenoideus— 
transversus muscle. The antero- 
Fic. 614.—CaRTILAGES AND LIGAMENTS OF LARYNX, external surface is the most exten- : 
as seen from behind. ‘ i : } 
sive of the three. Its middle part — 
is marked by a deep depression in which is lodged a mass of mucous glands. — 
Upon this surface of the arytenoid cartilage the powerful thyro-arytenoid muscle 
is inserted, whilst a small tubercle a short distance above the base gives attach-_ 
ment to the superior thyro-arytenoid ligament—the feeble supporting ligament 
of the false vocal cord. The three surfaces of the arytenoid cartilage are” 
separated from each other by an anterior, a posterior, and an external border. 
The external border is the longest, and it pursues, as it is traced from the apex to 
the base, a sinuous course. Reaching the base of the cartilage, it is prolonged 
outwards and backwards in the form of a stout prominent angle or process, termed 
the processus muscularis. Into the front of this process is inserted the crico 
arytenoideus lateralis muscle; whilst into its posterior aspect the crico-arytenoideus — 
posticus muscle is inserted. A small nodule of yellow elastic cartilage, called” 
the sesamoid cartilage, is frequently found on the external border of the arytenoid 
cartilage, where it is held in position by the investing perichondrium. The 
anterior border of the arytenoid is vertical, and at the base of the cartilage 1s 
prolonged horizontally forwards into a sharp-pointed process called the processus 
