86 VETERINARY STATE BOARD 



appendages by one of its constituent pieces, the thyroid cartilage. 

 Its anterior opening is at the bottom of the pharynx, its posterior 

 is continuous with the trachea. 



In structure, it is comprised of five cartilages, viz., three single, 

 cricoid, thyroid and epiglottis, and one pair, the arytenoids. The 

 muscles which either move the whole organ or its cartilages upon 

 one another are: three extrinsic, the sternothyroideus, hyothy- 

 roideus and the hyo-epiglottideus; five intrinsic, cricothyroid, pos- 

 terior crico-arytenoideus, lateral crico-arytenoid, thyro-arytenoid 

 and arytenoideus. All of these muscles are pairs, except the hyo- 

 epiglottideus and arytenoideus. 



Internally, the larynx is lined with mucous membrane and is 

 marked on each side by the elastic structure known as the vocal 

 cords. 



Blood supply: laryngeal arteries. 



Nerve supply: superior and inferior laryngeal. 



Function : an air passage and organ of phonation. 



Name the cartilages of the larynx. 



See answer to preceding question. 



Describe the guttural pouch and give its function. 



Two in munber, one on each side, the guttural pouches are elon- 

 gated cavities, communicating with the pharynx and lying on its 

 sides. In reality, a dilatation of the eustachian tube, these two 

 pouches lie against each other in the median plane ; externally, they 

 are related to the carotid artery and parotid gland. Before and 

 behind, they extend from the anterior part of the pharynx to the 

 inferior face of the atlas. Capacity, about three-quarters of a pint. 

 Function : probably connected with hearing and phonation in some 

 way. 



Describe the trachea and give its relations. 



The trachea is a long, flexible, elastic, cylindrical tube, composed 

 of a series of about fifty incomplete cartilaginous rings that succeed 

 the cricoid cartilage of the larynx and terminate above the base of 

 the heart by bifurcating into the two bronchi. The rings are united 

 by fibrous tissue. 



Relations : In its cervical portion, surrounded by muscles of this 

 region — sternohyoid and sternothyroid, in front; the sternomaxil- 

 laris muscles are situated in front in the inferior part but on the 

 sides near their termination; the subscapulohyoideii are placed 

 above and in the middle of the lateral parts; the scaleni are below 

 and at the sides ; the longus colli, behind. The cesophagus descends 



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