408 



DIGESTIVE SYSTEM OF THE HORSE 



guttural pouches. From the Eustachian opening a fold of the mucous membrane 

 (Plica salpingo-pharyngea) passes toward but does not reach the aditus laryngis. 

 A horizontal fold, the posterior pillar of the soft palate (Arcus pharyngo-palatinus), 

 passes along the ventral part of the lateral wall and unites with its fellow over the 

 entrance to the oesophagus. The dorsal part of the cavity (Pars respiratoria) 

 is lined with a ciliated epithelium, while the ventral part (Pars digestoria) has a 

 stratified squamous epithelium. The communication between the two is oval 



Hyo - glossy s '^" oTTto -"^ 





Fig. 349. — Posterior Part of a Sagittal Section of Head and Part of Neck op Horse, Cut about 1 cm. to the 



Left of the Medlvn Plane. 

 1, Posterior nares; 3, pharyngeal orifice of Eustachian tube; 3, aditus laryngis; 4^ aditus cesophagi; o, posterior 

 pillar of soft palate; a', junction of S with its fellow over entrance to cesophagus; 6, epiglottis; 7, body of thyroid 

 cartiJage; S, arytenoid cartilage; 9, 9, cricoid cartilage; 10, true vocal cord; 11, false vocal cord; 12, lateral ventricle 

 of larynx; 13, crico-arj^enoideus dorsalis; l^, cesophagus; 15, external carotid artery; 16, hypoglossal nerve; 17, 

 glosso-pharyngeal nerve; .Z5, great cornu of hyoid bone; i5, Eustachian tube; ^0, body of hyoid bone; ^i, hyoideus 

 transversus; 22, ridges of hard palate; 22', soft palate; 23, septum between frontal sinuses; 24-, olfactory mucous 

 membrane; 25, sphenoidal sinus; 26, basilar part of occipital bone; 20', supra-occipital; 27, body of sphenoid bone; 

 2S, pituitarj'- body; 29, chiasma opticum; 30, corpora quadrigemina ; 31, thalamus; 32, arachnoid; 33, odontoid 

 ligament; 34, posterior auricular muacles. 



and is bounded by the free edge of the soft palate and its posterior pillars; it is 

 termed the pharyngeal isthmus. On either side of the aditus laryngis is a narrow 

 deep depression, the piriform recess (Recessus piriformis). 



The submucous tissue contains numerous mucous glands (GlandulEe pharyn- 

 ge£e). In the young subject the lymph follicles are numerous and form a collection 

 dorsally and between the Eustachian openings, known as the pharyngeal tonsil 

 (Tonsilla pharyngea). 



