THE PHAKYNX. 1147 



Relations of the Tonsil. The lateral relations of the tonsil consist of the fibrous capsule 

 and the superior constrictor muscle. Lateral to the pharyngeal wall lies the internal pterygoid 

 muscle, and behind it a region filled with connective tissue, containing blood-vessels and nerves. 



The nearest and most important vessel is the external maxillary artery, which, especially 

 if tortuous, has a very close relation to the pharyngeal wall at this level. 



The ascending palatine and tonsillar branches of the artery are also in close relation. 



The internal carotid artery and internal jugular vein lie considerably further back (f to 1 

 inch) and to the lateral side, and the external carotid artery is still more lateral. 



The ascending pharyngeal artery is well behind the tonsil. 



The size of the palatine tonsils is extremely variable, but as a rule, in early 

 life, they measure something under 1 inch (20 to 22 mm.) from above downwards, 

 about f inch (18 to 20 mm.) antero-posteriorly, and J inch (12 to 15 mm.) medio- 

 laterally. 



The arteries of the palatine tonsil are derived from the ascending palatine and tonsillar 

 branches of the external maxillary artery, the ascending pharyngeal branch of the external 

 carotid, and the dorsalis linguae of the lingual. The veins pass to the tonsillar plexus, on the 

 lateral side of the tonsil, which is an offshoot of the pharyngeal venous plexus. 



Nerves. The palatine tonsil receives a special branch from the glosso-pharyngeal ; this unites 

 with branches from the pharyngeal plexus to form a small plexus tonsillaris which supplies the 

 organ. 



The lymph vessels are extremely numerous. They begin in a plexus which surrounds each 

 follicle, whence vessels pass to the lateral surface of the tonsil. Thence they pass through the 

 wall of the pharynx, and pass to the deep cervical glands in the neighbourhood of the greater 

 cornu of the hyoid bone, behind and inferior to the angle of the mandible. 



Structure of the Palatine Tonsils. Each palatine tonsil is composed of masses of small rounded 

 lymph cells with a delicate connective tissue reticulum. These resemble in structure the folli- 

 culi linguales, q.v. . . 



Upon its medial surface it is covered with epithelium, continuous with the epithelium cover- 

 ing the adjacent parts of the wall of the pharynx. This surface is very irregular, and on section 

 crypts, termed fossulae tonsillares, are seen to be formed by deep infoldings of the epithelial 

 wall. On its lateral surface, the lymph tissue is invested by a connective tissue capsule. 



Pars Laryngea. The laryngeal part of the pharyngeal cavity lies posterior to 

 the larynx (Fig. 903). It is wide above, where it is continuous with the oral portion, 

 and maintains a considerable width until within about an inch of its termination, 

 where, posterior to the cricoid cartilage it narrows rapidly and passes down to join 

 the oesophagus. Except during the passage of food, the anterior and posterior walls 

 of this latter part are in contact, and its cavity is reduced to a mere transverse slit 

 (Fig. 906). 



The anterior wall of the laryngeal portion of the pharynx is formed in its whole 

 extent by the posterior surface of the larynx, of which the following parts are seen 

 from the pharyngeal cavity (Fig. 901): The epiglottis above; below this the 

 superior aperture of the larynx, bounded at the sides by the ary-epiglottic folds ; 

 lateral to these folds is seen, on each side, a deep recess, the recessus piriformis 

 (Fig. 905). Lower down still, the muscles and mucous membrane which cover the 

 posterior surfaces of the arytenoid and cricoid cartilages are distinguishable. 



Its posterior wall and side walls are directly continuous with the corresponding 

 walls of the oral portion, and present no features which require special notice. 



The recessus piriformis (O.T. sinus pyriformis) is a deep depression, seen on each 

 side between the ary-epiglottic fold and the lamina of the thyreoid cartilage. When 

 viewed from above, as in laryngoscopic examinations, it appears of a piriform 

 shape, the wider end being directed upwards and forwards. When viewed from 

 behind, the recess is boat-shaped and elongated in the vertical direction. Its side 

 , wall is formed by the thyreoid cartilage and thyreo-hyoid membrane, covered with 

 mucous membrane ; its medial wall is formed by the ary-epiglottic fold, and slightly, 

 below, by the superior part of the cricoid cartilage. 



Relations of the Pharynx. In considering the relations of the pharynx, it is 

 afc once evident that these are very different in the superior and inferior portions. 



1. Throughout its whole extent it lies anterior to the cervical region of the 

 vertebral column, and is separated from the bodies 'of the vertebrse and the inter- 

 , vertebral fibro-cartilages by the loose areolar tissue of the prevertebral or retro- 

 pharyngeal space, posterior to which lie the anterior longitudinal ligament of the 

 vertebral column, and the longus capitis and longus colli muscles. 



