THE PHARYNX 1233 



organ into irregular compartments. Within the compartments is the delicate framework and 

 reticulum in the meshes of which are found diffuse lymphoid tissue and solitary nodules or 

 follicles. The internal surface presents twelve to fifteen depressions or crypts (fossulae tonsil- 

 lares), that extend into the organ in the form of irregular, blindly ending, tortuous channels or 

 follicles. The internal surface of the tonsils and the crypts and follicles are lined by stratified 

 squamous cells, exhibiting in places marked degenerative changes, and in others leukocytes 

 that are passing through the epithelial layer to the crypts. The tonsils seem to present a 

 hilus at the anterior margin just under cover of the anterior pillar of the soft palate, as here the 

 vessels seem to enter and leave. 



The arteries supplying the tonsils are the dorsalis linguae from the lingual, the ascending 

 palatine and tonsillar from the facial, the ascending pharyngeal from the external carotid, , 

 the descending palatine branch of the internal maxillary, and a twig from the small meningeal. 

 The veins terminate in the tonsillar plexus, on the outer side of the tonsil, and the tonsillar 

 plexus joins the pharyngeal plexus, which communicates with the pterygoid plexus of the 

 internal jugular or facial vein. They seem to enter and leave at the hilus. 



Surrounding each follicle is a close plexus of lymphatic vessels. From these plexuses the 

 lymphatic vessels pass to the submaxillary lymph nodes below the angle of the mandible. From 

 the submaxillary nodes lymph passes to the deep cervical nodes. 



The Nerves of the Tonsil. A branch from the glossopharyngeal nerve by uniting with 

 branches of the pharyngeal plexus forms the tonsillar plexus. 



Development. The tonsils are developed from the lower parts of the second visceral clefts, 

 immediately behind the anterior pillars of the fauces. The entoderm which lines these clefts 

 grows in the form of a number of solid buds into the surrounding mesoderm. These buds 

 become hollowed out by the degeneration and casting off of their central cells, and by this means 

 the tonsillar crypts are formed. Lymphoid cells accumulate around the crypts, and become 

 grouped to form the lymphoid follicles; the latter, however, are not well defined until after birth. 



Applied Anatomy. When a tonsil enlarges it projects inward. The deafness which so often 

 attends hypertrophy of the tonsil is not due to blocking of the Eustachian orifice by the tonsil, 

 but is due to thickening of the mucous membrane lining the tube itself. The profuse bleeding 

 which sometimes follows an operation for the removal of the tonsil is very seldom due to injury 

 of the internal carotid artery, but is due to injury of the ascending pharyngeal artery (p. 600) 

 or one of the palatine arteries. 



The Laryngeal Part of the pharynx (pars laryngea pkaryngis) is that division 

 which lies behind the larynx; it is wide above where it is continuous with the oral 

 portion, while below at the lower border of the cricoid cartilage it becomes continu- 

 ous with the resophagus. In front it presents the triangular aperture of the larynx, 

 the base of which is directed forward and is formed by the epiglottis, while its 

 lateral boundaries are constituted by the arytenoepiglottic folds. On either side 

 of the laryngeal orifice is a recess, termed the sinus pyriformis (recessus pyriformis} 

 (Fig. 950); it is bounded internally by the arytenoepiglottic fold, externally by 

 the thyroid cartilage and thyrohyoid membrane. In the anterior part of the sinus 

 pyriformis is a fold (plica nervi laryngei), which passes downward and inward. 

 Extending outward from the epiglottis on each side is a fold, the pharyngoepiglottic 

 fold (plica pharyngoepiglottica). This ascends in the lateral wall of the pharynx, 

 nearly to the posterior arch of the fauces. 



Structure. The pharynx is composed of mucous, fibrous, and muscular coats. 



The mucous coat (tunica mucosa) is continuous with that lining the Eustachian tubes, the 

 nasal fossae, the mouth, and the larynx. In the nasopharynx it is covered by stratified ciliated 

 epithelium; in the buccal and laryngeal portions the epithelium is of the stratified squamous 

 variety. In the tunica propria considerable diffuse lymphoid tissue, pharyngeal, tonsil, and 

 mucous glands (glandulae pharyngeae) are found; the latter are especially numerous at the upper 

 part of the pharynx around the orifices of the Eustachian tubes. 



The pharyngeal aponeurosis or fibrous coat is situated between the mucous and the muscle 

 layers, and consists of large bundles of white fibrous connective tissue. It is thick above, where 

 the muscle fibres are wanting, and is firmly connected to the periosteum of the basilar process of 

 the occipital and petrous portion of the temporal bones. As it descends it diminishes in thick- 

 ness, and is gradually lost. It is strengthened posteriorly by a strong fibrous band, which is 

 attached above to the pharyngeal spine on the under surface of the basilar portion of the occipital 

 bone, and passes downward, forming a median raphe, which gives attachment to the Constrictor 

 muscles of the pharynx. 



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