154 



NORMAL HISTOLOGY. 



Muscular 

 fibres 



The pharyngeal tonsil is an unpaired median mass of lymphoid 

 tissue in the postero-superior wall of the naso-pharynx. It, as well as the 

 faucial tonsils, is best developed in early childhood ; when hypertrophied, it 



constitutes "adenoids." This tonsil 

 consists of a series of lobulated 

 masses of lymphoid tissue arranged 

 around a central depression with 

 lateral recesses. In its general 

 composition, it resembles the faucial 

 tonsil, consisting of lymph-nodules 

 and diffuse lymphoid tissue. The 

 latter is less circumscribed and infil- 

 trates the surrounding mucous mem- 

 brane, so that the limits of the 

 pharyngeal tonsil are not well defined. 

 The name, tubal tonsils, is some- 

 times applied to the collections of 

 lymphoid tissue that surround the 

 openings of the Eustachian tubes. 

 The lymphoid tract extends for some 

 distance along the tube, as well as 

 towards the pharyngeal tonsil, and 

 contains small lymph-nodules. 



The blood-vessels and nerves 

 of the pharynx, although collectively 

 derived from a varied and somewhat 

 complex source, follow in their 

 detailed distribution the plan com- 

 mon to mucous membranes, and call 

 for no special description. 



FIG. 193. Section through faucial tonsil, showing The lymphatics within the 



c5J5? x S 2o silion f lymphoid tissue around the pharyngeal mucous membrane are 



unusually abundant, particularly in 



the vicinity of the more definite masses of lymphoid tissue. The latter, espe- 

 cially the faucial tonsils, are of great practical importance. They are very 

 frequently the seat of serious infections, their numerous and often deep crypts 

 affording favorable resting places for bacteria. 



THE CESOPHAGUS. 



The oesophagus or gullet is the tube, about 25 cm. in length, that 

 connects the pharynx and the stomach and serves for the passage of food. 

 Its walls, 3-4 mm. thick, consist of four coats (Fig. 194) which, from within 

 outwards, are: (i) the mucous membrane, (2) the submucous layer, (3) the 

 muscular tunic and (4) the fibrous coat. 



The mucous membrane, usually thrown into longitudinal folds, 

 includes a tunica propria, composed of fibrous connective tissue and delicate 

 elastic fibres, and a thick coating of stratified squamous epithelium. The 

 surface of the stroma-layer beneath the epithelium is modelled by longitudi- 

 nal ridges and papillae, between which pass the ducts of the glands in their 

 course to the free surface. The deeper part of the tunica propria is occupied 

 by a thin stratum of involuntary muscle, the muscularis mucosa, which is 

 feeble and indistinct in the upper part of the gullet but robust and conspic- 



