;i7l ////: DIGESTIVE APPARATUS l.\ M.\MM i/./.i. 



internal pttryi.'1'id and stylo-hyoid iiinsc-lt s. tli.- gloBtO-pharyngeal, 

 liyj" -glossal, and superior laryngcal nerves, and ; WOUU :u ' 



STKUCTUBE The walls of tho pharynx are eoiupi- .1 of ;i /,/// 

 bruin; exterual to which is a nuxrufiir layer. 



1. Mucou* mi-ii<l>i-ttiti-. This membrane is covered, externally, by a thin 

 layer of yellow clastic fibres, and is much more delicate and h-s< }>rte<-t<d 

 by its epidermis than the buccal mucous membrane, of which it is u oon 

 tiiiuation; it also communicates with that of tho oesophagus, the larynx, the 

 nasal fossae, and the Eustnchian tubes. 



Its epithelium is stratified throughout; but it is thin and rilinti-il in the 

 upper part, thicker and tesselated on the inferior moiety, which more 

 particularly belongs to the digestive apparatus. 



Everywhere there are racemose glands, though they are most nunu Tons 

 towards tho roof of tho pharynx. There are also some foUinilfir <jl<m<l* 

 beneath the mucous membrane, in the neighbourhood of the guttural opening, 

 the misal cavities, and the Eustachiau tubes. 



2. Muscular layer. This is composed of seven pairs of muscles, indicated 

 in the following enumeration: the palato pharyngeus, pterygo-pha /// 

 hyo-pJiarynijeus, thyro-pharyngeus, crico-pharyngeus, aryteno-pharyngeus, stylo- 

 pharyngeua. 



PALATO-PHARYNGEUS (Pliaryngo-stapliylinus). This muscle, which has 

 already been described as belonging to tho soft palate, is prolonged back- 

 wards on the lateral wall of the pharynx, where its fibres are mixed with 

 those of the pterygo-pharyngeus, and go to be attached to the superior 

 border of the thyroid cartilage by passing beneath tho hyo-pharyngeal 

 and thyro-pharyngeal muscles. It therefore also belongs to the pharynx. 



PTEUYGO-PHAUYNGEUS, OB SUPEUIOU CONSTKICTOR (the palato pliariin<j< //xof 

 fiiU). This muscle is thin, wide, flat, and triangular. It originates 

 from tho pterygoid process, whence its fibres diverge, some posteriorly, 

 others inwardly. The former mix with those of the palato-pharyngeus, 

 and comport themselves like that muscle ; and tho latter are united, on 

 the median line, with the analogous fibres of tho opposite muscle, form- 

 ing a kind of zone around the origin of the Eustachian ttibc. This 

 muscle is covered, externally, by a layer of yellow clastic tissue, which is 

 attached with it to tho pterygoid bone ; afterwards it is fixed to the superior 

 border of the great branch of the os hyoides, and is even prolonged on tho 

 external surface of the muscle it covers to the thyroid cartilage. 



The elasticity of this fibrous covering plays a certain part in the move- 

 ments of the hyo-laryngeal apparatus, in acting as a passive antagonist of its 

 depressors. 



This muscle is, and can only be, a perfect constrictor of the pharynx, 

 as it diminishes tho diameter of that cavity in every direction : the longi- 

 tudinal diameter, by means of its posterior fibres, which draw tho thyroid 

 cartilage forward ; and its transverse diameter, by tho circle thrown around 

 the orifice of the Eustachian tubes (Figs. 149 ; 176, 8). 



HYO-PHAKYNGEUS, OB FIBST MIDDLE CONSTRICTOR; THYRO-PHABYNGEUS, 

 OR SECOND MIDDLE CONSTBIOTOB ; AND CBICO-PHABYNOKUS, OB INFERIOR ' 

 CONSTRICTOR. Tho two first of these muscles only form one in Man, tho 

 inlilUi; constrictor of tho pharynx. They are three muscular bands which 

 terminate above tho pharynx, on a median fibrous fold sometimes wide 

 enough to look like an aponourosis. Tho first band arises from tho cornu of 

 the os hyoides: the second, from the external surface of the thyroid carti- 

 lage ; the third, from the superficial face of tho cricoid cartilage. 



