THE EtEAD AND NECK 1269 



process of the ethmoid bone, covered b}- mucous membrane; and 

 above and below the inferior turbinate bone are seen the posterior 

 parts of the middle and inferior meatus. The orifice of the 

 Eustachian tube is situated on each lateral wall, behind and external 

 to the corresponding posterior naris, and on the same level as the 

 posterior end of the inferior turbinate bone. It is somewhat oval, 

 and presents, above and behind, a prominent round border, formed 

 of cartilage, called the cushion. Behind the cushion there is a deep 

 pouch on the lateral wall of the naso- pharynx, called the lateral 

 pharyngeal recess, or fossa of Rosenmuller, which represents the 

 upper part of the phar^mgeal portion of the second \asceral cleft. 

 The mucous membrane extending between the lateral pharyngeal 

 recesses, at the upper and back part, presents a number of folds 

 containing a large amoimt of IjTnphoid tissue, which constitute 

 the pharyngeal tonsil. When enlarged this mass is liable to obstruct 

 the Eustachian orifices, and even the posterior nares. At the 

 lower part of the phan/ngeal tonsil ther-^ may be seen a small 

 median recess, called the pharyngeal bursa, which leads upwards and 

 back\Vards towards the pharyngeal tubercle on the basilar process 

 of the occipital bone. 

 The mucous membrane is covered by ciliated columnar epithelium. 

 Buccal Part of the Pharynx. — This part is situated between the 

 soft palate and the superior aperture of the larynx. Anteriorly it 

 commvmicates with the buccal cavity through the isthmus faucium, 

 below which is the root of the tongue. Each lateral wall presents 

 the posterior pUlar of the fauces, the interval between the two 

 pillars corresponding to the pharyngeal isthmus. In front of each 

 posterior pillar is a triangular depression which lodges the tonsil. 



Laryngeal Part of the Pharynx. — This part is situated behind 

 the lar^Tix. Anterior to it there are the epiglottis, the superior 

 aperture of the lar\Tix, on either side of which is a recess called the 

 sinus pyriformis, and the posterior parts of the arytenoid and 

 cricoid cartilages. With the muscles related to them. It communi- 

 cates with the larynx anteriorly and the oesophagus inferiorly. 



The mucous membrane of the buccal and laryngeal portions is 

 covered by stratified squamous epithelium. 



Blood-supply. — The arteries of the pharynx are derived from 

 several sources, e.g., the ascending pharyngeal branch of the external 

 carotid, the inferior or ascending palatine and tonsillar branches of 

 the cervical part of the facial artery-, and the descending palatine 

 and pterj'go-palatine breinches of the internal maxiUary. 



The veins form a copious pharyngeal plexus, which is disposed 



upon the lateral and posterior walls of the pharjTix. It com- 



j municates superiorly with the pter5'goid venous plexus, and receives 



' tributaries from the soft palate, tonsils, and Eustachian tubes. 



; Inferiorly the blood is conveyed from it into the internal jugular 



vein directly, or through means of the common facial vein. 



Lymphaties. — The lymphatic vessels from the upper part of the 



^ pharynx pass to the internal maxiUary glands. Which are associated 



: with the lateral walls of the tube, and those from the remaining 



