1234 



THE ORGANS OF DIGESTION 



The muscular coat has been already described (pp. 395 to 398). 



The motor nerves are derived chiefly from the pharyngeal plexus; the Tensor palati, however, 

 receives a special branch from the otic ganglion. The senior filaments are derived from the 

 descending palatine and nasopalatine, and from the glossopharyngeal nerve. 



The Lymphatic Pharyngeal Ring. This name was applied by Waldeyer to the lymphatic 

 structures gathered into a sort of ring about the pharynx. There are three chief collections of 

 this tissue on each side. The first is known as the lingual tonsil (p. 1221); the second as the 

 palatal tonsil (p. 1232); and the third as the pharyngeal tonsil (p. 1232). 



OPENING OF 

 PAROTID DUCT 



GENIO- 



HYOGLOSSUS 

 MUSCLE 



BURSA BENEATH 

 HYOID BONE 



THYROID 

 CARTILAGE 



CRICOID 

 CARTILAGE 



PHARYNGEAL 

 URSA 



ORIFICE OF 

 EUSTACHIAN TUBE 



PHARYNGEAL 

 TONSIL 



SOFT PALATE 

 NASOPHARYNX 



ANTERIOR PALA- 

 TINE ARCH 

 - POSTERIOR PALA- 

 TINE ARCH 

 TONSIL 

 CAVITY OF 

 PHARYNX 

 TONSILLAR 

 SINUS 



POSTERIOR PALA- 

 TINE ARCH 



EPIGLOTTIS 



SINUS 



PYRIFORMIS 



ARYTENO- 



EPIGLOTTIC 



FOLD 



CUNEIFORM 



CARTILAGE 



ARYTENOID 

 CARTILAGE 



OISOPHAGUS 



RING OF 

 RACHEA 



FIG. 950. Sagittal median section of the head and neck. The head is thrown backward into complete extension, 

 which explains the relations between the lower jaw and the hyoid bone as seen in the figure. (Luschka.) 



Development of the Pharynx. The pharynx develops from the cephalic portion of the 

 foregut, flanked by the five branchial (visceral) arches, with four intervening branchial clefts 

 (visceral pouches). These have become retrogressively modified in that they have lost their 

 respiratory function (as gills), but recur in the development of each individual for the purpose 

 of forming organs not entirely vestigial. Thus, the first or most cephalic branchial arch assists 

 in the formation of the jaws, the malleus, incus, sphenomandibular ligament, and part of the 

 external ear. The second arch forms the styloid process, lesser cornu of hyoid and the inter- 

 vening stylohyoid ligament, the stapes, a part of the external ear, and a part of the posterior one- 

 third of the tongue. From the third arch are formed the body and greater cornu of the hyoid 

 bone, and part of the posterior one-third of the tongue. The fourth and fifth arches share in 

 forming the thyroid cartilage. The inner furrows or clefts, lined by entoderm, contribute to 



