THE MUSCULAR SYSTEM 63 



The inferior constrictor arises from the cricoid and thy- 

 roid cartilages, and is inserted into its fellow of the opposite 

 side. Action, constricts the pharynx during swallowing. 



The middle constrictor has its origin in the hyoid bone 

 and stylohyoid ligament. Insertion, into its fellow of the 

 opposite side. Action, same as inferior constrictor. 



The superior constrictor arises from the pterygoid plate 

 and palate bone, as well as from the hyoid. Insertion, 

 into the occipital bone. Action, same as inferior con- 

 strictor. 



The stylopharyngeus arises from the inner side of the 

 base of the styloid process of the temporal bone; it is 

 inserted into the thyroid cartilage and blends with the 

 constrictor muscles. Action, elevates the pharynx. 



The palatopharyngeus has its origin in the soft palate. 

 Insertion, into the thyroid cartilage and side of the 

 pharynx. Action, closes the posterior fauces. 



All the muscles just described, except the palatopharyn- 

 geus, are controlled by the spinal accessory, glossopharyn- 

 geal, pharyngeal plexus, external and recurrent laryngeal 

 nerves; the palatopharyngeus is controlled by the palato- 

 glossus nerve. 



The Pharynx. The pharynx is a musculomembranous 

 sac, about 5 inches long, extending from under the base 

 of the skull to a point corresponding to the sixth cervical 

 vertebra. It is widest above and narrowest below, where 

 it terminates in the esophagus. It is attached to the 

 styloid processes of the temporal bone, and presents seven 

 openings: the two posterior nares, two Eustachian tubes, 

 the mouth, the larynx, and the esophagus. For purposes 

 of description it is divided into three parts nasal, oral, 

 and laryngeal. It is attached to two cartilages the 

 cricoid and the thyroid and has three coats an internal 

 mucous membrane, a middle fibrous layer, and an external 

 muscular coat. 



