656 ORGANS OF DIGESTION. 



THE PHARYNX. 



The Pharynx is that part of the alimentary canal which is placed behind the 

 nose, mouth, and larynx. It is a musculo-membranous sac, somewhat conical in 

 form, with the base upwards, and the apex downwards, extending from the under 

 surface of the skull to the cricoid cartilage in front, and the fifth cervical vertebra 

 behind. 



The pharynx is about four inches and a half in length, and broader in the 

 transverse than in the antero-posterior diameter. Its greatest breadth is opposite 

 the cornua of the hyoid bone; its narrowest point at its termination in the 

 03sophagus. It is limited, above, by the basilar process of the occipital bone; 

 below, it is continuous with the oesophagus ; posteriorly, it is connected by loose 

 areolar tissue with the cervical portion of the vertebral column, and the Longi 

 colli and Eecti capitis antici muscles ; anteriorly, it is incomplete, and is attached 

 in succession to the internal pterygoid plate, the ptery go-maxillary ligament, the 

 lower jaw, the tongue, hyoid bone, and larynx ; laterally, it is connected to the 

 styloid processes and their muscles, and is in contact with the common and 

 internal carotid arteries, the internal jugular veins, and the eighth, ninth, and 

 sympathetic nerves, and, above, with a small part of the Internal pterygoid 

 muscles. 



It has seven openings communicating with it; 'the two posterior nares, the two 

 Eustachian tubes, the mouth, larynx, and oesophagus. 



The posterior nares are the two large apertures situated at the upper part of 

 the anterior wall of the pharynx. 



The two Eustachian tubes open one at each side of the upper part of the pharynx, 

 at the back part of the inferior meatus. Below the nasal fossae are the posterior 

 surface of the soft palate and uvula, the large aperture of the mouth, the base of 

 the tongue, the epiglottis, and the cordiform opening of the larynx. 



The cesophageal opening is the lower contracted portion of the pharynx. 



Structure. The pharynx is composed of three coats ; a mucous coat, a muscular 

 layer, and a fibrous coat. 



The fibrous coat is situated between the mucous and muscular layers, and is 

 called the pharyngeal aponeurosis. It is thick above, where the muscular fibres 

 are wanting, and firmly connected to the basilar process of the occipital and petrous 

 portion of the temporal bones. As it descends, it diminishes in thickness, and is 

 gradually lost. 



The mucous coat is continuous with that lining the Eustachian tubes, the nares, 

 the mouth, and the larynx. It is covered by columnar ciliated epithelium, as low 

 down as a level with the floor of the nares ; below that point, it is of the squamous 

 variety. 



The muscular coat has been already described (p. 262). 



The pliaryngeal glands are of two kinds, the simple or compound follicular, 

 which are found in considerable numbers beneath the mucous membrane, through- 

 out the entire pharynx ; and the racemose, which are especially numerous at the 

 upper part of the pharynx, and form a thick layer, across the back of the fauces, 

 between the two Eustachian tubes. 



THE (ESOPHAGUS. 



The (Esophagus is a membranous canal, about nine inches in length, extending 

 from the pharynx to the stomach. It commences at the lower border of the 

 cricoid cartilage, opposite the fifth cervical vertebra, descends along the front of 

 the spine, through tLe posterior mediastinum, passes through the Diaphragm, and, 

 entering the abdomen, terminates at the cardiac orifice of the stomach, opposite the 

 ninth dorsal vertebra. The general direction of the oesophagus is vertical ; but it 

 presents two or three slight curvatures in its course. At its commencement, it is 



