THE HEAD AND NECK. 85 



and the spheno-mandibular ligament. You will see it on the outer surface of the 

 external pterygoid muscle. 



7. The styloid process, muscles and ligaments attached. 



1. The stylo-hyoid muscle. 



2. The stylo-pharyngeus muscle. 



3. The stylo-glossus muscle. 



4. The stylo-mandibular ligament. 



5. The stylo-hyoid ligament. 



Trace each from its styloid origin to its specific insertion. 



Dissection. The above deep structures will be readily found on dividing the 

 temporo-tnandibular ligament. As you do this, notice the interarticular fibro- 

 cartilage. Between the neck of the jaw and the internal lateral ligament find 

 the first stage of the internal maxillary artery. 



The external pterygoid muscle (Fig. 49) originates by two heads : (i) From 

 the outer surface of the external pterygoid plate. (2) From the pterygoid ridge 

 on the outer surface of the greater wing of the sphenoid bone. It has two 

 insertions: (i) Into the interarticular fibro-cartilage of the temporo-mandibular 

 articulation ; (2) into a depression in front of the condyle of the jaw. 



The inferior dental nen>e (Fig. 51) is a branch of the inferior maxillary 

 division of the fifth cranial. It passes between the ramus of the jaw and the 

 spheno-mandibular ligament, in company with an artery of the same name, 

 and enters the inferior dental canal. (Fig. 50.) It throws off in its course 

 dental branches to the teeth ; a large cutaneous branch, the mental, to the 

 skin of the chin. The mental branch comes to the surface through the mental 

 foramen. (Fig. 8.) The inferior dental artery takes the same course and has a 

 similar distribution. (Fig. 5 i .) 



The mylo-hyoid nerve is given off from the inferior dental as the latter is 

 entering the mandibular canal in the mandible. It lies in a groove on the inner 

 surface of the lower jaw, and is covered by the periosteum. It supplies the 

 mylo-hyoid muscle and the anterior belly of the digastric muscle with motion. 



1 . What is the buccal orifice ? 



A transverse slit, bounded by the lips, and terminating laterally in the 

 angles ; by it the mouth communicates with the external world. 



2. What is the isthmus of the fauces f 



It is the buccal opening of the pharynx. It is bounded by the tongue below, 

 soft palate above, and pillars of the fauces laterally, and by it the mouth com- 

 municates with the pharynx. 



3. How is the soft palate made up, and to what is it attached? 



Its special parts are : (i) The uvula ; (2) the anterior and posterior pillars of 

 the fauces ; (3) the tonsillar recess between the pillars. This should be studied 

 on the living subject. 



4. What is the vestibule ? 



The part of the oral cavity bounded by the cheeks and lips externally and 

 the dental arches internally. 



5. What muscle lies under the anterior pillar of llie fauces and helps form the 

 same ? 



The palato-glossus muscle, very readily seen. 



6. What is the action of this muscle ? 



In the act of swallowing it draws the tongue upward and the anterior pillars 

 downward, hood-like, over the back of the tongue ; this closes the buccal orifice 



