THE FACE, MOUTH AND PHARYNX 175 



sides, and in addition each anastomoses with the transverse 

 facial and middle temporal branches of the superficial temporal 

 artery. 



The superior and inferior labial (coronary) branches supply 

 the lips and lie in the submucous tissue. During operations 

 on the lips, these vessels are controlled by an assistant, who 

 grasps the lip between his finger and thumb. It should be 

 remembered that they lie very close to the muco-cutaneous 

 junction. 



The Anterior Facial Vein descends from the medial 

 palpebral commissure (inner canthus), posterior to the external 

 maxillary artery, but its course is much straighter than that of 

 the artery. At its commencement, where it is known as the 

 angular vein (p. 220), it communicates with the ophthalmic 

 veins and therefore indirectly with the cavernous sinus and 

 it terminates by uniting with the posterior facial (p. 176) to form 

 the common facial vein, which joins the internal jugular. If it 

 is involved in an acute infective process, such as carbuncle, 

 septic thrombosis with embolism may occur owing to the absence 

 of valves. The condition may spread in either direction, for 

 if there is any obstruction to the downward flow, the direction 

 of the stream is at once reversed. If it spreads upwards it may 

 cause thrombosis of the cerebral sinuses, but if downwards it 

 may set free septic emboli into the internal jugular vein. Below 

 the zygomatic bone and in front of the masseter the anterior 

 facial vein communicates freely with the pterygoid venous 

 plexus, and this, in its turn, communicates with the cavernous 

 sinus through the foramen ovale and the foramen Vesalii. 

 Infection may reach the cerebral sinuses by this route, either 

 from the anterior facial vein or from the pterygoid plexus. 



The Parotid Gland occupies the interval between the 

 mastoid process and the posterior border of the ramus of the 

 mandible, and its deep part rests on the styloid process. It 

 is limited above by the zygomatic arch and the external acoustic 

 meatus, and below it overlaps the posterior belly of the digastric.. 

 In front it extends on to the surface of the masseter (Fig. 52). 

 It is completely enclosed by a fascial sheath derived from the 

 deep cervical fascia, which sends fibrous septa into the gland. 

 The superficial portion of the sheath is extremely dense and 

 strong, and offers great resistance to any swelling of the parotid 

 or to any enlargement of the lymph glands which lie embedded 

 within it. 



