894 THE VASCULAR SYSTEM. 



(d) The submental branch arises from the external maxillary just as the latter vessel 

 turns round the inferior border of the mandible. It is the largest branch given off in the 

 neck, and it runs forwards, on the lateral surface of the mylo-hyoid muscle, and medial to 

 the upper part of the submaxillary gland, to the symphysis menti ; there it turns upwards, 

 round the margin of the mandible, and it terminates by anastomosing with branches of the 

 mental and inferior labial arteries. In the neck the submental artery supplies the mylo- 

 hyoid muscle, and the submaxillary and sublingual glands, the latter by a branch which 

 perforates the mylo-hyoid muscle. It anastomoses with the mylo-hyoid branch of the 

 inferior alveolar and with the sublingual artery. In the face it supplies the structures of 

 the lower lip, and anastomoses with the mental branch of the inferior alveolar, and with 

 the inferior labial branches of the external maxillary artery. 



In the Face. (e) The inferior labial branch (O.T. inferior coronary) arises from the 

 front of the external maxillary artery below the level of the angle of the mouth. It runs 

 medially, deep to the triangularis, the quadratus labii inferioris, and the orbicularis oris. 

 In the substance of the lower lip it lies close to the mucous membrane and anastomoses, in 

 the median plane, with its fellow of the opposite side. It supplies the structures in its 

 immediate neighbourhood. 



(/) The superior labial (O.T. superior coronary) springs from the front of the external 

 maxillary about the level of the angle of the mouth. It runs medially, between the orbi- 

 cularis oris and the mucous membrane of the upper lip, to the median plane, supplying the 

 skin, muscles, and mucous membrane of the upper lip, and, by a septal branch, the lower 

 and anterior part of the septum of the 'nose. It anastomoses with its fellow of the 

 opposite side, with the lateral nasal, and, on the septum nasi, with the septal branch of 

 the spheno-palatine artery. 



(g) The masseteric branch, sometimes represented by several twigs, arises from the 

 posterior aspect of the facial trunk, a short distance above the lower margin of the mandible. 

 It passes upwards and posteriorly, across the masseter, and anastomoses with the trans- 

 verse facial artery. 



(h) The buccal is an inconstant branch which, when present, arises from the posterior 

 aspect of the external maxillary artery above the masseteric branch. It runs upwards and 

 posteriorly, across the buccinator muscle, to anastomose with the buccinator branch of the 

 internal maxillary artery. 



(i) The lateral nasal springs from the external maxillary at the point where it 

 becomes the angular. It ramifies on the ala of the nose, supplying the skin, muscles, and 

 alar cartilages, and anastomosing with the angular branch, with the dorsal nasal branch 

 of the ophthalmic, and with branches of the spheno-palatine artery. 



(J) The angular artery is the continuation of the external maxillary beyond the origir 

 of the lateral nasal branch. It runs upwards, in the angular head of the quadratus 3abi 

 superioris, to the medial commissure of the eye, where it anastomoses with the lateral nasal 

 and with the nasal and palpebral branches of the ophthalmic artery. 



In addition to the above-named branches another branch, formerly called the inferio 

 labial, springs from the anterior aspect of the external maxillary below the level of th< 

 alveolar border of the mandible. This vessel runs medially, under cover of the muscles o 

 the lower lip, and it anastomoses with the mental branch of the inferior alveolar artery 

 with the inferior labial (O.T. inferior coronary), and with its fellow of the opposite side. 



(4) Arteria Occipitalis. The occipital artery (Figs. 759, 760, 787) arises fron 

 the posterior aspect of the external carotid artery, below the posterior belly o 

 the digastric muscle, and terminates, near the medial end of the superior nucha 

 line of the occipital bone, by dividing into medial and lateral terminal branches. 



Course. It commences in the carotid triangle and runs upwards and posteriorly 

 parallel with and under cover of the posterior belly of the digastric, to the interve 

 between the transverse process of the atlas and the base of the skull ; there it turn 

 posteriorly, in a groove on the lower surface of the mastoid portion of the tempon 

 bone ; as it leaves the groove it alters its direction and runs upwards and medial!; 

 on the superior oblique muscle, to the junction of the medial and intermedia! 

 thirds of the superior nuchal line of the occipital bone, where it pierces the dee 

 fascia of the neck and enters the superficial fascia of the scalp. 



Relations. In the first or ascending part of its^course the occipital artery cross 

 successively the internal carotid artery, the hypoglossal nerve, the vagus nerve, the intern 

 jugular vein, and the accessory nerve; it is covered by the lower fibres of the posteri 



