FACE AND FRONTAL REGION OF HEAD 125 



The zygomatic head (O.T. zygomaticus minor] springs 

 from the anterior part of the facial surface of the zygomatic 

 bone, under cover of the lower lateral part of the orbicularis 

 oculi. It runs downwards and anteriorly, and is inserted into 

 the lateral part of the upper portion of the orbicularis oris 

 and into the adjacent part of the skin of the upper lip. 



The Infra-orbital Head (O.T. Lev at or Labii Superior is 

 Proprius}. This head springs from the whole length of the 

 infra-orbital border, under cover of the orbicularis oculi. It 

 is inserted into the upper lateral part of the orbicularis oris 

 and the skin of the upper lip. 



The angular head (O.T. levator labii superioris alczque 

 nasi] springs from the frontal process of the maxilla. It 

 broadens as it descends, and it is inserted into the ala of the 

 nose and into the upper part of the orbicularis oris. 



Musculus Zygomaticus. The zygomaticus (O.T. zygo- 

 maticus major) is a comparatively long, slender muscular 

 band which springs from the facial surface of the zygomatic 

 bone, under cover of the lower lateral fibres of the orbicularis 

 oculi and to the lateral side of the zygomatic head of the 

 quadratus labii superioris. Its fibres pass downwards and 

 medially to the angle of the mouth, where some blend with 

 the orbicularis oris and others are inserted into the skin. 



The Risorius. This muscle, when well developed, consists 

 partly of some of the uppermost fibres of the platysma muscle 

 of the neck, which bend anteriorly to the angle of the mouth, 

 and partly of additional fibres which spring from the fascia 

 over the masseter muscle and the parotid gland. Both 

 groups of fibres blend with the fibres of the orbicularis oris 

 at the angle of the mouth. 



Musculus Triangularis. The triangularis (O.T. depressor 

 anguli oris) springs from the oblique line on the lateral surface 

 of the body of the mandible. Its fibres converge as they 

 pass anteriorly and upwards, and, at the angle of the mouth, 

 they blend with the orbicularis oris, in which some of them 

 curve past the angle and terminate in the substance of the 

 upper lip (Figs. 57, 58). 



Musculus Quadratus Labii Inferioris (O.T. Depressor Labii 

 Inferioris). This muscle springs from the lower part of the 

 superficial surface of the mandible, between the mental 

 tubercle and the mental foramen, its posterior border being 

 overlapped by the triangularis. The fibres pass upwards 



