Levator Labii Superioris Proprius.
Levator Anguli Oris.
Zygomaticus major.
Zygomaticus minor.

The Levator Labii Superioris Proprius is a thin muscle of a quadrilateral form. It arises from the lower margin of the orbit immediately above the infra-orbital foramen, some of its fibres being attached to the superior maxilla, some to the malar bone; its fibres converge downwards and inwards to be inserted into the muscular substance of the upper lip.

Relations. By its superficial surface, with the lower segment of the Orbicu-laris palpebrarum; below, it is sub-cutaneous. By its deep surface, it conceals the origin of the Compressor nasi and Levator anguli oris muscles, and the infra-orbital vessels and nerves, as they escape from the infra-orbital foramen.

The Levator Anguli Oris (musculus caninus) arises by a broad attachment from the canine fossa, immediately below the infra-orbital foramen; its fibres incline downwards and a little outwards, to be inserted into the angle of the mouth, intermingling its fibres with those of the Zygomatici, the Depressor anguli oris, and the Orbicularis.

Relations. Its superficial surface, is covered above by the Levator labii supe-rioris proprius and the infra-orbital vessels and nerves; below, by the integument. By its deep surface, it is in relation with the superior maxilla, the Buccinator, and the mucous membrane.

The Zygomaticus major is a slender cylindrical fasciculus, winch arises from the malar bone, in front of the zygomatic suture, and, descending obliquely downwards and inwards, is inserted into the angle of the mouth, where it blends with the fibres of the Orbicularis and Depressor anguli oris.

Relations. By its superficial surface, occasionally with the Orbicularis palpe-brarum, above; and below, with the sub-cutaneous adipose tissue. By its deep surface, with the malar bone, the Masseter and Buccinator muscles.

The Zygomaticus minor arises from the malar bone, in front of the Zygomaticus major, immediately behind the maxillary suture, and, passing downwards and inwards, is continuous with the outer margin of the Levator labii superioris proprius.

Relations. By its superficial surface, with the integument and the Orbicularis palpebrarum above. By its deep surface, with the Levator anguli oris.

Nerves. This group of muscles is supplied by the facial nerve.

Actions. The Levator labii superioris proprius is the proper elevator of the upper lip, carrying it at the same time a little outwards. The Levator anguli oris raises the angle of the mouth and draws it inwards; whilst the Zygomatici raise the upper lip, and draw it somewhat outwards, as in laughing.