Facial Anatomy

Orbicularis Oculi

• origin: Medial orbital margin; medial palpebral ligament; lacrimal bone
• insertion: skin around the margin of the orbit; superior and inferior tarsal planes
• Function:
  • palpebral part arises from the medial palpebral ligament to close the eyes softly (blinking/sleeping) to keep the cornea from drying out
  • lacrimal part passes posterior to the lacrimal sac and draws the eyelids medially, aiding drainage of tears
  • orbital part overlies the orbital rim and attaches to the frontal and maxillary bones for tightly squeezing the eye shut

Muscles of the lips

The mediolus

The mediolus is found just laterally to the angle of the mouth (the labial commissure) and is the point where the fibres of the buccinator, contributing to orbicularis oris, cross each other (the lower fibres to the upper lip and central/upper fibres to the lower lip).  Many other facial muscles also cross this point.  It is responsible for dimples.

Nerve Supply

All the muscles of facial expression are formed from the 2nd pharyngeal arch and are innervated by CNVII (facial nerve).  Note the buccinator is a muscle of facial expression (not mastication- supplied by V3).

• CN VII arises in the pons; travels through the internal auditory meatus, through the facial canal, out the stylomastoid foramen, enters the parotid gland and divides into 5 branches radiating to all regions of the face:
  • Temporal (frontalis muscle)
  • Zygomatic (Orbicularis oculi)
  • Buccal (buccinator/upper lip)
  • Mandibular (muscles of lower lip)- NB overlies the submandibular gland and can be damaged easily at surgery- lower lip droop and dribbling
  • Cervical (platysma- the sheet of muscle overlying the SCM)

Occipitofrontalis muscle

The epicranial aponeurosis is firmly bound to the overlying skin by highly vascular dense connective tissue, but has a layer of loose connective tissue between it and the periosteum of the skull, so it is mobile.

Sensation to the face

• CN V (trigeminal)
  • Ophthalmic (V1) supplies the forehead and upper eyelid, and tip of the nose
  • Maxillary (V2) supplies the lower lid, some of the nos, upper cheek and upper lip
  • Mandibular (V3) supplies the lower cheek, lower lip and skin over the mandible (except over the angle of the mandible which is the great auricular nerve (C1/2))