#8 - Scalp and Face

1. Make a skin incision (N1) in the midline from the normal hairline to the suprasternal notch. Cut around the eyelids, nose and mouth. Make lateral incisions along the hairline to a point above the auricle. Using a sharp scalpel blade, reflect skin flaps from the forehead, temporal region, face and neck, being extremely careful to not make the incisions very deep and remove only the skin, because the facial muscles are in the superficial fascia. Do not try to skin the nose.
   
   
2. Remove enough superficial fascia from the forehead and the face to locate the following muscles of facial expression (852/N22) which are attached to the skin:
   
   
   1. Frontal belly of occipitofrontalis (N22) - the epicranial aponeurosis extends from the muscle belly towards the vertex. Make a cut in the aponeurosis and demonstrate the loose connective tissue layer of the scalp deep to it (872/M873).
   2. Orbicularis oculi (N22).
   3. Platysma (N22) - following this muscle up from the neck to the mouth is helpful in determining the plane for other muscles around the mouth.
   4. Orbicularis oris (N22).
   5. Levator Anguli Oris (N22)
   6. Depressor anguli oris (N22).
   7. Depressor labii inferioris (N22).
   8. Zygomaticus major (N22).
   9. Levator labii superioris (N22).
   10. Risorius (N22).
       
       
3. Disturbing facial muscles as little as possible, dissect the facial artery (865/N19) from the angle of the mandible where it is deep to the platysma muscle to its termination at the medial angle of the eye. Locate the superior and inferior labial branches (N32). They are usually sizable vessels. In many instances the facial artery terminates in a superior labial branch and the angular artery is missing. Note the position and course of the facial vein (N19) posterior to the artery.
   
   
4. Locate the parotid duct (N21) in the superficial fascia covering the masseter muscle (870/N21). This is about on a line with the lobe of the ear and can be felt in the living as a hard ridge. At the anterior margin of the masseter the duct turns at a sharp angle and pierces the buccinator muscle (N50), also a muscle of facial expression, to enter the vestibule of the mouth.
   
   
5. Just inferior to the duct find, in the superficial fascia, the buccal branch of the facial nerve (N21) or the zygomatic branch (863/N21) just above the duct. Follow the branch obtained posteriorly into the substance of the parotid gland, several centimeters, until the point of the branching of the facial nerve into its five terminal branches (N21)is reached. Try to follow each of the branches (typically temporal, zygomatic, buccal, mandibular, cervical) to discern the general area of distribution but do not attempt to trace branches to all facial muscles. This nerve is usually the most superficial of the various structures coursing in the substance of the parotid gland and can be followed without endangering deeper structures. Parotid tissue must be removed or pushed aside in order to display the trunk of the facial nerve (N21) and its branches. There is considerable variation in the branching pattern as well as the size of the various branches.
   
   
6. Locate the following:
   
   
   1. Supraorbital artery and nerve (N32) - emerges behind the orbicularis oculi muscle (859/N32).
   2. Superficial temporal artery (N19) and auriculotemporal nerve (N20) - located just anterior to ear (861+ 865).
      
      
7. Carefully incise the tissue overlying the infraorbital and mental foramina (835/N2) and then by pushing the soft tissue aside, reveal the infraorbital nerve (859/N20) with branches to the lower eyelid, lateral nose and upper lip and the mental nerve (861/N20) to the chin and lower lip. Note the upward direction taken by the mental nerve.