Facial Anatomy & Parotid Gland Quiz

Superficial Face

• The superficial face is comprised of facial features, muscles of facial expression, perfusion and drainage patterns, the parotid gland, and its innervation.
• Skin landmarks include glabella, philtrum, nasolabial fold, mentolabial fold/sulcus, labial commissure, oral fissure, and nasal ala.
• Buccal fat pads are prominent in newborns and help support suckling. They protect neurovasculature. Unlike other facial fat, it stays consistent in size and shape with age.
• The superficial musculoaponeurotic system (SMAS) is a continuous network of collagen, elastic fibers, muscle fibers, and adipose tissue. Facial nerve branches become more superficial and lie within the SMAS.

Learning Objectives

• List the muscles of facial expression and describe their actions.
  • Understand the significance of the facial expression muscles and their function in controlling the orbit, nose, and mouth openings.
  • Explain the function of the SMAS.
• Detail the three divisions of the trigeminal nerve and describe the type of axons they contain, which foramina they are traveling through, and their relationships with other structures.
• Define the trigeminal and geniculate ganglion.
• Describe the pathway of the facial nerve, its exit from the skull, and the branches leading to the face.
• Describe the external carotid artery branches and tributaries of the internal jugular vein system for the face.
• Identify the parotid gland and its duct. Explain which structures travel through it and its autonomic innervation.

Muscles of Facial Expression

• Lie within superficial fascia and originate from bone (or deep fascia) or other facial muscles. They are anchored to skin via the SMAS.
• Exhibit emotion and control the openings of the facial skeleton (they act as sphincters around the eyes, mouth, and nares).
• All are innervated by facial nerve branches.
• Organized into 4 groups: epicranial, circumorbital/palpebral, nasal, buccolabial
• Individual muscles in each group will be further studied and detailed for their specific actions.

Parotid Gland

• The largest salivary gland.
• Located anterior to the external ear, superficial to the masseter muscle and the ramus of the mandible. Extends between the zygomatic arch and angle of mandible.
• Structures that pass through the gland include the facial nerve proper and its branches, auriculotemporal nerve, external carotid artery, superficial temporal vessels, transverse facial vessels, and maxillary vessels. Also, the retromandibular vein.
• The parotid gland accounts from 2-6% of head and neck neoplasms. 80-90% of these are benign, but 70-80% of parotid neoplasms are benign masses that present as painless swelling. Treatment typically involves a parotidectomy (either total or partial).
• Parotid capsule (parotid fascia): a tough, connective tissue layer that encloses the parotid gland consisting of deep (cervical fascia) and superficial (SMAS) layers of fascia.

Mumps

• A viral infection that affects major salivary glands.
• Initial symptoms are similar to the flu; a key symptom is swelling of the salivary glands
• An inflamed parotid gland causes pre-auricular pain that is exacerbated during mealtime.
• Prevention is possible via the MMR vaccine (about 86% effective).

Parotid Duct

• Also known as Stenson's duct
• Travels medially, over a muscle, and then pierces the muscle.
• Opens into the oral cavity at the parotid papilla.

Facial Vasculature

• Blood supply to the face and scalp predominantly comes from branches of the external carotid artery (8 branches):
  • Superior thyroid a., Ascending pharyngeal a., Lingual a., Facial a., Occipital a., Posterior auricular a., Maxillary a., and Superficial temporal a.
• Branches of the internal carotid artery (ICA) (supratrochlear & supraorbital) also play a minor role.
• The branches of the ECA and ICA anastomose extensively, which needs to be considered by clinicians.
• Venous drainage: Facial v. runs posterior to facial artery, continuing superiorly as angular v., which communicates with the ophthalmic veins and cavernous sinus; communicates with the deep facial vein, and pterygoid plexus → cavernous sinus = an unfortunate anastomosis). Retromandibular vein is formed by superficial temporal v and maxillary v, and travels within theparotid gland. It then travels to the internal or external jugular v.
• Danger triangle: area of the face from the upper lip to the bridge of the nose where infection could spread to the cavernous sinus.

Innervation

• Trigeminal nerve provides sensory innervation to the face. It gives rise to 3 divisions: ophthalmic (V1), maxillary (V2), and mandibular (V3).
• Trigeminal does NOT contain parasympathetic fibers
• The Facial nerve provides motor innervation to the muscles of facial expression and arises from the pons, with its geniculate ganglion.
• The glossopharyngeal nerve provides motor and sensory innervation, including preganglionic parasympathetic fibers that synapse in the otic ganglion.