Anatomy of the Parotid Gland

The Parotid Gland

• Bilateral salivary gland located in the face, producing serous saliva (watery solution rich in enzymes) to lubricate and aid in food breakdown in the oral cavity
• Anatomical position:
  • Divided into deep and superficial lobes, separated by the facial nerve
  • Lies within the parotid region, bounded by:
    • Superiorly: Zygomatic arch
    • Inferiorly: Inferior border of the mandible
    • Anteriorly: Masseter muscle
    • Posteriorly: External ear and sternocleidomastoid

Secretions and Duct

• Secretions are transported to the oral cavity by the Stensen duct
• Duct:
  • Arises from the anterior surface of the gland, traversing the masseter muscle
  • Pierces the buccinator, moving medially to enter the vestibule of the mouth opposite the upper second molar tooth

Anatomical Relationships

• Clinically important during parotid gland surgery
• Neurovascular structures passing through the gland:
  • Facial nerve (CN VII): gives rise to five terminal branches, innervating muscles of facial expression
  • External carotid artery: gives rise to the posterior auricular artery within the parotid gland
  • Retromandibular vein: formed by the convergence of the superficial temporal and maxillary veins, responsible for venous drainage of the face

Blood Supply and Drainage

• Arterial supply: posterior auricular and superficial temporal arteries, both branches of the external carotid artery
• Venous drainage: retromandibular vein

Innervation

• Receives sensory and autonomic innervation
• Autonomic innervation controls the rate of saliva production
• Sensory innervation supplied by the auriculotemporal nerve (gland) and the great auricular nerve (fascia)
• Parasympathetic innervation:
  • Begins with the glossopharyngeal nerve
  • Reaches the gland via the lesser petrosal nerve to the otic ganglion
  • Auriculotemporal nerve carries parasympathetic fibers from the otic ganglion to the parotid gland
• Sympathetic innervation:
  • Originates from the superior cervical ganglion (part of the paravertebral chain)
  • Fibers travel along the external carotid artery to reach the parotid gland

Lymphatic Drainage

• Numerous lymph nodes distributed throughout and around the substance of the parotid gland
• Nodes are distributed in both superficial and deep lobes
• Majority of nodes (about 90%) are found in the superficial node
• Nodes drain various structures, including:
  • External acoustic meatus, auricle, scalp, eyelids, and lacrimal glands
  • Soft palate, middle ear, and nasopharynx

The Buccal Fat Pad

• Encapsulated fat mass in the cheek, located between the buccinator muscle and several superficial muscles
• Inferior portion is contained within the buccal space
• Implicated in the formation of hollow cheeks and the nasolabial fold, but not in the formation of jowls
• Composed of several parts, including:
  • Anterior, intermediate, and posterior lobes
  • Four extensions: sublevator, melolabial, buccal, and pterygoid

Clinical Relevance: Disorders of the Parotid Gland

• Parotid gland tumors:
  • Most common site of salivary gland tumors
  • Usually benign, such as an adenolymphoma
  • Treatment involves surgical excision of the tumor and parotid gland (parotidectomy)
• Parotitis:
  • Inflammation of the parotid gland, usually due to infection
  • Pain referred to the external ear due to the auriculotemporal nerve
• Parotid duct injury:
  • May be damaged in facial injuries or during surgical operations
  • Duct is superficial, passing forward across the masseter about a fingerbreadth below the zygomatic arch
• Parotid salivary gland and lesions of the facial nerve:
  • Benign parotid neoplasm rarely causes facial palsy
  • Malignant tumor of the parotid is highly invasive and may involve the facial nerve, causing unilateral facial paralysis
• Frey's syndrome:
  • Interesting complication that develops after penetrating wounds of the parotid gland
  • Characterized by beads of perspiration on the skin covering the parotid when eating
  • Caused by damage to the auriculotemporal and great auricular nerves