Otolaryngology: Anatomy & Physiology

Triangles of the Neck

Anterior Triangle

  • Borders:
    • Superior: Mandible
    • Lateral: SCM (Anterior Border)
    • Medial: Midline
  • Contains: Carotid Sheath

Posterior Triangle

  • Borders:
    • Anterior: SCM (Posterior Border)
    • Posterior: Trapezius
    • Inferior: Clavicle
  • Contains: Spinal Accessory Nerve & Brachial Plexus

Submental Triangle

  • Borders:
    • Inferior: Hyoid
    • Lateral: Anterior Belly of the Digastric
    • Medial: Midline
  • Floor: Mylohyoid
  • Within the Anterior Triangle

Submandibular Triangle

  • Borders:
    • Superior: Mandible
    • Anterior: Anterior Belly of the Digastric
    • Posterior: Posterior Belly of the Digastric
  • Within the Anterior Triangle

Deep Cervical Space

Deep Cervical Fascia Layers

  • Superficial (Investing) Layer of the Deep Cervical Fascia
    • Encloses the Major Muscles (Trapezius, Sternocleidomastoid & Straps)
  • Middle (Pretracheal) Layer of the Deep Cervical Fascia
    • Encloses the Pharynx, Esophagus, Larynx, Trachea & Thyroid
  • Deep (Prevertebral) Layer of the Deep Cervical Fascia
    • Encloses the Vertebral Column & Paraspinal Muscles

Deep Cervical Fascial Spaces

  • Primary Spaces:
    • Submandibular Space – Contained within the Submandibular & Submental Triangles
    • Parapharyngeal Space – Contained in the Lateral Neck Around the Pharynx
      • Forms an Inverted Cone with Base at the Skull and Apex at the Hyoid Bone
      • Communicates with the Carotid Sheath
    • Retropharyngeal Space – Contained Behind the Pharynx
      • Communicates with the Carotid Sheath & Danger Space
      • Also Communicates Directly to the Superior Mediastinum
  • Secondary Spaces:
    • Danger Space – Contained Posterior to the Retropharyngeal Space
      • Bounded Anteriorly by Alar Fascia & Posteriorly by Prevertebral Fascia
      • Communicates Freely into the Posterior Mediastinum – Allows Contiguous Spread Between the Neck & Chest
    • Carotid Sheath
      • Communicates with the Superior Mediastinum at the Aortic Arch (“Lincoln’s Highway”)
    • Prevertebral Space
    • Pretracheal Space
    • Peritonsillar Space
    • Parotid Space
    • Temporal Fossa Space
    • Infratemporal Space
    • Pterygomaxillary Fossa
    • Masticator Space

Passages

Pharynx

  • Nasopharynx – Skull Base to Soft Palate
    • Continuous with the Nasal Cavity
  • Oropharynx – Soft Palate to Epiglottis
  • Laryngopharynx – Epiglottis to Cricoid Cartilage
    • Posterior to the Larynx
    • Continuous with the Esophagus

Larynx

  • From Epiglottis to Cricoid Cartilage
  • Anterior to the Laryngopharynx
  • Continuous with the Trachea
  • Subsections:
    • Supraglottis – Space Above the Vocal Cords
    • Glottis – Vocal Cords
    • Subglottis – Space Below the Vocal Cords

Trachea

  • From Cricoid Cartilage to the Primary Bronchi
  • First Complete Cartilaginous Ring: Cricoid Cartilage

Esophagus

  • Cricoid Cartilage to Stomach

Vascular Supply

Thyrocervical Trunk

  • Branch of the Subclavian Artery
  • Branches:
    • Suprascapular Artery
    • Transverse Cervical Artery
    • Ascending Cervical Artery
    • Inferior Thyroid Artery

External Carotid Artery

Nerves

Superior Laryngeal Nerve (SLN)

  • Path:
    • Branches off the Vagus Nerve
    • Travels Lateral to the Thyroid Gland
  • Branches:
    • External Branch
      • Function: Cricothyroid Muscle
      • Deficit: Voice Fatigue & Projection (Opera Singers) Mn
    • Internal Branch
      • Function: Pharynx & Epiglottis Sensation Above Vocal Cords
      • Deficit: Poor Cough/Aspiration
  • Most Commonly Injured Nerve During a Thyroidectomy
    • Avoid Injury by Ligating Superior Vessels Close to the Thyroid

Recurrent Laryngeal Nerve (RLN)

  • Path:
    • Branches off the Vagus Nerve
    • Loops:
      • Left Loops Under the Aortic Arch
      • Right Loops Under the Subclavian Artery
    • Ascends Up the Tracheoesophageal Groove
    • Travels Posterior to the Thyroid Gland
  • Function:
    • Motor: Larynx & Vocal Cords (Not Cricothyroid Muscle)
    • Sensory: Larynx Below Vocal Cords
  • Deficit: Cord Fixed in Paramedian/Adducted Position
    • Hoarseness (Unilateral) & Obstruction (Bilateral)
  • Non-Recurrent Laryngeal Nerve
    • Direct Patch, Does Not Loop
    • Most Common on the Right
      • Can Have Both RLN & Non-RLN Simultaneously on the Right
      • Associated with Arteria Lusoria (Aberrant Right Subclavian)
    • Left-Sided NRLN is Associated with a Right-Sided Aortic Arch
    • Higher Risk of Injury

Other Nerves

Lymphatics

Cervical Lymph Node Levels Mn

  • I
    • Ia: Submental
    • Ib: Submandibular Triangle
      • Separated by Anterior Digastric
  • II: Upper Jugular
    • IIa: Anterior to Accessory Nerve
    • IIb: Posterior to Accessory Nerve
  • III: Middle Jugular (Hyoid to Inferior Cricoid)
  • IV: Lower Jugular
  • V: Posterior Triangle (Behind SCM)
    • Va: Superior to Cricoid
    • Vb: Inferior to Cricoid
  • VI: Central
    • Boundaries: Hyoid, Carotid Artery, Sternal Notch

Waldeyer’s Ring

  • A Ring of Lymphatic Tissues Located at the Entrance of the Respiratory/Alimentary Tracts
  • Components:
    • Palatine Tonsils
    • Nasopharyngeal (Adenoid) Tonsils
    • Lingual Tonsil
  • Considered Mucosa-Associated Lymphoid Tissue (MALT)
  • First Site of Defense Against Inhaled/Ingested Microorganisms

Salivary Glands

Parotid Gland

  • Wraps Around the Mandibular Ramus
  • Largest Salivary Gland
  • Produces 20% of Saliva
  • Drains Through the Parotid (Stensen) Duct
  • Secretions: Serous
  • The Only Salivary Gland with Intra-Glandular Lymph Nodes
  • Divided into a Superficial & Deep Lobe
    • Facial Nerve Branches Travel Between the Lobes

Submandibular Gland

  • Second Largest Salivary Gland
  • Lies Below the Mandible, Superior to the Digastric Muscles
  • Produces 65-70% of Saliva (Despite Being Smaller than the Parotid Gland)
  • Secretions: Serous & Mucin

Sublingual Gland

  • Lies Below the Tongue, Anterior to the Submandibular Gland
  • Drains Through 8-20 Excretory (Rivinus) Ducts Directly into the Oral Cavity
  • Secretions: Mucin (Primarily) & Serous

Secretions

  • Serous: Alpha-Amylase (Enzymatic Digestion)
  • Mucinous: Mucin (Lubricant)

Mnemonics

Deficit of Superior Laryngeal Nerve Injury

  • Need “Superior” to Hit the “High” Notes

Cervical Lymph Node Level “Modified Handy Mnemonic”

  • Fingers #1-3 Out & Placed Over the Contralateral Neck – Thumb to the Chin
    • I: Distal Thumb
    • II-IV: Index Down (Distal II, Middle III, Proximal IV)
      • Running Over the SCM
    • V: Middle (Vulgar Middle Finger Gets a Whole Number)
    • VI: Proximal Thumb