Laryngopharynx

The laryngopharynx, also known as the hypopharynx, is the lower part of the pharynx, connecting the oropharynx to the esophagus and larynx.^[1] It serves as a passageway for both food and air, playing a critical role in swallowing and directing food into the esophagus while preventing it from entering the airway.^[8]

Anatomy

Location and Boundaries

• Superior Border: Starts at the level of the hyoid bone (C3 vertebra).
• Inferior Border: Extends down to the cricoid cartilage (C6 vertebra), where it continues as the esophagus.
• Anterior Boundary: Adjacent to the larynx.
• Posterior Boundary: Rests against the prevertebral fascia.

Subdivisions

• Piriform Recess (Sinus):
  • Located on either side of the laryngeal inlet.^[4]
  • Funnels food toward the esophagus and serves as a common site for foreign body entrapment.^[7]
• Postcricoid Region:
  • Positioned behind the cricoid cartilage, playing a role in swallowing and esophageal entry.

Histology

• Epithelium: Lined by non-keratinized stratified squamous epithelium, which withstands mechanical stress from food passage.
• Muscular Layer: Contains inferior pharyngeal constrictors that help propel food during swallowing.

Functions of the Laryngopharynx

Swallowing (Deglutition):

• Coordinates with the epiglottis to close the airway during swallowing, preventing aspiration.
• Contracts to push food into the esophagus.

Respiration: Serves as an air passage when breathing, allowing air to move between the pharynx and larynx. Pathway for Food and Fluids: Acts as a conduit for food and liquids, guiding them toward the esophagus while diverting them away from the trachea.^[5] Protection Against Aspiration: Works with the epiglottis and vocal cords to ensure that food and liquids do not enter the trachea during swallowing.

Clinical Significance

• Laryngopharyngeal Reflux (LPR): Reflux of stomach acid into the laryngopharynx, causing irritation, throat clearing, hoarseness, and chronic cough.
• Cancer of the Laryngopharynx: Often associated with smoking, alcohol, and HPV infection. Symptoms include difficulty swallowing (dysphagia), sore throat, and ear pain.
• Foreign Body Entrapment: The piriform recesses are prone to trapping foreign objects, such as fish bones, which may cause discomfort and require removal.
• Pharyngeal Diverticulum (Zenker’s Diverticulum): A pouch that can form in the posterior wall of the laryngopharynx, leading to difficulty swallowing, regurgitation, and aspiration.
• Aspiration Pneumonia: Dysfunction of the laryngopharynx can lead to food or liquid entering the airway, causing respiratory infections.^[2]
• Nerve Damage: The laryngopharynx is innervated by the vagus nerve (CN X) and its branches (superior and recurrent laryngeal nerves). Damage to these nerves can result in swallowing difficulties and voice changes.

The laryngopharynx is a vital structure for the processes of swallowing and breathing.^[3] Its anatomical design and muscular coordination ensure smooth passage of food while protecting the airway, making it critical to both respiratory and digestive systems.