Makindo Medical Notes

🧩 Anatomy of the Pharynx

The pharynx is a muscular tube (~12–14 cm long) connecting the nasal and oral cavities to the larynx and esophagus. It acts as a common pathway for both air and food. The pharynx is divided into three main regions: the nasopharynx, oropharynx, and laryngopharynx. It plays vital roles in breathing 🌬️, swallowing 🍽️, speech 🗣️, and immune defense 🛡️.

📍 Divisions of the Pharynx

• 👃 Nasopharynx:
  • Posterior to the nasal cavity, superior to the soft palate.
  • Passageway for air only.
  • Contains pharyngeal tonsils (adenoids) and openings of the Eustachian tubes ➝ pressure equalisation with the middle ear (important in otitis media in children).
• 👅 Oropharynx:
  • Posterior to the oral cavity, extends from the soft palate to the hyoid bone.
  • Pathway for both air and food.
  • Contains palatine tonsils and lingual tonsils.
  • Soft palate elevates during swallowing to prevent nasal regurgitation.
• 🎤 Laryngopharynx (Hypopharynx):
  • Posterior to the larynx, extends from the hyoid bone to the esophagus.
  • Food directed into esophagus; air directed into larynx.
  • Epiglottis covers laryngeal inlet during swallowing ➝ protects against aspiration.

💪 Muscles of the Pharynx

The pharynx has constrictors (for propulsion) and longitudinal muscles (for elevation). They coordinate during swallowing (pharyngeal phase of deglutition).

• Constrictor Muscles:
  • Superior: Contracts nasopharynx ➝ prevents regurgitation into nose.
  • Middle: Narrows pharynx.
  • Inferior: Pushes bolus into esophagus; contains the cricopharyngeus, forming the upper esophageal sphincter.
• Longitudinal Muscles:
  • Stylopharyngeus: Elevates pharynx (CN IX).
  • Palatopharyngeus: Elevates pharynx, narrows cavity.
  • Salpingopharyngeus: Elevates pharynx, opens Eustachian tube.

🩸 Blood Supply of the Pharynx

• Arterial: Ascending pharyngeal, facial, maxillary (branches of external carotid).
• Venous: Pharyngeal venous plexus ➝ internal jugular vein.

🧠 Nerve Supply of the Pharynx

• Motor: All pharyngeal muscles by vagus nerve (CN X), except stylopharyngeus (CN IX).
• Sensory:
  • Nasopharynx ➝ CN V2.
  • Oropharynx ➝ CN IX (important in gag reflex afferent).
  • Laryngopharynx ➝ CN X.

⚡ Functions of the Pharynx

• Swallowing (Deglutition): Sequential constrictor contractions propel food ➝ esophagus.
• Respiration: Conducts air ➝ larynx & trachea.
• Speech: Resonating chamber for phonation.
• Immune Defense: Waldeyer’s ring of tonsils traps pathogens at entry points.

💡 Clinical Pearls

• ❗ Killian’s dehiscence: Weak area between inferior constrictor fibers ➝ site of Zenker’s diverticulum.
• 👂 Recurrent otitis media in children often due to enlarged adenoids obstructing Eustachian tubes.
• 🤮 Gag Reflex: CN IX = afferent, CN X = efferent.
• 🫁 Aspiration risk increases with pharyngeal muscle weakness (e.g., post-stroke).