Drainage of Pharynx

🩸 Drainage of the Pharynx - Blood Supply, Lymphatic Drainage, Nerve Supply

🩺 Blood Supply of the Pharynx

The pharynx has a rich arterial supply, primarily from branches of the external carotid artery.

🩸 ARTERIAL SUPPLY

Five major arteries contribute to the blood supply:

• Ascending pharyngeal artery (branch of medial external carotid artery)
  • Supplies the superior part of the pharynx, soft palate, internal pharynx, and Eustachian tube.
• Tonsillar artery (branch of facial artery)
• Ascending palatine branch (branch of facial artery)
• Superior laryngeal artery (branch of superior thyroid artery)
• Inferior laryngeal artery (branch of inferior thyroid artery, from thyrocervical trunk of the subclavian artery)

💉 VENOUS DRAINAGE

• Drained by internal submucosal and external pharyngeal venous plexus.
• These plexuses are located predominantly on the posterior aspect of the middle constrictor muscle.
• They drain into:
  • Internal jugular vein
  • Pterygoid venous plexus (via connections)

🧬 Lymphatic Drainage of the Pharynx

The lymphatic drainage of the pharynx is complex and rich, making metastatic spread common in pharyngeal malignancies.

1️⃣ Nasopharynx

Drains into:

• Retropharyngeal lymph nodes (first station; includes the important Node of Rouvière)
• Deep cervical lymph nodes (Level II most commonly involved)

What is the % of involvement of different nodes in nasopharyngeal carcinoma?

2️⃣ Oropharynx

• Lymphatic vessels pierce the superior constrictor muscle.
• Drain into:
  • Deep cervical lymph nodes
  • Especially the Jugulodigastric (Tonsillar) Node
  • Also drains to Levels II and III (though isolated lower drainage is rare).

3️⃣ Hypopharynx (Laryngopharynx)

Drains into:

• Level II, III, and IV deep cervical nodes
• Level III is most commonly involved.

🧠 Nerve Supply of the Pharynx

The motor and sensory innervation of the pharynx is mainly through the pharyngeal plexus.

🔗 PHARYNGEAL PLEXUS FORMATION

Formed by communications between:

• Pharyngeal branches of the Vagus nerve (CN X)
• Pharyngeal branches of the Glossopharyngeal nerve (CN IX)
• Sympathetic fibers from the Superior Cervical Ganglion

These nerves run on the posterolateral surface of the pharynx and supply deeper pharyngeal layers.

⚙️ MOTOR SUPPLY

• Motor fibers originate from the cranial root of the Accessory nerve, carried by the vagus nerve.

• Supplies:

  • All pharyngeal muscles (except the stylopharyngeus)
  • Stylopharyngeus is supplied by the glossopharyngeal nerve (CN IX).
  • Cricothyroid muscle (of larynx) is supplied by the external and recurrent laryngeal nerves.

🧏 SENSORY SUPPLY

• Oropharynx: Glossopharyngeal nerve (CN IX)

• Laryngopharynx: Internal laryngeal nerve (branch of Superior laryngeal nerve, Vagus CN X)

• Nasopharynx: Maxillary nerve (V2) via the Pterygopalatine ganglion

• Palate: Greater and Lesser Palatine nerves (branches of Pterygopalatine ganglion)