Anatomy of Tonsil - Parts, Functions, Blood Supply, Nerve Supply, Applied Anatomy

🧠 Anatomy of Tonsil

The Palatine tonsils are paired lymphoid structures forming an important part of Waldeyer’s ring.

📍 Location of the Tonsil

• Tonsils are two in number, one on each side

• Located on the lateral wall of the oropharynx

• Lie in the tonsillar fossa, between Anterior pillar & Posterior pillar.

• Covered laterally by a tonsillar capsule

Which muscles form the Anterior pillar and Posterior pillar of Tonsillar Fossa?

📐 Size & Shape of Tonsil

🔹 Size (Age Related Changes)

• Enlarges rapidly at 5-6 years

• Maximum size at puberty

• Gradual involution after puberty

• Minimal lymphoid tissue in old age

🔹 Pathological Variation

• Acute tonsillitis → enlarged tonsils

• Chronic tonsillitis → shrunken, fibrotic tonsils

🔹 Shape

• Ovoid mass of lymphoid tissue

• Long axis runs superior → inferior

• Fixed anatomical position

🧩 Parts of the Tonsil

Each tonsil has:

• Two poles

  • Upper pole
  • Lower pole

• Two surfaces

  • Medial surface
  • Lateral surface

🔝 Upper Pole of Tonsil

• Extends into the soft palate

• Covered by semilunar fold

• Fold encloses a potential space: Supratonsillar fossa

What is the Clinical importance of the Upper Pole of Tonsil?

🔻 Lower Pole of Tonsil

• Attached to the tongue

• A triangular mucosal fold from anterior pillar encloses: Anterior tonsillar space

• Separated from tongue by: Tonsillolingual sulcus

What is the Clinical importance of the Tonsillolingual sulcus?

👅 Medial Surface of Tonsil

1- Epithelium

What is the Epithelial lining of the tonsil?

2- Tonsillar Crypts

• Epithelium dips inward forming 12–15 crypts

• One large crypt: Crypta magna / intratonsillar cleft

What does crypta magna represent embryologically?

3- Secondary Crypts

• Branch from primary crypts

• Can fill with:

  • Desquamated epithelium
  • Bacteria
  • Food debris

🧱 Lateral Surface & Capsule of Tonsil

• Covered by fibrous tonsillar capsule

• Between capsule & tonsillar bed lies:

  • Loose areolar tissue
  • Paratonsillar vein

• This space is:

  • Peritonsillar space

What is the clinical importance of Peritonsillar space?

🛏️ Tonsillar Bed (Very Important Viva Topic)

🔹 Structures (Medial → Lateral)

1. Tonsillar capsule
2. Loose areolar tissue (paratonsillar vein)
3. Pharyngobasilar fascia
4. Superior constrictor muscle
5. Buccopharyngeal fascia
6. Styloglossus muscle
7. Glossopharyngeal nerve
8. Facial artery branches
9. Medial pterygoid muscle
10. Submandibular gland
11. Angle of mandible

📌 Must remember sequence for viva

📘 In my detailed notes, I’ve mentioned a mnemonic to remember the structures of Tonsil bed easily.

🩸 Blood Supply of Tonsil

🔴 Arterial Supply of Tonsil

1. Tonsillar artery – ⭐ Main supply

2. Ascending palatine artery

3. Ascending pharyngeal artery

4. Dorsal lingual branches

5. Descending palatine artery

📌 Tonsillar artery enters via inferior pole after piercing superior constrictor

What are the parent branches of each of the arteries supply the tonsil?

🔵 Venous Drainage of Tonsil

• Via pharyngeal venous plexus

• Key vein:

  • Paratonsillar vein
  • Also called external palatine vein

What is the applied importance of Paratonsillar vein?

🧬 Lymphatic Drainage of Tonsil

• Lymphatics pierce superior constrictor

• Drain into: Upper deep cervical lymph nodes

• Most important node: Jugulodigastric node

How would you locate the Jugulodigastric node?

🧠 Nerve Supply of Tonsil

• Via tonsillar plexus

• Formed by:

  • Tonsillar branches of glossopharyngeal nerve
  • Fibers from maxillary nerve via lesser palatine nerve

📌 Important for referred otalgia

🛡️ Function of Tonsil

• Part of Waldeyer’s ring

• Acts as first line of defense

• Guards upper aerodigestive tract against:

  • Bacteria
  • Viruses
  • Other antigens (inhaled/ingested)

What is Waldeyer’s ring? What are the different components of Waldeyer’s ring?

⚕️ Applied Anatomy of Tonsil

• Referred Otalgia

What is Referred Otalgia? What are the different nerves involved and causes of Referred Otalgia?

• Peritonsillar Abscess (Quinsy)

What is Quinsy? How does a patient with Quinsy present? What is it's management?

• Post Tonsillectomy Hemorrhage

Which structure involvement most commonly causes Post Tonsillectomy Hemorrhage?

• Internal Carotid Artery Relation

  • Lies 2.5 cm posterolateral to tonsil
  • Important during deep dissection

📌 Exam Pearls

• Crypta magna → 2nd pharyngeal pouch
• Jugulodigastric node → tonsillar lymph drainage
• Paratonsillar vein → post-tonsillectomy bleed
• Glossopharyngeal nerve → referred ear pain
• Tonsillolingual sulcus → carcinoma risk