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AN36.1-7 | Mouth, Pharynx & Palate — Part 2
Waldeyer's Lymphatic Ring and Pharyngeal Spaces (AN36.4, AN36.5)
Waldeyer's lymphatic ring:
A ring of lymphoid tissue guarding the gateway to the respiratory and alimentary tracts.
| Component | Location |
|---|---|
| Pharyngeal tonsil (adenoids) | Posterior wall, roof of nasopharynx |
| Tubal tonsils | Around the pharyngeal opening of Eustachian tube |
| Palatine tonsils | Tonsillar fossae (the largest and most clinically relevant) |
| Lingual tonsil | Base of tongue (posterior 1/3) |
| Lateral pharyngeal bands | Posterior pharyngeal wall |
Function: first-line immunological defence (IgA secretion) against inhaled and ingested antigens.
Clinical: Waldeyer's ring is the most common site for extranodal lymphoma in the head and neck (B-cell non-Hodgkin's lymphoma).
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Pharyngeal Spaces (AN36.5):
| Space | Location | Clinical significance |
|---|---|---|
| Parapharyngeal space | Between the pterygomandibular raphe laterally and the pharynx medially; extends from skull base to hyoid | Abscess from tonsils, parotid, teeth → can compress ICA, IJV |
| Retropharyngeal space | Between posterior pharyngeal wall and alar fascia | Retropharyngeal abscess → danger space → mediastinitis |
| Pterygomandibular space | Between medial pterygoid and mandibular ramus | Site for inferior alveolar nerve block injection |
Pyriform fossa (sinus):
- Located in the laryngopharynx (hypopharynx), lateral to the aryepiglottic fold
- Has the internal laryngeal nerve and superior laryngeal vessels running in its mucosa (submucosally)
- Clinically: site of lodgement of foreign bodies (fish bones) → sharp pain localised to the side
- Pyriform sinus fistula (third pharyngeal pouch remnant) → left-sided neck abscess recurring with upper respiratory infections in children
SELF-CHECK
A. Retropharyngeal abscess; alar fascia
B. Right peritonsillar abscess (quinsy); the pharyngeal constrictor and capsule of the tonsil
C. Right parapharyngeal abscess; the pterygomandibular raphe
D. Ludwig's angina; the mylohyoid muscle
Reveal Answer
Answer: .
This is a classic peritonsillar abscess (quinsy) — pus in the peritonsillar space (between the tonsillar capsule and the superior constrictor). The uvula deviates to the LEFT (away from the abscess). Trismus is from irritation of the medial pterygoid muscle. The tonsil capsule + superior pharyngeal constrictor separate the peritonsillar space from the deep parapharyngeal space.
Killian's Dehiscence and Pharyngeal Pouch (AN36.7)
Killian's dehiscence:
A triangular weak area in the posterior wall of the pharynx between:
- Oblique fibres of the thyropharyngeus (inferior constrictor — upper part)
- Horizontal fibres of the cricopharyngeus (inferior constrictor — lower part = upper oesophageal sphincter)
These two parts of the inferior constrictor have different orientations, creating a zone of muscular weakness at the back of the pharynx above the cricopharyngeus.
Zenker's diverticulum (pharyngeal pouch):
- Pulsion diverticulum (mucosa + submucosa herniate, no muscle layer)
- Herniates posteriorly through Killian's dehiscence, then laterally (usually to the left)
- Occurs in elderly patients (>60 years)
Clinical features:
- Regurgitation of undigested food (sometimes hours after eating)
- Halitosis (retained food)
- Progressive dysphagia (pouch enlarges and compresses oesophagus)
- Neck gurgling, sensation of a lump in the throat
- Risk: aspiration pneumonia (regurgitated food inhaled)
- Risk: endoscopic perforation — if a rigid oesophagoscopy is performed without awareness of the pouch, the scope enters the pouch and perforates
Treatment: Endoscopic stapling of the cricopharyngeal bar (divides the cricopharyngeus and septa between pouch and oesophagus) or open surgery (diverticulectomy + cricopharyngeal myotomy).
SELF-CHECK
A. Pulsion diverticulum through Killian's dehiscence — the weak area between the thyropharyngeus and cricopharyngeus
B. Traction diverticulum from tuberculous lymph nodes pulling on the anterior oesophageal wall
C. Herniation through the piriform fossa mucosa
D. Congenital branchial arch remnant in the posterior pharyngeal wall
Reveal Answer
Answer: .
Zenker's diverticulum is a pulsion diverticulum that herniates through Killian's dehiscence — the triangular weak point between the oblique fibres of the thyropharyngeus and the horizontal fibres of the cricopharyngeus. Raised intraluminal pressure (especially during cricopharyngeal dysfunction) forces mucosa through this gap.
SELF-CHECK
A. Submental node (Level IA)
B. Jugulodigastric node (Level IIA)
C. Virchow's node (left supraclavicular)
D. Jugulo-omohyoid node (Level III)
Reveal Answer
Answer: .
The jugulodigastric node (Level IIA) is the sentinel node for oropharyngeal structures including the tonsil, posterior tongue, and soft palate. It lies at the junction of the internal jugular vein and the posterior belly of digastric. The jugulo-omohyoid node (Level III) is the sentinel node for the tongue body.
CLINICAL PEARL
The dangerous tonsil relationship — internal carotid artery: The internal carotid artery lies approximately 2.5 cm lateral to the medial surface of the tonsil, separated only by the superior pharyngeal constrictor and the fascia. In cases of tonsillar carcinoma with deep invasion, or a tortuous ICA (relatively more common in the elderly, and in some South Indian populations), the ICA can bulge into the tonsillar fossa. Always palpate the tonsil before attempting peritonsillar drainage. A pulsatile mass in the tonsillar fossa is NOT a quinsy — it is a vascular anomaly or aneurysm. Blind incision into a tortuous ICA is catastrophic. If in doubt, do a CT angiogram before any intervention.