Tonsils

 WALDEYER'S LYMPHATIC RING 

In relation to the naso-oropharyngeal isthmus, there are several aggregations of lymphoid tissue that constitute Waldeyer's lymphatic ring. 

The most important aggregations are the right and left palatine tonsils usually referred to simply as the tonsils.
Posteriorly and above, there is the nasopharyngeal tonsil; 

laterally and above, there are the tubal tonsils, 

inferiorly, there is the lingual tonsil over the posterior part of the dorsum of the tongue. 

Hypertrophy or enlargement of the nasopharyngeal tonsil or adenoids may obstruct the posterior nasal aperture and may interfere with nasal respiration and speech, leading to mouth breathing. 

These tonsils usually regress by puberty. 

Hypertrophy of the tubal tonsil may occlude the auditory or pharyngotympanic tube leading to middle ear problems 

Palatine Tonsils 

Features 

The palatine tonsil occupies the tonsillar sinus or fossa between the palatoglossal and palatopharyngeal arches
It can be seen through the mouth. 

The tonsil is almond-shaped.
It has two surfaces medial and lateral; two borders, anterior and posterior two poles, upper and lower.
The medial surface is covered by stratified 

squamous epithelium continuous with that of the mouth. 

This surface has 12 to 15 crypts.
The largest of these is called the intratonsillar cleft. 

The lateral surface is covered by a sheet of fascia which forms the hemi-capsule of the tonsil.
• The capsule is an extension of the pharyngobasilar fascia.
• It is only loosely attached to the muscular wall of the pharynx, 

formed here by the superior constrictor and by the styloglossus,
but anteroinferiorly the capsule is firmly adherent to the side of the tongue (suspensory ligament of tonsil) just in front of the insertion of the palatoglossus and the palatopharyngeus muscle. 

• This firm attachment keeps the tonsil in place during swallowing.
  
• The tonsillar artery enters the tonsil by piercing the superior constrictor just behind the firm attachment
  
• The palatine vein or external palatine or paratonsillar vein
  descends from the palate in the loose areolar tissue on the lateral surface of the capsule, and crosses the tonsil before piercing the wall of the pharynx.
  
• The vein may be injured during removal of the tonsil or tonsillectomy 

The bed of the tonsil is formed from within outwards by,

• a. The pharyngobasilar fascia.
• b. The superior constrictor and palatopharyngeus muscles.
• c. The buccopharyngeal fascia.
• In the lower part, the styloglossus.
  
• The glossopharyngeal nerve.
  
• Still more laterally, there are the facial artery with its tonsillar and ascending palatine branches.
  
• The internal carotid artery is 2.5 cm posterolateral to the tonsil.
  

The anterior border is related to the palatoglossal arch with its muscle.
The posterior border is related to the palatopharyngeal arch with its muscle. 

The upper pole is related to the soft palate, and
the lower pole, to the tongue.
The plica triangularis is a triangular vestigial fold of mucous membrane covering the anteroinferior part of the tonsil. 

The plica semilunaris, is a similar semilunar fold that may cross the upper part of the tonsillar sinus.
The intratonsillar cleft is the largest crypt of the tonsil. It is present in its upper part. 

The mouth of cleft is semilunar in shape and parallel to dorsum of tongue.
It represents the internal opening of the second pharyngeal pouch. 

A peritonsillar abscess or quinsy often begins in this cleft. 

Arterial Supply 

1. Main source: Tonsillar branch of facial artery.
2. Additional sources:
a. Ascending palatine branch of facial artery. 

b. Dorsal lingual branches of the lingual artery. 

c. Ascending pharyngeal branch of the external carotid artery.
d. The greater palatine branch of the maxillary artery 

Venous Drainage 

One or more veins leave the lower part of deep surface of the tonsil, pierce the superior constrictor, and join  the palatine, pharyngeal, or facial veins. 

Lymphatic Drainage 

Lymphatics pass to jugulodigastric node. 

There are no afferent lymphatics to the tonsil. 

Nerve Supply 

Glossopharyngeal and lesser palatine nerves. 

Development 

The tonsil develops from ventral part of second pharyngeal pouch.
The lymphocytes are mesodermal in origin 

Applied Anatomy

The tonsils are large in children. They retrogress after puberty. 

The tonsils are frequently sites of infection, specially in children. Infection may spread to surrounding tissue forming a peritonsillar abscess. 

Enlarged and infected tonsils often require surgical removal.
The operation is called Tonsillectomy.
Tonsillectomy is usually done by guillotine method.
Haemorrhage after tonsillectomy is checked by removal of clot from the raw tonsillar bed. This is compared with the method for checking postpartum haemorrhage. These are the only two organs in the body where bleeding is checked by removal of clots. In other parts of the body, clot formation is encouraged. 

Tonsillitis may cause referred pain in the ear as glossopharyngeal nerve supplies both these areas. Suppuration in the peritonsillar area is called quinsy.
A peritonsillar abscess is drained by making an incision in the most prominent point of the abscess. 

Tonsils are often sites of a septic focus. Such a focus can lead to serious disease like pulmonary tuberculosis, meningitis, etc. and is often the cause of general ill health 

Watch the lectures on YouTube:

Palatine Tonsils | Situation | Features | Relations | Blood & Nerve Supply | Lymphatic Drainage |