Waldeyer’s ring is a collection of lymphoid tissue or follicles in the upper part of digestive system.
This ring is formed by:
Superiorly- Pharyngeal tonsils or Adenoids.
Inferiorly- Lingual tonsil.
Laterally- Palatine tonsils and tubal tonsils.
I. Pharyngeal Tonsil:
Lie postero superiorly under the mucous membrane of the roof and adjoining posterior wall of nasopharynx.
II. Lingual Tonsil:
This is present antero inferiorly and lies under the mucosa of posterior 1/3 of dorsum of tongue.
Collection of lymphoid tissue around the commencement of air and food passages arranged in a ring like patterns called Waldeyer’s lymphatic ring. It prevents invasion of micro-organisms into the air and food passages. The lymph from the ring drains into superficial and deep cervical group of lymph nodes, which form the external ring of Waldeyer.
III. Palatine Tonsils:
Are largest collections of lymphoid tissue present in the tonsillar fossa.
Development – From second pharyngeal pouch.
Boundaries of the tonsillar fossa:
Superiorly- Soft palate
Inferiorly- Dorsal surface of posterior 1/3 of tongue
Anteriorly- Palato glossal arch
Posteriorly- Palato pharyngeal arch
Laterally- Superior constrictor muscle of the pharynx.
Lateral surface is covered with a fibrous – capsule. Between the fibrous capsule and superior constrictor of pharynx, the para tonsillar vein passes downwards. Plica triangularis, is a fold of mucous membrane connects the palato glossal and palatopharyngeal folds superiorly and inferiorly.
Tonsillar bed or floor of the tonsillar fossa is formed by superior constrictor and palato-pharyngeus muscles. It is separated from tonsil by a thick condensation of pharyngobasilar fascia forming capsule. Capsule is separated from superior constrictor muscle by a film of loose areolar tissue containing venous plexus of tonsil.
Characteristic Features of Tonsils:
i. Tonsils are 1st line of defence of the body against bacterial invasion.
ii. Lymphoid tissue produces – antibodies which increases body resistance.
iii. They have no lymph sinus and so tissue fluid is filtered directly in them.
iv. Shape – ovoid – like a large almond (2 cm).
Parts:
Two poles – upper and lower.
Two borders – anterior and posterior.
Two surfaces – medial surface is covered by buccal mucous membrane, i.e., stratified squamous epithelium.
Lateral surface – covered by fibrous capsule – formed by pharyngo – basilar fascia.
Number of septa extends from capsule into tonsil and conduct blood vessels and nerves into it.
Relations:
Medial Surface:
It is covered by pharyngeal mucous membrane and has a superior intra tonsillar cleft (remains of 2nd pharyngeal cleft).
And 12-15 tonsillar crypts that extend deeply into the lymphoid tissue.
The crypts of the tonsil may lodge pus or food particles – causes infection of tonsil.
Lateral surface related to:
a. Superior constrictor of pharynx
b. Facial artery and its two branches
c. Ascending palatine artery and
d. Tonsillar artery.
Posterolateraly are Styloglossus and stylopharyngeus muscles, glossopharyngeal nerve.
Stylohoid ligament – Sometimes – styloid process.
Upper pole- Related to – plica semilunaris
Lower pole- Related to – plica triangularis.
Arterial Supply:
1. Tonsillar branch of facial artery (main).
2. Ascending palatine branch of facial artery.
3. Dorsal lingual branches of lingual artery.
4. Ascending pharyngeal branch of external carotid artery.
5. Descending palatine artery branch of IIIrd part of maxillary artery.
Venous Drainage:
Peri tonsillar venous plexus may be connected to pharyngeal venous plexus via para tonsillar vein – large vein.
Main – tonsillar branch of lingual vein.
Source of bleeding after tonsillectomy.
Nerve Supply:
1. Tonsillar branches of glossopharyngeal nerve.
2. Lesser palatine nerves.
Lymphatic Drianage:
1. Jugulo digastric lymph node – called tonsillar lymph node because it is enlarged in tonsillitis.
2. Deep cervical group of lymph nodes.
IV. Tubal Tonsil:
These are present on each side around the opening of Eustachian tube into nasopharynx.
Applied Anatomy (Tonsil):
1. Tonsils are large in children and retrogress after puberty.
2. Tonsils are site of infection – causes tonsillitis.
3. Peritonsillar abscess – called Quincy – pus is collected in peritonsillar area due to recurrent infection.
4. Tonsilectomy is the surgical removal of large and infected tonsil.
5. Tonsillitis may cause pain in the ear – which is referred pain because both are supplied by glossopharyngeal nerve.
6. Septic focus can cause – pulmonary tuberculosis, meningitis, carditis, and general ill health etc.
7. Tonsils produce antibodies and increases body resistance. They are more useful upto 5 years of age because of low immunity in children they act as safe guard and prevent infection.