Welcome to drtbalu's Otolaryngology online
Anatomy of tonsil
Dr. T. Balasubramanian M.S. D.L.O.
A ring of lympnoid tissue surround the naso pharynx and oro pharynx. These lymphoid tissue are collectively known as the waldayer's ring. Waldayer's ring has two components, namely the inner and outer rings. The cervical lymph nodes constitute the outer ring, while the inner ring is constituted by 1. adenoid at the roof of nasopharynx, 2. tubal tonsils or tonsil of Gerlac which surround the pharyngeal ends of eustachean tube. These lymphoid tissue surround the naso pharynx.
The lymphoid tissue surrounding the oropharynx also constituting the components of the inner Waldayer's ring are 1. Lingual tonsil in the posterior 1/3 of the tongue, 2. Palatine tonsils on either side of oro pharynx, and 3. sub epithelial lymphoid tissue found in the posterior pharyngeal wall. All these structures of the inner Waldayer's ring are inter linked.
Functions of Waldayer rings: These Waldayer's rings consitute an antigen sampling center where the extraneous antigens are caught and sampled stimulating the immune mechanism. Antigens from inspired air are trapped by the adenoid and the tubral tonsils. These antigens in turn stimulate release of immunoglobins by the B lymphocytes. To facilitate eposure and trapping of antigens the mucosa covering the adenoid is thrown in to grooves called as furrows. These furrows serve to increase the surface area of the adenoid tissue, similarly antigens from ingested food are captured and sampled by the lingual and palatine tonsils. The mucosa covering the palatine tonsils are thrown in to numerous crypts about 18 - 20 in each tonsil. These crypts serve to increase the surface area of mucosa covering the tonsil.
Figure showing the components of waldayer's ringAnatomy of palatine tonsils: Palatine tonsils are the largest member of the inner waldayer's ring. It is almond shaped and lie on either side of the oropharynx. Develomentally tonsils arise from the ventral portion of the second pharyngeal pouch, i.e. ideally named as sinus tonsillaris. The trace of this sinus is present in tonsil as supra tonsillar cleft.
Figure showing embryology of tonsil
Tonsil is lodged in the tonsillar fossa on either side
of orophayrnx. The tonsillar fossa lies between two pillars,
anterior and the posterior pillars. The anterior pillar is formed
by palato glossus muscle, the posterior pillar is formed by palato
pharyngeus muscle. The outer aspect of tonsil is lined by
condensed capsule formed by the pharyngobasilar fascia a specialised
portion (it is also known to course the surface of the tonsil and
extend into it to form septa that conduct nerves and vessels), deep to
which lie the superior constrictor muscle, lateral to which is the
bucco pharyngeal fascia. The glossopharyngeal nerve and the
stylohoid ligament pass downwards and forwards beneath the lower edge
of the superior constrictor in the lower part of the tonsillar
fossa. These structures collectively constitute the tonsillar
bed. The tonsil is virtually inseparable from its capsule, but the
capsule is united by loose connective tissue to pharyngeal muscles,
hence the tonsillar dissection is carried out in this plane.
The main artery of the tonsil is the tonsillar branch of the facial artery which enters the tonsil near its lower pole by piercing the superior constrictor just above the styloglossus muscle. Other arteries supplying the tonsil are lingual artery through its dorsal lingual branches, ascending palatine branch of facial artery, and ascending pharyngeal vessels.
Venous drainage occurs through the para tonsillar vein, and the vessels also pass through to the pharyngeal plexus or facial vein after piercing the superior constrictor.
Lymphatic vessels from the tonsil pierce through the buccopharyngeal fascia and pass to the upper deep cervial group of nodes, particularly to the jugulodigastric group.
Nerve supply to the
tonsil is from the glossopharyngeal nerve.