The tonsils are a set of lymphoid organs facing into the aerodigestive tract, which is known as Waldeyer's tonsillar ring and consists of the adenoid tonsil (or pharyngeal tonsil), two tubal tonsils, two palatine tonsils, and the lingual tonsils. These organs play an important role in the immune system.
When used unqualified, the term most commonly refers specifically to the palatine tonsils, which are two lymphoid organs situated at either side of the back of the human throat. The palatine tonsils and the adenoid tonsil are organs consisting of lymphoepithelial tissue located near the oropharynx and nasopharynx (parts of the throat).
Humans are born with four types of tonsils: the pharyngeal tonsil, two tubal tonsils, two palatine tonsils and the lingual tonsils.[1]
Type |
Capsule |
Location |
||
|---|---|---|---|---|
Pharyngeal tonsil (also termed "adenoid") |
Incompletely encapsulated |
Small folds—sometimes described as crypts1 |
Roof of pharynx |
|
Ciliated pseudostratified columnar (respiratory epithelium) |
Roof of pharynx |
|||
Incompletely encapsulated |
Long, branched2 |
Sides of oropharynx
between palatoglossal |
||
Non-keratinized stratified squamous |
Incompletely encapsulated |
Behind terminal sulcus (tongue) |
The palatine tonsils tend to reach their largest size in puberty, and they gradually undergo atrophy thereafter. However, they are largest relative to the diameter of the throat in young children. In adults, each palatine tonsil normally measures up to 2.5 cm in length, 2.0 cm in width and 1.2 cm in thickness.[2]
The adenoid grows until the age of 5, starts to shrink at the age of 7 and becomes small in adulthood.
The tonsils are immunocompetent organs that serve as the immune system's first line of defense against ingested or inhaled foreign pathogens, and as such frequently engorge with blood to assist in immune responses to common illnesses such as the common cold. The tonsils have on their surface specialized antigen capture cells called microfold cells (M cells) that allow for the uptake of antigens produced by pathogens. These M cells then alert the B cells and T cells in the tonsil that a pathogen is present and an immune response is stimulated.[3] B cells are activated and proliferate in areas called germinal centers in the tonsil. These germinal centers are places where B memory cells are created and secretory antibody (IgA) is produced.
The palatine tonsils can become enlarged (adenotonsillar
hyperplasia) or inflamed
(tonsillitis). The most common way to treat
tonsillitis is with anti-inflammatory
drugs such as
ibuprofen, or if bacterial in origin,
antibiotics, e.g.
amoxicillin and
azithromycin. Surgical removal
(tonsillectomy) may be advised if the
tonsils obstruct the airway or
interfere with swallowing, or in patients with severe or recurrent
tonsillitis.[4] However, different mechanisms
of pathogenesis for these two subtypes of tonsillar hypertrophy have
been described,[5] and may have different responses to identical
therapeutic efforts. In older patients, asymmetric tonsils (also known
as asymmetric tonsil hypertrophy) may be an indicator of virally
infected tonsils, or tumors such as
lymphoma or squamous cell
carcinoma.
A tonsillolith (also known as a "tonsil stone") is material that accumulates on the palatine tonsil. This can reach the size of a peppercorn and is white or cream in color. The main substance is mostly calcium, but it has a strong unpleasant odor because of hydrogen sulfide and methyl mercaptan and other chemicals.[6]
Palatine tonsil enlargement can affect speech, making it hypernasal and giving it the sound of velopharyngeal incompetence (when space in the mouth is not fully separated from the nose's air space).[7] Tonsil size may have a more significant impact on upper airway obstruction for obese children than for those of average weight.[8]
As mucosal lymphatic tissue of the aerodigestive tract, the palatine tonsils are viewed in some classifications as belonging to both the gut-associated lymphoid tissue (GALT) and the mucosa-associated lymphoid tissue (MALT). Other viewpoints treat them (and the spleen and thymus) as large lymphatic organs contradistinguished from the smaller tissue loci of GALT and MALT.
File:Blausen 0859 Tonsils&Adenoids.png|Illustration of frontal view of tonsils
[1]
[2]
[3]
[4] Tonsilitis {{!}} Lymph Nodes | work = MedlinePlus | publisher = U.S. National Library of Medicine |access-date=2017-01-29|language=en}}
[5]
[6]
[7]
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