|System||Immune system Lymphatic system|
|Latin||Tonsilla, Tonsillae (pl.)|
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, 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. 
|Adenoid (also termed "pharyngeal tonsil")||Ciliated pseudostratified columnar (respiratory epithelium)||Incompletely encapsulated||Small folds—sometimes described as crypts ||Roof of pharynx|
|Tubal tonsils||Ciliated pseudostratified columnar (respiratory epithelium)||Roof of pharynx|
|Palatine tonsils||Non-keratinized stratified squamous||Incompletely encapsulated||Long, branched ||Sides of oropharynx between palatoglossal|
and palatopharyngeal arches
|Lingual tonsils||Non-keratinized stratified squamous||Incompletely encapsulated||Long, unbranched  ||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. 
The adenoid grows until the age of 5, starts to shrink at the age of 7 and becomes very small in adulthood. 
The tonsils are immunocompetent organs which 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 cell (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.  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.  However, different mechanisms of pathogenesis for these two subtypes of tonsillar hypertrophy have been described,  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.[ citation needed ]
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).  Tonsil size may have a more significant impact on upper airway obstruction for obese children than for those of average weight. 
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.
The lymphatic system, or lymphoid system, is an organ system in vertebrates that is part of the immune system, and complementary to the circulatory system. It consists of a large network of lymphatic vessels, lymph nodes, lymphatic or lymphoid organs, and lymphoid tissues. The vessels carry a clear fluid called lymph back towards the heart, for re-circulation.
A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that include B and T cells. Lymph nodes are important for the proper functioning of the immune system, acting as filters for foreign particles including cancer cells, but have no detoxification function.
Palatine tonsils, commonly called the tonsils and occasionally called the faucial tonsils, are tonsils located on the left and right sides at the back of the throat, which can often be seen as flesh-colored, pinkish lumps. Tonsils only present as "white lumps" if they are inflamed or infected with symptoms of exudates and severe swelling.
Tonsillectomy is a surgical procedure in which both palatine tonsils are fully removed from the back of the throat. The procedure is mainly performed for recurrent tonsillitis, throat infections and obstructive sleep apnea (OSA). For those with frequent throat infections, surgery results in 0.6 fewer sore throats in the following year, but there is no evidence of long term benefits. In children with OSA it results in improved quality of life.
In anatomy, the adenoid, also known as the pharyngeal tonsil or nasopharyngeal tonsil, is the superior-most of the tonsils. It is a mass of lymphatic tissue located behind the nasal cavity, in the roof of the nasopharynx, where the nose blends into the throat. In children, it normally forms a soft mound in the roof and back wall of the nasopharynx, just above and behind the uvula.
Adenoidectomy is the surgical removal of the adenoid for reasons which include impaired breathing through the nose, chronic infections, or recurrent earaches. The effectiveness of removing the adenoids in children to improve recurrent nasal symptoms and/or nasal obstruction has not been well studied. The surgery is less commonly performed in adults in whom the adenoid is much smaller and less active than it is in children. It is most often done on an outpatient basis under general anesthesia. Post-operative pain is generally minimal and reduced by icy or cold foods. The procedure is often combined with tonsillectomy, for which the recovery time is an estimated 10–14 days, sometimes longer, mostly dependent on age.
Tonsillitis is inflammation of the tonsils in the upper part of the throat. It can be acute or chronic. Acute tonsillitis typically has a rapid onset. Symptoms may include sore throat, fever, enlargement of the tonsils, trouble swallowing, and enlarged lymph nodes around the neck. Complications include peritonsillar abscess.
Tonsil stones, also known as tonsilloliths, are mineralizations of debris within the crevices of the tonsils. When not mineralized, the presence of debris is known as chronic caseous tonsillitis (CCT). Symptoms may include bad breath. Generally there is no pain, though there may be the feeling of something present.
The lingual tonsils are a collection of lymphatic tissue located in the lamina propria of the root of the tongue. This lymphatic tissue consists of the lymphatic nodules rich in cells of the immune system (immunocytes). The immunocytes initiate the immune response when the lingual tonsils get in contact with invading microorganisms.
Gut-associated lymphoid tissue (GALT) is a component of the mucosa-associated lymphoid tissue (MALT) which works in the immune system to protect the body from invasion in the gut.
Myeloid tissue, in the bone marrow sense of the word myeloid, is tissue of bone marrow, of bone marrow cell lineage, or resembling bone marrow, and myelogenous tissue is any tissue of, or arising from, bone marrow; in these senses the terms are usually used synonymously, as for example with chronic myeloid/myelogenous leukemia.
The mucosa-associated lymphoid tissue (MALT), also called mucosa-associated lymphatic tissue, is a diffuse system of small concentrations of lymphoid tissue found in various submucosal membrane sites of the body, such as the gastrointestinal tract, nasopharynx, thyroid, breast, lung, salivary glands, eye, and skin. MALT is populated by lymphocytes such as T cells and B cells, as well as plasma cells and macrophages, each of which is well situated to encounter antigens passing through the mucosal epithelium. In the case of intestinal MALT, M cells are also present, which sample antigen from the lumen and deliver it to the lymphoid tissue. MALT constitute about 50% of the lymphoid tissue in human body. Immune responses that occur at mucous membranes are studied by mucosal immunology.
Germinal centers or germinal centres (GCs) are transiently formed structures within B cell zone (follicles) in secondary lymphoid organs – lymph nodes, ileal Peyer's patches, and the spleen – where mature B cells are activated, proliferate, differentiate, and mutate their antibody genes during a normal immune response; most of the germinal center B cells (BGC) are removed by tingible body macrophages. The B cells develop dynamically after the activation of follicular B cells by T-dependent antigen.
Waldeyer's tonsillar ring is a ringed arrangement of lymphoid organs in the pharynx. Waldeyer's ring surrounds the naso- and oropharynx, with some of its tonsillar tissue located above and some below the soft palate.
Adenoid hypertrophy is the unusual growth (hypertrophy) of the adenoid first described in 1868 by the Danish physician Wilhelm Meyer (1824–1895) in Copenhagen. He described a long term adenoid hypertrophy that will cause an obstruction of the nasal airways. These will lead to a dentofacial growth anomaly that was defined as "adenoid facies".
Adenoiditis is the inflammation of the adenoid tissue usually caused by an infection. Adenoiditis is treated using medication or surgical intervention.
The pharynx is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea. It is found in vertebrates and invertebrates, though its structure varies across species. The pharynx carries food and air to the esophagus and larynx respectively. The flap of cartilage called the epiglottis stops food from entering the larynx.
The human palatine tonsils (PT) are covered by stratified squamous epithelium that extends into deep and partly branched tonsillar crypts, of which there are about 10 to 30. The crypts greatly increase the contact surface between environmental influences and lymphoid tissue. In an average adult palatine tonsil the estimated epithelial surface area of the crypts is 295 cm2, in addition to the 45 cm2 of epithelium covering the oropharyngeal surface.
Lymph node stromal cells are essential to the structure and function of the lymph node whose functions include: creating an internal tissue scaffold for the support of hematopoietic cells; the release of small molecule chemical messengers that facilitate interactions between hematopoietic cells; the facilitation of the migration of hematopoietic cells; the presentation of antigens to immune cells at the initiation of the adaptive immune system; and the homeostasis of lymphocyte numbers. Stromal cells originate from multipotent mesenchymal stem cells.
The avian immune system is the system of biological structures and cellular processes that protects birds from disease.