What are tonsils?

Quick Answer
The palatine tonsils are two compact bodies of lymphoid tissue located laterally between the opening of the mouth and the pharynx.
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Structure and Functions

The palatine tonsils are the largest bodies of lymphoid tissue in Waldeyer’s ring. In contrast to the adenoid and lingual tonsil tissues, which are diffuse and adherent to the nasopharynx and the base of the tongue, the palatine tonsils are encapsulated by a specialized fascia and are easily dissected from their muscle beds. The tonsil tissues have ten to thirty deep crypts that extend into each tonsil and are lined by stratified squamous epithelium. Each tonsil sits in a tonsillar fossa in the lateral wall of the opening between the mouth and the pharynx. This tonsil bed is composed of three muscles that hold the tonsil in place. The anterior pillar of the tonsil is formed by the palatoglossus muscle, the posterior pillar is formed by the palatopharyngeal muscle, and the floor of the tonsil bed is formed by the superior constrictor muscle of the pharynx. The tonsils get their blood supply primarily at their lower pole from branches of the dorsal lingual and facial arteries. The tonsils’ main nerve supply is from the tonsillar branches of the glossopharyngeal nerve.

The tonsils are immunologically active lymphatic organs. The lymphocytes of tonsil tissues are approximately composed of 60 percent B lymphocytes and 40 percent T lymphocytes. The location of the tonsils in the upper part of the aerodigestive tract exposes them to many airborne allergens. Tonsil crypts are able to trap foreign material and transport it to lymphoid follicles. When stimulated by antigens, B cells can proliferate in the germinal centers of the tonsils and produce all five major antibody classes. It has been shown that the immunologic activity of the tonsils and the adenoids in Waldeyer’s ring helps protect the entire upper aerodigestive tract. Tonsils are most immunologically active between the ages of four and ten. Although it has been a point of controversy over the years, there is no evidence that removing the tonsils results in any immunologic deficiency.

Disorders and Diseases

Acute tonsillitis is commonly caused by both virus and bacteria. Enlargement of the tonsils without exudates is common with the common cold virus. Epstein-Barr virus may cause mononucleosis with high fever, dysphagia, and tonsillitis characterized by thick gray exudates. The most common bacterial infection of the tonsils is group A streptococcus, which is most commonly seen in children at age five to six years. Before antibiotics, acute streptococcal tonsillitis was a frequent precursor of rheumatic fever.

Recurrent tonsillitis and chronic tonsil hypertrophy are the most common reason for performing tonsillectomy in children. Enlarged tonsils can contribute to airway obstruction and sleep apnea. A peritonsillar abscess is more likely to be seen in young adults. The abscess usually forms between the tonsil and the anterior pillar, causing pain, dysphagia, and drooling, and requires drainage. The combination of exudates and bacteria in the crypts of the tonsils can lead to the formation of plugs or stones called tonsilloliths that can cause pain and bad breath. In severe cases, this condition may also be an indication for tonsillectomy.

Cancer of the palatine tonsil accounts for less than 1 percent of all cancers. Men are affected four times more frequently than women, with an age range between fifty and seventy. More than 70 percent of malignancies are squamous cell carcinomas, with lymphoma accounting for most other tonsil malignancies. Risk factors for squamous cell carcinoma include smoking, drinking alcohol, and infection from HPV.

Perspective and Prospects

Tonsillectomy is one of the oldest recorded surgical procedures, with the first removal of tonsils being described by the Roman surgeon Aulus Cornelius Celsus in 30 c.e. Between 1911 and 1917, Samuel J. Crowe, professor of otolaryngology at Johns Hopkins, reviewed one thousand tonsillectomies performed. His description of sharp dissection with low incidence of complications opened the way to common use of this procedure. By the middle part of the twentieth century, there were more than two million tonsillectomies being performed every year in the United States. Between 1915 and 1960, tonsillectomy and adenoidectomy was the most frequently performed surgery in the United States. Today that number has dropped to about 600,000 cases per year in the United States, according to the American Academy of Otolaryngology. The introduction of new techniques such as electrocautery, laser surgery, and high-frequency ablation have further contributed to lowering the complication rate associated with tonsillectomy to the point that about 80 percent of procedures are now done as outpatient surgery.

Recent research regarding cancers of the oral cavity including squamous cell tonsillar cancers has centered on the emerging role of HPV. HPV is one of the most common viruses in the world. In most cases, these viruses are relatively harmless. However, sexually transmitted types HPV 16 and 18 have been strongly linked to cervical cancer, and they are increasingly being recognized as a cause of oral cancer as well. Smoking and drinking alcohol may promote the invasive ability of these viruses in the oral cavity. Recent studies suggest that as many as 25 percent of oral cancers may be positive for HPV. Some studies suggest that HPV-positive oral cancers have a better prognosis than HPV-negative cancers. Another recent study suggests that HPV-positive tumors are more likely to begin within the tonsillar crypts. Understanding the relationship and effect of HPV on tonsil cancer may lead to novel approaches for prevention, targeted therapy, and improved ability to predict the prognosis of these tumors.


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