Anatomy Head and neck Pharynx

Tonsils

Author: Shahab Shahid MBBS • Reviewer: Uruj Zehra MBBS, MPhil, PhD
Last reviewed: February 22, 2023
Reading time: 7 minutes

The tonsils are masses of lymphoid tissue and form an important part of our immune system located at the gateway of the respiratory and digestive tracts. They act as the first line of defense against ingested or inhaled pathogens. Four types of tonsils are arranged into a ring around the pharynx (oropharynx and nasopharynx), known as Waldeyer’s ring of lymphoid tissue.

This article will look at the anatomy of the tonsils including the blood supply and innervation, as well as some histological anatomy and embryological development. We will also discuss function and clinical relevance.

Contents

Anatomy
1. Development
2. Histology
Types of tonsils
Clinical points
1. Tonsillitis
2. Tonsillectomy
Sources

+ Show all

Anatomy

Development

The tonsils are part of MALT (mucosa associated lymphoid tissue). MALT can also be found in the bowel, in Peyer’s patches. In general MALT is relatively undeveloped at birth with low cellularity. Tonsils start to develop around 14-15th week of embryonic life, while germinal centres are absent at this stage. Palatine tonsils and tonsillar fossa are believed to be the derivatives of the 2nd pharyngeal pouch. The epithelial lining proliferates and forms buds, which form the primordium of the palatine tonsil.

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Histology

Microscopically, the tonsil is a mass of lymphoid follicles supported on a connective tissue framework. In addition, the center of each of these nodules is densely packed with lymphocytes, and is referred to as the germinal center. The tonsillar crypts (except the pharyngeal tonsil) will penetrate from the surface, almost down to the very center of the tonsil follicle. The luminal surfaces of the tonsils are coated in non-keratinizing stratified squamous epithelium, which is the same tissue of the surrounding oropharynx.

They have antigen presenting cells on their surface that alert the underlying B and T cells, which are part of the adaptive immune response. In addition, the B cells produce antibodies, mainly IgA, which act to provide immune protection on mucosal surfaces.

Learn everything about the structure and function of lymphoid tissue with our articles, video tutorials, quizzes, and diagrams.

Types of tonsils

There are four types of tonsils in humans; palatine, pharyngeal, lingual and tubal. To quickly remember this, you can use the following mnemonic: "PPL have Tonsils", standing for Palatine, Pharyngeal, Lingual, Tubal.

Palatine tonsils

These are located between the palatoglossal arch anteriorly and the palatopharyngeal arch posteriorly. They are located in the isthmus of the fauces (a cavity bound laterally by the palatoglossal arches, superiorly by the soft palate and by the tongue underneath). Laterally they are attached to the wall by a fibrous capsule, and are covered in stratified squamous epithelium on the pharyngeal side. The tonsil is penetrated by 15-20 crypts. The lumen of the crypts contain lymphocytes, bacteria and desquamated epithelial cells.

The palatine tonsils receive their blood supply from the tonsillar branches of five arteries:

Ascending palatine branch of the facial artery
Tonsillar branch of the facial artery
Ascending pharyngeal branch of the external carotid
Dorsal lingual branch of the lingual artery
Lesser palatine branch of the descending palatine artery

Venous drainage is to the internal jugular vein via the peritonsillar plexus of lingual and pharyngeal veins.

The nerve supply to the palatine tonsils arises from the maxillary division (V2 division) of the trigeminal nerve (cranial nerve V) as well as the tonsillar branches of the glossopharyngeal nerve (cranial nerve IX). The glossopharyngeal nerve will also continue on to supply taste to the posterior one third of the tongue as well as sensation.

Lingual tonsils

These are small round elevations that sit on the most posterior part of the tongue base. They are considered a collection of lymphoid tissue which varies greatly in size and shape. They are covered by stratified squamous epithelium which invaginates to form a single crypt.

The blood supply to these tonsils is from the lingual artery, the tonsillar branch of the facial artery and the ascending pharyngeal branch of the external carotid artery.

The nerve supply is from the tonsillar branches of the glossopharyngeal nerve (cranial nerve IX).

Tubal tonsils

These tonsils are located just posterior to the opening of the Eustachian tube (the torus tubaris) in the nasopharynx.

Pharyngeal tonsil/adenoid

This is the most superior tonsil that lies in the superior part of the nasopharynx. It is attached to the periosteum of the sphenoid bone by connective tissue. The pharyngeal tonsil is covered with ciliated pseudostratified columnar epithelium, having ciliated, basal and goblet cells.

The covering capsule is thinner compared to the palatine tonsils and the adenoids have no crypts. The epithelium is thrown into folds, with the lamina propria containing a mass of lymphatic tissue with numerous lymphatic nodules.

Ready to round up and reinforce your lymphatic system knowledge? Try out our quiz below:

Clinical points

Tonsillitis

This inflammatory condition of the tonsils is due to viral or bacterial infections. It presents with:

Throat infection
Fever
Hoarseness or loss of voice
Issues with swallowing
A visible white or yellow coating on the tonsils upon examination.

Treatment includes painkillers, as well as antibiotics (for immunocompromised, severe or painful cases only). Recurrent tonsillitis is defined as 4-7 infections a year. In case of recurrent, persistent and enlarged tonsils problems, surgical removal is recommended.

Tonsillectomy

This is a surgical procedure where the palatine tonsils are removed from each side of the oropharynx. The surgery is usually needed due to:

Airway obstruction from enlarged tonsils
Sleep apnoea
Snoring
Recurrent tonsillitis

Other tonsils can also be removed in the same procedure. As the tonsils are highly vascularised, they bleed heavily during the surgery. Hydration and analgesics are essential for good recovery.

Sources

All content published on Kenhub is reviewed by medical and anatomy experts. The information we provide is grounded on academic literature and peer-reviewed research. Kenhub does not provide medical advice. You can learn more about our content creation and review standards by reading our content quality guidelines.

References:

Frank H.Netter MD: Atlas of Human Anatomy, 5th Edition, Elsevier Saunders.
Chummy S.Sinnatamby: Last’s Anatomy Regional and Applied, 12th Edition, Churchill Livingstone Elsevier.
Richard L. Drake, A. Wayne Vogl, Adam. W.M. Mitchell: Gray’s Anatomy for Students, 2nd Edition, Churchill Livingstone Elsevier.
Viswanatha B, DO, MBBS, PhD, MS, FACS: Tonsil and Adenoid Anatomy. WebMD LLC (accessed 17/01/2016).

Illustrators:

Tonsillar crypt (medial view) - Begoña Rodriguez
Palatine tonsil (ventral view) - Paul Kim
Lingual tonsil (cranial view) - Begoña Rodriguez
Pharyngeal tonsil (medial view) - Yousun Koh

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