The human

palatine tonsils 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 ...

(PT) are covered by

stratified squamous epithelium A stratified squamous epithelium consists of squamous (flattened) epithelial cells arranged in layers upon a basal membrane. Only one layer is in contact with the basement membrane; the other layers adhere to one another to maintain structural i ...

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 Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellula ...

surface area of the crypts is 295 cm², in addition to the 45 cm² of epithelium covering the

oropharyngeal The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its struct ...

surface. The crypts extend through the full thickness of the tonsil reaching almost to its hemicapsule. In healthy tonsils the openings of the crypts are fissure-like, and the walls of the

lumina Lumina may refer to: Arts, entertainment, and media Literature * ''Lumina'', a literary journal published by Sarah Lawrence College * ''World of Lumina'' or ''Lumina'', a graphic novel by Emanuele Tenderini and Linda Cavallini Music * "Lumina", ...

are in apposition. A computerized three-dimensional reconstruction of the palatine tonsil crypt system showed that in the centre of the palatine tonsil are tightly packed ramified crypts that join with each other, while on the periphery there is a rather simple and sparse arrangement. The crypt system is not merely a group of

invagination Invagination is the process of a surface folding in on itself to form a cavity, pouch or tube. In developmental biology, invagination is a mechanism that takes place during gastrulation. This mechanism or cell movement happens mostly in the vegetal ...

s of the tonsillar epithelium but a highly complicated network of canals with special types of epithelium and with various structures surrounding the canals, such as blood and lymphatic vessels and germinal centers.

Macrophages Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer ce ...

and other

white blood cells White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...

concentrate by the tonsillar crypts as well, in response to the microorganisms attracted to the crypts. Accordingly, the tonsillar crypts serve a forward sentry role for the

immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...

, by providing early exposure of immune system cells to infectious organisms which may be introduced into the body via food or other ingested matter. However, the tonsillar crypts often provide such an inviting environment to

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

that bacterial colonies may form solidified "plugs" or "stones" within the crypts. In particular, sufferers of chronic

sinusitis Sinusitis, also known as rhinosinusitis, is inflammation of the nasal mucosa, mucous membranes that line the paranasal sinuses, sinuses resulting in symptoms that may include thick Mucus#Respiratory system, nasal mucus, a nasal congestion, plugg ...

post-nasal drip Post-nasal drip (PND), also known as upper airway cough syndrome (UACS), occurs when excessive mucus is produced by the nasal mucosa. The excess mucus accumulates in the back of the nose, and eventually in the throat once it drips down the back of ...

frequently suffer from these overgrowths of bacteria in the tonsillar crypts. These small whitish plugs, termed "

tonsilloliths 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. Generall ...

" and sometimes known as "tonsil stones," have a foul smell and can contribute to

bad breath Bad breath, also known as halitosis, is a symptom in which a noticeably unpleasant breath odour is present. It can result in anxiety among those affected. It is also associated with depression and symptoms of obsessive compulsive disorder. Th ...

; furthermore, they can obstruct the normal flow of

pus Pus is an exudate, typically white-yellow, yellow, or yellow-brown, formed at the site of inflammation during bacterial or fungal infection. An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collection ...

from the crypts, and may irritate the throat (people with tonsil stones may complain of the feeling that something is stuck in their throat).

References

{{Authority control Lymphatics of the head and neck Tonsil