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Concept
Adenoid
Summary
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.
The term adenoid is also used to represent adenoid hypertrophy, the abnormal growth of the pharyngeal tonsils.
The adenoid is a mass of lymphatic tissue located behind the nasal cavity, in the roof of the nasopharynx, where the nose blends into the throat. The adenoid, unlike the palatine tonsils, has pseudostratified epithelium. The adenoids are part of the so-called Waldeyer ring of lymphoid tissue which also includes the palatine tonsils, the lingual tonsils and the tubal tonsils.
Adenoids develop from a subepithelial infiltration of lymphocytes after the 16th week of embryonic life. After birth, enlargement begins and continues until aged 5 to 7 years.
Part of the immune system, adenoids trap and recognize pathogens such as bacteria and viruses. In response, the adenoid produces T cells and B cells to combat infection, contributing to the sythesis of IgA immunoglobulins, assisting in the body's immunologic memory.
Species of bacteria such as lactobacilli, anaerobic streptococci, actinomycosis, Fusobacterium species, and Nocardia are normally present by 6 months of age. Normal flora found in the adenoid consists of alpha-hemolytic streptococci and enterococci, Corynebacterium species, coagulase-negative staphylococci, Neisseria species, Haemophilus species, Micrococcus species, and Stomatococcus species.
An enlarged adenoid, or adenoid hypertrophy, can become nearly the size of a ping pong ball and completely block airflow through the nasal passages. Even if the enlarged adenoid is not substantial enough to physically block the back of the nose, it can obstruct airflow enough so that breathing through the nose requires an uncomfortable amount of work, and inhalation occurs instead through an open mouth.
Official source
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Ontological neighbourhood
Related publications (2)
Zebrafish gcm2 is required for gill filament budding from pharyngeal ectoderm
The pharyngeal arches give rise to multiple organs critical for diverse processes, including the thymus, thyroid and parathyroids. Several molecular regulators of thymus and thyroid organogenesis are strikingly conserved between mammals and zebrafish. Howe ...
2004Related concepts (7)
Pharynx
The pharynx (: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the esophagus and trachea (the tubes going down to the stomach and the lungs respectively). It is found in vertebrates and invertebrates, though its structure varies across species. The pharynx carries food to the esophagus and air to the larynx. The flap of cartilage called the epiglottis stops food from entering the larynx. In humans, the pharynx is part of the digestive system and the conducting zone of the respiratory system.
Tonsil
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.
Tonsillectomy
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 (95% confidence interval: 1.0 to 0.1) 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.