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Concept
Tonsille pharyngienne
Résumé
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.
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