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In the first line of defense, inhaled bacteria are trapped by mucus and are swept toward the pharynx and are swallowed. [1] Bacteria which penetrate the mucous layer are dealt with a second line of defense which includes antimicrobial peptides that are secreted by the surface epithelium of the respiratory tract which kill many strains of ...
The second and third lines of defense operate by making changes to the buffers, each of which consists of two components: a weak acid and its conjugate base. [ 5 ] [ 13 ] It is the ratio concentration of the weak acid to its conjugate base that determines the pH of the solution. [ 14 ]
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 (or pharyngeal tonsil), two tubal tonsils, two palatine tonsils, and the lingual tonsils.
The cells in the respiratory epithelium are of five main types: a) ciliated cells, b) goblet cells, c) brush cells, d) airway basal cells, and e) small granule cells (NDES) [6] Goblet cells become increasingly fewer further down the respiratory tree until they are absent in the terminal bronchioles; club cells take over their role to some extent here. [7]
Innate immune system cells prevent free growth of microorganisms within the body, but many pathogens have evolved mechanisms to evade it. [ 21 ] [ 22 ] One strategy is intracellular replication, as practised by Mycobacterium tuberculosis , or wearing a protective capsule, which prevents lysis by complement and by phagocytes, as in Salmonella ...
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An immune response is a physiological reaction which occurs within an organism in the context of inflammation for the purpose of defending against exogenous factors. These include a wide variety of different toxins, viruses, intra- and extracellular bacteria, protozoa, helminths, and fungi which could cause serious problems to the health of the host organism if not cleared from the body.
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