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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.
A scanning electron microscope image of a single neutrophil (yellow/right), engulfing anthrax bacteria (orange/left) – scale bar is 5 μm (false color). The immune system is a network of biological systems that protects an organism from diseases.
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The second group is the non-phagocytic types that are distributed near regenerative fibers. These peak between two and four days and remain elevated for several days while muscle tissue is rebuilding. [60] The first subpopulation has no direct benefit to repairing muscle, while the second non-phagocytic group does.
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The glia limitans also acts as a second line of defense against anything that passes the blood–brain barrier. However, because the astrocytes surrounding the vessels are connected by gap junctions, it is not considered part of the BBB and material can readily pass between the foot processes.