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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 mucosal immune system consists of a cellular component, humoral immunity, and defense mechanisms that prevent the invasion of microorganisms and harmful foreign substances into the body. These defense mechanisms can be divided into physical barriers ( epithelial lining , mucus , cilia function , intestinal peristalsis , etc.) and chemical ...
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 innate immune system is an alternate defense strategy and is the dominant immune system response found in plants, fungi, prokaryotes, and invertebrates (see Beyond vertebrates). [ 2 ] The major functions of the innate immune system are to:
The mononuclear phagocyte system is part of both humoral and cell-mediated immunity. The mononuclear phagocyte system has an important role in defense against microorganisms, including mycobacteria, fungi, bacteria, protozoa, and viruses. Macrophages remove senescent erythrocytes, leukocytes, and megakaryocytes by phagocytosis and digestion.
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.
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.