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Macrophages in the Lymph Nodes
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Macrophages in the Lymph Nodes

Essentially no particulate matter that enters the tissues, such as bacteria, can be absorbed directly through the capillary membranes into the blood. Instead, if the particles are not destroyed locally in the tissues, they enter the lymph and flow to the lymph nodes located intermittently along the course of the lymph flow. The foreign particles are then trapped in these nodes in a meshwork of sinuses lined by tissue macrophages.

Function of lymph nodes

1 Filtration: Removal of foreign particles e.g. carbon particles.      

2 Removal of bacteria: The lymph nodes enlarge (macrophages increase mucn in number). They are the defence mechanism against local infection.

3 Formation of lymphocytes and plasma cells: which leave the nodes through the efferent lymph vessels to reach the blood stream.

4 Production of antibodies: by lymphocytes as a defence mechanism.

Liver:

Bacteria pass through gastrointestinal mucosa ®portal blood  phagocytosis by kupffer cells lining blood sinuses of the liver and no I bacteria pass to systemic circulation.

Macrophages (Kupffer Cells) in the Liver Sinusoids

Still another favorite route by which bacteria invade the body is through the gastrointestinal tract. Large numbers of bacteria from ingested food constantly pass through the gastrointestinal mucosa into the portal blood. Before this blood enters the general circulation, it passes through the sinusoids of the liver; these sinusoids are lined with tissue macrophages called Kupffer cells, shown in Figure 4.5. These cells form such an effective particulate filtration system that almost none of the bacteria from the gastrointestinal tract succeeds in passing from the portal blood into the general systemic circulation. Indeed, motion pictures of phagocytosis by Kupffer cells have demonstrated phagocytosis of a single bacterium in less than 1/100 of a second.

 

Figure 4.5 – Kupffer cells lining the liver sinusoids, showing phagocytosis of India ink particles into the cytoplasm of the Kupffer cells.



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