The body has a variety of defense mechanisms that protect against injury & infection
These defenses are
the skin & mucous membranes (primary line of defense)
the mononuclear phagocyte system
the inflammatory response
the immune system Lemone 295-303
Mononuclear phagocyte system (MPS)
It is not a body system with particular tissues & organs
It consists of free (mobile) or fixed phagocytic cells
The macrophages of the liver, spleen, bone marrow, lungs, lymph nodes, & N.S. are all fixed phagocytes
The monocytes are in the blood and the macrophages in the connective tissue "histocytes" - mobile or wandering phagocytes
Monocytes & macrophages stem from bone marrow
Monocytes spend a couple of days in the blood & penetrate tissues & change into macrophages
Tissue macrophages are larger & more phagocytic than monocytes
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