reign substances.
Resident macrophages normally remain at rest (rather than circulating in and out of tissues like the lymphocytes). But the normal number of fixed macrophages is supplemented during inflammation by the influx of many monocytes from the blood. When faced with a target too big for one cell, a splinter for example, several macrophages may fuse together for a single huge multinucleate mass called a "foreign body giant cell."
Monocytes are the largest of the leukocytes, and constitute about 5% of the white blood cell population. Their nuclei are typically indented, with a kidney-bean shape, in blood smears. Tissue macrophages are diverse in appearance and not easily distinguished from the more common fibroblasts. Macrophages are generally larger, and may contain brown pigment granules which represent indigestible residue in tertiary lysosomes. In electron micrographs macrophages are generally recognized by the presence of numerous lysosomes of various sizes, including large heterophagic vesicles.
[More on blood cells.]
For more about the immune system, including outside links, see CRR Lymphatic System.
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EXAMPLES of inflammation
Microscopically, inflammation shows up most clearly as increased numbers of white blood cells (i.e., the inflammatory infiltrate which results from emigration of leukocytes).
Images of inflammatory infiltrate in skin.
The WebPath website offers a number of illustrative examples of inflammation, including:
- cholecycitis (inflammation of the gall bladder)
- endometritis (inflammation of the lining of the uterus)
- cervicitis (inflammation of the cervix)
- rheumatoid arthritis (inflammation of joints)
- pneumonia (inflammatory exudate in lung); abscessing pneumonia
- influenza (interstitial inflammation of lung)
- more from WebPath
Also see specimens at Virtual Slidebox of Histopathology, University of Iowa Department of Pathology.
Online slides of cell injury, inflammation, and repair
Note that appreciating inflamed tissue samples, such as those listed above, calls for some prior familiarity with normal histological appearance.
For more about the immune system, see outside links and CRR Lymphatic System.
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SIUC / School
of Medicine / Anatomy / David
Last updated: 1 January 2013 / dgk