Forensic Pathology for Police - Brainshare Public Online Library

114 6 Overview of Anatomy and Physiology
Fig. 6.24 Histology section of bone marrow. Note the bony trabeculae (large scaffolding-like
structures) surrounded by bone marrow cells and fat (clear cells)
travels through the lungs, and it is released to other tissues when the blood travels
through the capillaries of those tissues. A unique feature of rbcs is that they
contain no nucleus, although during development within the bone marrow, the rbc
precursor cells do have nuclei. Red blood cells only live for approximately 120 days
before they become “worn out” so new rbc production is a constant requirement.
Old rbcs are removed by the spleen and other mechanisms. Hemoglobin from the
destroyed rbcs is broken-down in the liver and incorporated into bile. Hemoglobin
can be evaluated, even in postmortem samples, via a process known as “hemoglobin
electrophoresis.”
White blood cells are important in the processes of inflammation and immune
reactions. The wbcs circulate within the blood and are actually able to leave the
blood and enter other tissues where inflammation or an immune reaction has been
initiated. Depending on the underlying reason for the inflammation, different types
of wbcs may accumulate. In general, neutrophils (PMNs) tend to accumulate in
response to bacterial infections or tissue necrosis (cell death in an otherwise living
tissue). Neutrophilic inflammation is sometimes called suppurative inflammation.
Grossly, a collection of suppurative inflammation may have the appearance of pus
and can also be called purulent inflammation. A localized collection of neutrophilic
inflammation in association with tissue necrosis is called an abscess. Lymphocytes
accumulate in response to viral infections or chronic (longterm) inflammation.
Macrophages (which begin as blood monocytes) accumulate in response to a variety
of chronic infections or inflammatory processes, including the presence of foreign
substances. A localized collection of macrophages associated with lymphocytes is
referred to as a granuloma. Granulomatous inflammation is characteristic of several
disease processes, including tuberculosis. Eosinophils accumulate in a variety of
situations, including allergic reactions and parasite infections. Figure 1.2 shows the
microscopic appearance of several types of blood cells.