Acute inflammation Acute inflammation is marked by an increase
in inflammatory cells. Perhaps the simplest indicator of acute
inflammation is an increase in the white blood cell count in the
peripheal blood, here marked by an increase in segmented
neutrophils (PMN's).
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Inflammatory process. Selectins: molecules on leukocytes
(L-selectin) and endothelium (E-selectin, P-selectin) act as
receptors to provide loose binding for rolling. ICAM-1:
intercellular adhesion molecule 1 provides more firm adhesion of
the neutrophil, via integrins on neutrophil surfaces, to the
endothelium. CD31: this cell to cell adhesion molecule aids in
diapedesis. C5a and LTB4: chemotaxis is aided by the C5a component
from complement activation, along with leukotriene B4, a product of
the lipo-oxygenase pathway of arachidonic acid metabolism.
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Inflammatory process conts. C3b and IgG: opsonins such as the
C3b component from complement activation, as well as immunoglobulin
G, coat foreign objects such as bacteria to aid in phagocytosis by
binding to leukocyte receptors. Myeloperoxidase, lysozyme: after
engulfment, killing of bacteria occurs via generation of toxic
oxygen species (superoxide) converted to hydrogen peroxide and
further converted to a hypochlorous radical by myeloperoxidase from
neutrophil granules. In the absence of oxidation, lysozyme from
neutrophil granules can form holes in microbial membranes.
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Acute appendicitis. This is a photomicrograph of an appendix
exhibiting acute inflammation. Note that there are only remnants of
mucosal tissue identifiable along the luminal border of this
specimen. Note that the surface is very roughened and has deposits
of fibrin. The blue color is due to the presence of many
inflammatory cells, although at this low power these individual
cells cannot be specifically identified.
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Identif the organ? What is the pathology here?
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Lobar pneumonia. This is a gross photograph of the lungs from a
patient (not the patient from this case) with acute lobar
pneumonia. The lung lobe in the upper-right portion of the
photograph is affected withpneumonia (arrows)
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Lobar pneumonia. This is a cut section of a lung from the
preceding image. Note the whitish discoloration of the lung tissue
in the upper lobe (arrows) compared to the normal collapsed and
pink staining lung lobe in the left-hand portion of the photograph.
The white discoloration in this tissue is due to infiltration of
leukocytes (primarily neutrophils). Note that only one lobe of the
lung is involved in this patient with lobar pneumonia.
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Lobar pneumonia. This is a photomicrograph of alveoli filled
with exudate. The alveolar wall outlines (arrows) are barely
visible in this section. The alveoli are filled with PMNs, fibrin,
and edema fluid. This is a severe acute inflammatory response but
the structure of the alveoli remains intact. This tissue is able,
with proper treatment, to completely resolve this inflammatory
response. Since there has not been necrosis of the lung tissue
itself (loss of tissue), this lung could completely recover normal
function (resolution).
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X-ray image of Lobar pneumonia.
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Chronic cervicitis. Here is chronic cervicitis. Prolonged acute
inflammation or repeated bouts of acute inflammation may lead to
the appearance of more mononuclear cells, and chronic inflammation.
In this case the inflammation is severe enough to produce mucosal
damage with hemorrhage
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Granulation tissue. Healing of inflammation often involves
ingrowth of capillaries and fibroblasts. This forms granulation
tissue. Here, an acute myocardial infarction is seen healing. There
are numerous capillaries, and collagen is being laid down to form a
scar. Non-infarcted myocardium is present at the far left.
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What are the components of a granulation tissue.
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Granulation tissue. At high magnification, granulation tissue
has capillaries, fibroblasts, and a variable amount of inflammatory
cells (mostly mononuclear, but with the possibility of some PMN's
still being present).
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Identify the slide.
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Granulation tissue after skin biopsy This is a healing biopsy
site on the skin seen a week following the excision, The skin
surface has re- epithelialized, and below this is granulation
tissue with small capillaries and fibroblasts forming collagen.
After a month, just a small collagenous scar will remain.
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Identify the organ? What is the pathology here?
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Caseating granuloma. Grossly, a granuloma tends to be a focal
lesion. Seen here in a hilar lymph node is a granuloma. Granulomas
due to infectious agents such as mycobacteria are often described
as "caseating" when they have prominent caseous necrosis.
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Caseating granuloma. This is a caseating granuloma. Epithelioid
cells surround a central area of necrosis that appears irregular,
amorphous, and pink. Grossly, areas of caseation appear
cheese-like.
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Granulomas. The focal nature of granulomatous inflammation is
demonstrated in this microscopic section of lung in which there are
scattered granulomas in the parenchyma. This is why the chest
radiograph with tuberculosis or other granulomatous diseases is
often described as "reticulonodular".
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Pulmonary granulomas Here are two pulmonary granulomas.
Granulomatous inflammation typically consists of mixtures of cells
including epithelioid macrophages, giant cells, lymphocytes, plasma
cells, and fibroblasts. There may even be some neutrophils.
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Langhans type giant cells A giant cell is a mass formed by the
union of several distinct cells (usually macrophages), often
forming Granuloma. Seen here are two Langhans type giant cells in
which the nuclei are lined up around the periphery of the cell.
Additional pink epithelioid macrophages compose most of the rest of
the granuloma