Mast cells
Mast cells are - like macrophages, lymphocytes and
eosinophils - in demand when something goes wrong in the connective tissue.
Quite a few of them are present in healthy connective tissue as they stand on
guard and monitor the local situation. The cytoplasm of mast cells is filled by
numerous large vesicles. Mast cells discharge the contents of these vesicles if
they come in contact with antigens, for example, proteins on the surface of an
invading bacterium or, in allergic reactions, in response to antigens found,
for example, on the surface of pollen grains.
The most prominent substances contained in the
vesicles are heparin and histamine. They increase
blood flow in close by vessels and the permeability of the vessel walls to
plasma constituents and other white blood cells. By facilitating access to the
area, mast cells facilitate an immune response to the antigen which triggered
the release histamine and heparin.
Other
connective tissue cells
Lymphocytes
and plasma cells
Lymphocytes are usually small
cells (6 - 8 µm). Their nuclei are round and stain very dark. The cytoplasm
forms a narrow rim around the nucleus and may be difficult to see. There are
many of them in the connective tissue underlying the epithelia of the
gastrointestinal tract but usually much fewer in other connective tissues.
Again, this situation may change - in this case with immunological reactions.
Some lymphocytes may differentiate into plasma cells. Plasma cells are
lymphocytes which produce antibodies. To accommodate the necessary organelles
for this function the size of the cytoplasm increases dramatically and the
cells become basophilic. Plasma cells can occasionally be spotted in the loose
connective tissue present in sections.
Like eosinophilic cells and monocytes, lymphocytes are white blood cells.
Eosinophilic
cells
Eosinophilic cells are typically
rounded or oval, large cells, which contain large amounts of bright red
granules in their cytoplasm. They originate, like the monocytes, in the bone
marrow. They enter connective tissues early in inflammatory reactions, where
they phagocytose antigen-antibody complexes. Their numbers in healthy
connective tissue vary with location, but a few of them can usually be found.
Mesenchymal
cells
During development, mesenchymal cells give rise to other cell types of the
connective tissue. A small number of them may persist into adulthood.
Mesenchymal cells are smaller than fibrocytes and difficult to detect in
histological sections. They may regenerate blood vessels or smooth muscle which
have been lost as a consequence of tissue damage.
sections
of tongue, skin, mesentery
or other sections containing epithelia and / or loose connective tissue - toluidine blue, cresyl violet
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Mast Cells, Tongue - toluidine blue and
Mesentry, Rat - cresyl violet
Mast cells are relatively frequent in the connective tissue benath the
epithelium and between the muscle fibres of the tongue. In most connective
tissue cells and the muscle fibres only the nucleus is stained by the
toluidine blue. The cytoplasm of the mast cells is however filled with dark,
blue / violet grains which represent their secretory vesicles. At low
magnification mast cells stand out as large, dark dots among smaller and
lighter stained nuclei and among the very weakly stained remaining connective
tissue components.
Draw a few mast cells in situ and label both the mast cells
and some of the surrounding tissue components.
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![thumbnail]( "Mast cells are")
Title:
Mast cells are
by:
om
at
2013-02-15T02:53:00+07:00
Rating: 4.8
of 5 Reviews
Mast cells are