Page 170 - Atlas of Histology with Functional Correlations

are exposed to antigens. Thus, plasma cells become mature cells highly

specialized for antibody (immunoglobulin) synthesis that is released into
the blood stream to destroy specific antigens and defend the organism against
infections.

Adipose cells store fat (lipid) and are mostly found in loose connective
tissue. There are white adipose cells and brown adipose cells. Their main

function is to provide protective packing material and insulation in and
around numerous vital organs. Additional information concerning both types
of adipose cells and a histological image of adipose tissue are provided in
Functional Correlations Box 5.4 and in Figure 5.13.

Neutrophils are active and powerful phagocytes; they leave the
bloodstream and enter connective tissue to engulf and destroy bacteria at
sites of infections.

Eosinophils become activated and increase in number after parasitic
infections or allergic reactions. They phagocytize antigen–antibody

complexes formed during allergic reactions.

Mast cells reside in the connective tissue. Their location near small
blood vessels and capillaries allows them to perform numerous defensive
functions. The cytoplasm of mast cells contains numerous dense-staining

granules, which upon release function in local inflammatory and immune
responses. Exposure of mast cells to allergens causes rapid release of
histamine and other vasoactive mediators. Histamine causes dilation of
blood vessels and increases the permeability of capillaries and venules,
thereby causing local edema. Release of histamine also induces symptoms of

allergic reactions known as immediate hypersensitive reactions. Mast cells
also contain the chemical heparin, which acts locally as a weak
anticoagulant.

FIBROUS COMPONENTS OF THE

CONNECTIVE TISSUE

There are three distinctive types of connective tissue fibers: collagen, elastic,
and reticular. The amount and arrangement of these fibers depend on the

function of the tissues or organs in which they are found. Fibroblasts synthesize

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