Download A fibroblast is a type of cell that synthesizes the extracellular matrix

A fibroblast is a type of cell that synthesizes the extracellular matrix and
collagen (and fibrin), the structural framework (stroma) for animal tissues, and
play a critical role in wound healing. They are the most common cells of
connective tissue in animals.
Fibroblasts and fibrocytes are two states of the same cells, the former being the
activated state, the latter the less active state, concerned with maintenance.
Currently, there is a tendency to call both forms fibroblasts. The suffix "blast" is
used in cellular biology to denote a stem cell or a cell in an activated state of
metabolism.
The main function of fibroblasts is to maintain the structural integrity of
connective tissues by continuously secreting precursors of the extracellular
matrix. Fibroblasts secrete the precursors of all the components of the
extracellular matrix, primarily the ground substance and a variety of fibres. The
composition of the extracellular matrix determines the physical properties of
connective tissues.
Fibroblasts are morphologically heterogeneous with diverse appearances
depending on their location and activity. Though morphologically inconspicuous,
ectopically transplanted fibroblasts can often retain positional memory of the
location and tissue context where they had previously resided, at least over a
few generations.
Unlike the epithelial cells lining the body structures, fibroblasts do not form flat
monolayers and are not restricted by a polarizing attachment to a basal lamina
on one side, although they may contribute to basal lamina components in some
situations (eg subepithelial myofibroblasts in intestine may secrete the α-2 chain
carrying component of the laminin which is absent only in regions of follicle
associated epithelia which lack the myofibroblast lining). Fibroblasts can also
migrate slowly over substratum as individual cells, again in contrast to epithelial
Structure and function
Fibroblasts have a branched cytoplasm surrounding an elliptical, speckled
nucleus having one or two nucleoli. Active fibroblasts can be recognized by their
abundant rough endoplasmic reticulum. Inactive fibroblasts, which are also called
fibrocytes, are smaller and spindle shaped. They have a reduced rough
endoplasmic reticulum. Although disjointed and scattered when they have to
cover a large space, fibroblasts when crowded often locally align in parallel
clusters.
Fibroblasts make collagens, glycosaminoglycans, reticular and elastic fibers, and
glycoproteins found in the extracellular matrix. Growing individuals' fibroblasts
are dividing and synthesizing ground substance. Tissue damage stimulates
fibrocytes and induces the mitosis of fibroblasts.