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Connective and supportive 3

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tissues (textus connectivus)

Connective and supportive tissues include a structurally Cells
and functionally diverse range of tissues that, except for The cells of the connective and supportive tissues are
the ectodermally derived connective tissue of the rostral derived from embryonic mesenchymal cells. Through
head, originate from mesoderm. Thus, they are never their multiple processes, these cells form a loose, predom-
located on the surface of the body. Connective and sup- inantly three-dimensional network. Their oval nucleus
portive tissues are integral in forming the framework contains little heterochromatin.
of the body and the structure of organs. They perform Embryonic mesenchymal cells are pluripotent, capa-
mechanical and supportive roles, and participate actively ble of differentiating into either resident cells (cells that
in the exchange of substances between the vascular system remain fixed within connective and supportive tissue) or
and specific tissues. Connective tissue is also involved in transient or wandering cells (cells that enter the tissue in
cellular and humoral defence mechanisms, and contributes response to particular stimuli).
to thermoregulation and hydroregulation. Several connec-
tive tissues permanently retain their mesodermally derived Resident cells
capacity for regeneration and transformation. Resident cells of connective tissue include fibroblasts and
adipocytes. Connective tissue macrophages (histiocytes)
Structure of connective and supportive and mast cells are also fixed residents of connective tis-
tissues sue. However, as these are derived from the blood, they
Morphologically, connective and supportive tissues consist are considered in some classification systems to be wan-
of: dering (‘free’) cells. Chondroblasts and osteoblasts are
permanent residents of the supportive tissues, cartilage and
bone.
· cells and
· intercellular matrix. Fibroblasts, chondroblasts and osteoblasts produce
fibres, cartilage and bone, respectively, before differentiat-

3.1 Scanning electron micrograph of a macrophage isolated from peritoneal fluid (x1000).

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