OVERVIEW of Connective Tissue
Connective tissue forms a framework upon which epithelial tissue rests and within which nerve tissue and muscle tissue are embedded. Blood vessels and nerves travel through connective tissue.
Connective tissue functions not only as a mechanical support for other tissues but also as an avenue for communication and transport among other tissues. Most significantly, connective tissue is the stage for inflammation. The principal cell types involved in immunological defense are found within connective tissue
Connective tissue is derived from embryonic mesenchyme (unlike most epithelial tissue which is derived from ectoderm and endoderm).
Connective tissue consists of individual cells scattered within an extracellular matrix. Unlike cells of epithelial tissue, connective tissue cells are not directly attached to one another. Individual connective tissue cells are normally separated from one another by varying amounts of extracellular matrix. CELLS: The most common connective tissue cells are:
Fibroblasts, which secrete collagen and other elements of the extracellular matrix. Adipocytes, which store fat.
Mast cells, macrophages, and lymphocytes, cells with immune function which participate in inflammation. MATRIX: Connective tissue matrix is composed of: ground substance and fibers.
In ordinary connective tissue, the ground substance consists of water stabilized by glycosaminoglycans, proteoglycans, and glycoproteins. In bone the ground substance includes minerals.
In blood, the ground substance is fluid (plasma).
The principal fiber type is collagen -- the most abundant protein in the body -- which confers tensile strength with flexibility. Elastic fibers confer resiliency.
The matrix is produced by fibroblasts (or related cell types -- chondroblasts in cartilage and osteoblasts in bone).
Connective tissue assumes widely varying forms, embracing not only many variations on...
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