Extracellular matrix

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In biology, extracellular matrix (ECM) is any material part of a tissue that is not part of any cell. Extracellular matrix is the defining feature of connective tissue.

ECMs main components are various glycoproteins, proteoglycans and hyaluronic acid. In most animals, the most abundant glycoproteins in the ECM are collagens. ECM also contains many other components: proteins such as fibrin, elastin, fibronectins, laminins, and nidogens, and minerals such as hydroxylapatite, or fluids such as blood plasma or serum with secreted free flowing antigens. In addition it sequesters a wide range of cellular growth factors, and acts as a local depot for them. Changes in physiological conditions can trigger protease activities that cause local release of such depots. This allows the rapid and local activation of cellular functions, without de novo synthesis.

Given this diversity, ECM can serve many functions, such as providing support and anchorage for cells, providing a way of separating the tissues, and regulating intercellular communication. The ECM regulates a cell's dynamic behavior.

Many cells bind to components of the extracellular matrix. This cell-to-ECM adhesion is regulated by specific cell surface cellular adhesion molecules (CAM) known as integrins. The integrins transmit mechanical stimuli from the ECM to the cytoskeleton.

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