The Extracellular Matrix (ECM) is a complex structural system that supports and protects animal cells, and is often referred to as the connective tissue. The meshlike structure of the ECM is composed of mainly from collagen proteins connected to glycoprotein. As a whole, the structure organizes the exterior of cells and regulates many cell functions such as cell division, motility, embryonic development, and wound healing.
The Extracellular Matrix has many different functions. The ECM forms the mass of skin, bones, and tendons. Its consistency varies from a liquid (blood) to semisolid (cartilage) to solid (bone). Cell activity in and around the matrix yields many different properties from transporting substances to acting as a protective layer. The ECM also forms extracellular structures such as the cornea of the eye and filtering networks in the kidney. It plays a key role in regulating a cell’s behavior including cell division, adhesion, motility, embryonic development, and reactions to wounds and disease. The overall communication of the ECM relies on its fibronectins that bind to receptor proteins (integrins) on the plasma membrane which are also bound to the cytoskeleton (on the cytoplasmic side of the plasmic membrane). The connection from one side of the membrane to the other accomplishes sharing information and communicating changes in the ECM to the cytoskeleton.
The Extracellular Matrix is composed of many different parts such as the cell's plasma membrane, cytoplasm, microfilaments, and receptor proteins (integrin) but is mainly made up of Glycoproteins (made of a core protein with carbohydrate chains). Three main types of glycoproteins (Collagen, Proteoglycans, and Fibronectins) all have different functions that collaborate to regulate various cell functions. Collagen is made of long fibrous glycoproteins whose structures are wound into a triple helix so the resulting fibers have a high tensile strength and great elasticity. They make up tendons, bones, and cartilage, and are the most abundant proteins of the body (in vertebrates). Proteoglycans are glycoproteins that consist of small proteins attached (noncovalently) to long polysaccharides. They regulate movement of molecules through the matrix and also regulate the binding of cations and water. The consistency of the matrix as a whole depends on how much water can be trapped (the more interlinks, the more water can be trapped, making the consistency soft such as that of cartilage). Fibronectins aid in the attachment of cells to the extracellular matrix, help hold the cells in position, and are involved in the wound healing process. Integrins are receptor proteins located across the plasma membrane that bind to microfilaments of the cytoskeleton to communicate changes in the ECM to the cytoskeleton. Components of the ECM are made within the cell and transported to the ECM by exocytosis. The ECM is also made up of Elastin and Laminin. Elastin is the component that allows the ECM to be more 'rubbery' and form elastic structures. Laminin is found in between the cells and it forms webs that help hold them together.