Overview: The Extracellular Matrix
- Extracellular matrix (ECM) is the organized material outside cells, where large biological molecules form a supportive mesh around and beneath cells.
- Macromolecules are large biological molecules, and the extracellular matrix is built from macromolecules that give tissues strength, structure, and communication cues.
- The extracellular matrix has two broad components: ground substance and fibers.
- Ground substance is the gel-like, non-fibrous part of the extracellular matrix that fills space between cells and fibers.
- Ground substance consists mainly of glycosaminoglycans (GAGs), proteoglycans, and glycoproteins, which help the extracellular matrix hold water, bind signals, and connect cells to surrounding material.
- Fibers are the strand-like structural parts of the extracellular matrix, and they help tissues resist stretching, pulling, and deformation.
- Extracellular environment refers to the extracellular matrix plus water, nutrients, ions, and other small molecules located outside cells.
- Nutrients in the extracellular environment can reach cells because the matrix holds water and creates a route for dissolved substances to move.
- Ions are charged atoms or molecules, and their movement or location outside cells can influence cell behavior.
- Metabolic activity means the chemical work a cell performs, and contact with the extracellular matrix can change that work by sending physical or chemical signals to the cell.
- Cell shape can change when extracellular-matrix attachments pull on the cell surface or reorganize the internal cytoskeleton.
- Cell migration is directed cell movement, and extracellular-matrix molecules can provide tracks, anchors, or cues that help cells move to the correct location.
- Cell-cell interactions can be influenced by the extracellular matrix because matrix attachment affects how cells position themselves near one another.
- Cell division can be affected by extracellular-matrix signals because cells often divide differently depending on whether they are properly anchored.
- Differentiation means a cell becomes more specialized, and extracellular-matrix signals can help guide which specialized features a cell develops.
- Compressive forces push tissue inward, and hydrated ground substance helps tissues resist being squeezed.
- Tensile forces pull or stretch tissue, and extracellular fibers help tissues resist tearing or excessive lengthening.
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