Extracellular Matrix: Function, Components & Definition

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  • 0:00 The Extracellular Matrix
  • 1:00 Production and Components
  • 2:25 Fibrous Proteins
  • 4:25 Proteoglycans
  • 6:15 Lesson Summary
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Lesson Transcript
Instructor: Stephen Christensen
This lesson describes the structure and function of the extracellular matrix, which fills the space between the cells of your tissues. A quiz at the end of the lesson will evaluate what you've learned.

The Extracellular Matrix

Living tissues are not just accumulations of tightly packed cells. Much of a tissue's volume is made up of extracellular space ('extra-' meaning 'outside' or 'beyond,' as in 'extraterrestrial'). This void is filled with a complex meshwork called the extracellular matrix.

Rather than being inert filler material, like the Styrofoam packing around a shipment of glassware, the extracellular matrix is a dynamic, physiologically active component of all living tissues. In addition to providing structural support for the cells embedded within a tissue, the extracellular matrix guides their division, growth, and development. In other words, the extracellular matrix largely determines how a tissue looks and functions.

The extracellular matrix is made up of proteoglycans, water, minerals, and fibrous proteins. A proteoglycan is composed of a protein core surrounded by long chains of starch-like molecules called glycosaminoglycans.

Production and Components

The components of the extracellular matrix are produced and organized by the cells that live within it. In most tissues, fibroblasts, or fiber-making cells, are charged with this responsibility.

In no tissue is the extracellular matrix so well defined - or so easily studied - as in connective tissue, where the extracellular matrix is frequently more plentiful than the cells. Found throughout your body, connective tissue serves as the scaffolding for all other tissues. Variations in the types and numbers of molecules in the extracellular matrix of connective tissue account for the incredible diversity of tissues and organs in the human body.

One vivid example of how the extracellular matrix influences tissue function can be seen in the differences between bone and the cornea of your eye. In bone, the extracellular matrix is thick and highly mineralized, providing a tissue that is hard, inflexible and opaque - just the thing for building a skeleton. In contrast, the cornea's extracellular matrix consists of a water-rich, transparent, flexible gel - ideal for transmitting light into your eyeball.

Two main classes of molecules can be found in the extracellular matrix: fibrous proteins and proteoglycans.

Fibrous Proteins

Several types of fibrous proteins, including collagen, elastin, fibronectin, and laminin, are found in varying amounts within the extracellular matrix of different tissues. These proteins are produced by fibroblasts, but they aren't secreted in their finished form. Rather, they're released as 'precursor' molecules; their subsequent incorporation into the extracellular matrix is guided by the fibroblasts in accordance with the functional needs of a particular tissue.

Collagen is a strong, stretch-resistant fiber that provides tensile strength to your tissues. It's the most abundant protein in the human body. Collagen is the principle constituent of your tendons and ligaments and provides support for your skin. When you sustain an injury to your skin, collagen is the stuff that heals the wound and forms the scar. There are at least a dozen different types of collagen in your body, all adapted to the specific needs of the tissues where they're found.

Elastin is a stretchy and resilient protein. Much like a rubber band, elastin permits tissues to return to their original shape after they've been stretched. Ultraviolet light damages elastin fibers and interferes with their reconstruction, which accounts for the sagging and wrinkling seen in skin that has been chronically exposed to sunlight.

Fibronectin is secreted from fibroblasts in a water-soluble form but is quickly assembled into an insoluble meshwork, which serves several functions. Other cells use the fibronectin matrix to migrate through a tissue, which is particularly important during embryonic development; fibronectin helps position cells within the extracellular matrix; and fibronectin is necessary for cellular division and specialization in many tissues.

Laminin forms sheet-like networks that serve as the 'glue' between dissimilar tissues. It is the principle protein in basement membranes, which are present wherever connective tissue contacts muscle, nervous, or epithelial tissue.


In contrast to fibrous proteins, which provide resistance to stretching forces, proteoglycans provide resistance to compressive, or 'squashing,' forces. This property stems primarily from the glycosaminoglycan portion of proteoglycans.

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