Final answer:
The extracellular matrix (ECM) is the most abundant extracellular material, made mainly of collagen and proteoglycans. It provides structural support and facilitates communication between cells, particularly abundant in connective tissues. It is not composed of actin but includes glycoproteins and is critical for tissue integrity.
Step-by-step explanation:
The extracellular matrix (ECM) is not composed of strands of actin protein; rather, it is the most abundant extracellular material, especially in connective tissue. Actin forms part of the cytoskeleton's microfilaments, which are involved in various cellular activities such as muscle contraction and cell support. The ECM, however, is comprised primarily of proteins, with the most abundant protein being collagen.
Collagen fibers are intertwined with proteoglycans, which are carbohydrates that contain protein molecules. This combination forms a complex and supportive network outside of the plasma membrane. The ECM is critical for not only maintaining tissue structural integrity but also enabling communication between cells within a tissue, allowing them to withstand physical stresses and transmit signals. It is a meshwork of macromolecules that includes glycoproteins such as collagen and fibronectin, to which cells can directly attach.
The role of the ECM is particularly notable in connective tissue, where it is highly abundant and essential to the tissue's function. Connective tissue cells are embedded in a significant amount of extracellular material, which is secreted by the cells themselves and allows for extensive functionality including the attachment of microbial pathogens like Streptococcus pyogenes.