Extracellular matrix made up of mesenchymal cells and forms the stroma of organs is called the...

• A. Hyaluronic acid
• B. Interstitium
• C. Basement membrane
• D. Collagen

Answer: (B)

The interstitium is the connective tissue framework of an organ, formed by mesenchymal-derived cells that lay down the extracellular matrix to create the supportive stroma surrounding the functional cells. This matrix fills the space between parenchymal cells and provides structure, mechanics, and signals essential for tissue function. Hyaluronic acid is one component of the ECM, but it does not denote the entire matrix. The basement membrane is a distinct, thin barrier between epithelium (or endothelium) and underlying stroma, not the general connective tissue framework. Collagen is a major constituent of the ECM within the interstitium, but the term interstitium best captures the overall connective tissue network that forms the organ’s stroma.