What is the extracellular matrix of connective tissue composed of?
Select all that apply.
A. Protein fibers
B. Ground substance
C. Epithelial tissue cells
D. Connective tissue cells
E. Cytoplasm
The Correct Answer and Explanation is :
The correct answer is:
A. Protein fibers
B. Ground substance
Explanation:
The extracellular matrix (ECM) of connective tissue is a complex network of proteins and other molecules that provides structural and biochemical support to surrounding cells. The ECM plays a crucial role in tissue and organ function by providing a scaffold for cells, enabling communication between cells, and influencing cell behavior like adhesion, migration, and differentiation. The ECM is primarily composed of two main components:
- Protein fibers (Option A):
These are structural components of the ECM and contribute to its tensile strength and elasticity. The main protein fibers found in the ECM are:
- Collagen fibers: These are the most abundant and provide strength and resistance to stretching.
- Elastic fibers: These allow tissues to return to their original shape after stretching.
- Reticular fibers: These form networks that support the cells and tissues, especially in organs like the liver, lymph nodes, and spleen.
- Ground substance (Option B):
This is a gel-like substance that fills the space between the cells and fibers in connective tissue. It consists of water, proteoglycans, glycosaminoglycans (GAGs), and glycoproteins. The ground substance serves as a medium through which nutrients, ions, and metabolic waste products can diffuse between blood vessels and cells. It also plays a role in the hydration and lubrication of tissues.
Incorrect options:
- C. Epithelial tissue cells: These cells are not part of the ECM. They form the outer layers of body surfaces and cavities but do not contribute directly to the ECM in connective tissues.
- D. Connective tissue cells: While these cells (like fibroblasts, chondrocytes, and osteocytes) produce the components of the ECM, they are not themselves part of the matrix. Instead, they secrete the substances that form it.
- E. Cytoplasm: This is the material within a cell, not a component of the ECM. It is responsible for supporting cell functions but does not directly contribute to the extracellular matrix.
In summary, the ECM of connective tissue consists mainly of protein fibers and ground substance, which together provide structural support and allow for communication and transport within tissues.