Here's why:

* Connective tissue is a type of tissue that provides support, structure, and connection for other tissues throughout the body. It's composed of cells (like fibroblasts, mast cells, and macrophages) and an extracellular matrix.

* The extracellular matrix is the non-cellular component of connective tissue. It's what gives connective tissue its unique properties and it consists of two main parts:

* Fibers: These are made of proteins like collagen, elastin, and reticular fibers, providing strength, flexibility, and support.

* Ground substance: This is a gel-like substance that fills the space between cells and fibers. It's composed of water, proteoglycans (proteins attached to sugar molecules), and glycoproteins (proteins with attached sugars).

The ground substance plays several key roles:

* Provides a medium for diffusion: Nutrients and oxygen can easily move through the ground substance to reach cells, and waste products can be removed.

* Provides support: It cushions and protects cells and helps maintain the shape of the connective tissue.

* Regulates cell behavior: It can influence cell migration, growth, and differentiation.

Other types of tissues, like epithelial tissue, muscle tissue, and nervous tissue, do not have a significant extracellular ground substance.