Extracellular Space

The extracellular space refers to the area outside of cells, filled with extracellular fluid (ECF) and various molecules. It is a key component of all tissues and plays critical roles in communication, transport, and structural support.

• Contents:
  • Water and electrolytes (e.g., Na⁺, Cl⁻, Ca²⁺)
  • Proteins (e.g., albumin, cytokines, enzymes)
  • Lipids and metabolites
  • Extracellular matrix (ECM) components:
    • Collagen, fibronectin, laminin
  • Extracellular vesicles (e.g., exosomes, microvesicles)

• Functions:
  • Facilitates cell-to-cell communication
  • Enables transport of nutrients, oxygen, and waste
  • Provides mechanical and biochemical support
  • Maintains tissue homeostasis
  • Participates in signal transduction (e.g., hormones, neurotransmitters)

• Brain: tightly regulated extracellular space crucial for synaptic transmission
• Connective tissue: ECM-rich, provides mechanical support and elasticity
• Tumor microenvironment: altered extracellular space affects invasion, angiogenesis, and therapy resistance

Note: The composition and regulation of the extracellular space are central to many physiological and pathological processes, including inflammation, cancer, neurodegeneration, and tissue repair.