ABSTRACT
This chapter covers the structure, composition, and function of articular cartilage, at the cell and extracellular matrix levels. All chondrocytes within articular cartilage share common traits with respect to gene and protein expressions, surface markers, and cell metabolism. The role of microtubules in intracellular transport is elegantly demonstrated in the assembly of the mitotic spindle, a structure that results in intracellular movement and segregation of replicated DNA into two daughter cells during mitosis. The territorial matrix exhibits higher concentration of proteoglycans than surrounding extracellular matrix, as well as having finer collagen structure. The biochemical structure of the matrix, both fluid and solid fractions, is intimately linked to mechanical function of cartilage. Structurally, intermediate filaments are 10 nm in diameter and "intermediate" in size, being smaller than microtubules but wider than actin microfilaments. In eukaryotic cells, cytoskeleton is comprised of three different filament types that can polymerize from soluble protein monomers into three-dimensional network that couples intracellular components to extracellular stimuli.
