Chondrocytes are the essential cells of the cartilage tissue. They are large secretory cells, with a spherical nucleus and a prominent nucleolus. They derive from chondroblasts, which are immature cartilage-producing cells and they are found embedded in the lacunae of the cartilage matrix. Each living chondrocyte occupies a lacuna, which is a compartment in the extracellular matrix. They are found in greater number in hyaline cartilage. Function: they synthesize large amount of protein and polysacharide (sugar) for secretion and store large amount of nutrients since they exist far from blood vessels.
Initially, the chondrocytes are basophilic, which means they get stained with basic dyes. This indicate that they have an extensive rough endoplasmic reticulum (rER). However, they later acquire numerous fat droplets as they appear vacuolated. They have a large, spherical and euchromatic nucleus. Their cytoplasm contains numerous mitochondria and a well-developed Golgi apparatus. The mitochondria supply adenosine triphosphate (ATP) for energy consuming functions, such as protein synthesis and the transport of amino acids and sugar precursors for the extracellular matrix constituents.
The chondrocytes have many cytoplasmic vacuoles that bud from the distal face (maturing face) of the Golgi apparatus. The vacuoles contain fibrous materials (collagen precursors) and amorphous materials (cartilage proteoglycan aggregates and glycoproteins).
Below, an electron micrograph of a chondrocyte. N: nucleus; RER: rough endoplasmic reticulum; G: Golgi apparatus; and IM: intercellular matrix.
