Cartilage perichondrium, light micrograph. The perichondrium corresponds to the connective tissue sheath of the cartilage. This is an oblique section of the boundary between the perichondrium and the cartilage. The collagen fibres can be seen penetrating from the perichondrium (right) and entering and intermingling with the cartilaginous matrix in the most peripheral part of the cartilage, determining a very firm union of the perichondrium. At left are the rounded chondrocytes organized in small cell groups called isogenic groups. Deeper into the cartilage tissue, the matrix that surrounds the chondrocytes is more bluish, as it is richer in amorphous substance.