part of bone BTO:0000140 BrendaTissueOBO The hard form of connective tissue that constitutes the majority of the skeleton of most vertebrates; it consists of an organic component (the cells and matrix) and an inorganic, or mineral, component; the matrix contains a framework of collagenous fibers and is impregnated with the mineral component, chiefly calcium phosphate (85 per cent) and calcium carbonate (10 per cent), which imparts the quality of rigidity to bone. osseous tissue connective tissue skeletal system