Explain the sequence of intramembranous bone formation.
1. mesenchymal cells condense into a connective tissue membrane
2. mesenchymal cells differentiate into osteoblasts, osteoid is secreted and forms bone spicules
3. calcium phosphate salts are incorporated into osteoid matrix, osteoblasts are surrounded and become osteocytes
4. spicules continue to develop, the spaces inbetween form the marrow cavity, the outer and inner membranes undergo compaction