the growth and development of the skeleton begins early in the life of an embryo and continues until the late teens. the embryonic skeleton is initially made up of flexible connective tissues,either fibrous membranes or pieces of hyaline cartilage. by the time it has reached 8 weeks old,the process of ossification has started to replace these structures with hard born tissue,and over the ensuing months and years bones grow and develop. two different methods of ossification replace original connective tissue with bony matrix. lntramembranous ossification forms the bones of the skull from fibrous membranes.endochondral ossification replaces hyaline cartilage to from the majority of bones,other than those in the skull.the sequence shows the progress of endochondral ossification in along bone from the cartilage template of a young embryo to the hard,weight-bearing bone of a 6-year-old child that will increase yet more in length and width to enable the child to grow.