Time period Bones affected Third month of fetal development Ossification in long bones beginning Fourth month Most primary ossification centers have appeared in the diaphyses of bone. Birth to 5 years Secondary ossification centers appear in the epiphyses 5 years to 12 years in females, 5 to 14 years in males Ossification is spreading rapidly from the ossification centers and various bones are becoming ossified 17 to 20 years Bone of upper limbs and scapulae becoming completely ossified 18 to 23 years Bone of the lower limbs and os coxae become completely ossified 23 to 25 years Bone of the sternum, clavicles, and vertebrae become completely ossified By 25 years Nearly all bones are completely ossified
when do the bones of the sternum become completely ossified
23 to 25 years