Final answer:
The last bone to ossify in the human body, typically around the age of 25, is the clavicle. Two types of ossification contribute to bone development: intramembranous, mostly involved in flat bones, and endochondral, which is responsible for the lengthening of long bones. Ossification is completed when the epiphyseal plates close in early adulthood.
Step-by-step explanation:
The last bone in the body to ossify typically completes the process in early adulthood, around the age of 25. The process of ossification wherein bones become increasingly ossified and grow larger occurs during fetal development, childhood, and adolescence, reaching skeletal maturity by about age 20. Two distinct methods of ossification occur: intramembranous ossification and endochondral ossification.
Intramembranous ossification is responsible for the formation of flat bones like those of the skull and the clavicle. The clavicle, beginning ossification during the fifth week of development, is not only the first bone in the body to start ossifying but also one of the last to complete ossification.
Endochondral ossification involves the replacement of hyaline cartilage with bone, contributing to the growth in length of the long bones in the appendicular skeleton. The presence of the epiphyseal plate, or growth plate, is essential for this process, and it persists until full maturity is reached when the bone can no longer grow in length.
The ongoing growth of the epiphyseal plate is critical for long bones to continue increasing in length throughout childhood. Once a person reaches full skeletal maturity, the epiphyseal plates close, and the ossification centers fuse, marking the completion of bone development and growth.