Human Body Stages Of Growth

The human body starts to grow from the moment we are conceived and continues throughout the period of fetal development. We grow most rapidly before we are born.

Fetal Development

8 Weeks - Arms, legs and major joints are forming. Toes and fingers are distinct but may still be joined by webbing.

12 Weeks - Major internal organs are formed and nails are beginning to grow. External ears, eyelids and permanent teeth buds have usually formed.

16 Weeks - External genital organs are visible and hair begins to appear all over the body.

40 weeks - The fetus is now mature and ready to be born.

Changes in Body Proportion

  • In a newborn infant the head represents about one quarter of the baby's total length.
  • As the child grows the relative sizes of the head and trunk decrease and the limbs lengthen.
  • At final adult height the head is only about one eighth of our total height.

Hard Bone Development

  • During childhood the development of hard bone and the growth of bones is a continuous process.
  • Hard bone development starts before birth at zones in the bone shafts called primary ossification centres.
  • In a newborn baby only the bone shafts are hard bone - the bone ends are made of cartilage.
  • As the child develops, secondary hard bone centres form in the bone ends.
  • By the age of 18 the cartilage has been replaced by bone and growth is complete.

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