How does the growth plate allow a child’s bones to lengthen?

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Internal structure of a human long bone — bone A long bone of the human body, showing a magnified cross section of the interior.

The growth plate, also known as the epiphyseal plate, facilitates longitudinal bone growth through a continuous process of endochondral ossification. This mechanism relies on the highly ordered rows of cartilage cells within the plate.1

The process occurs in two synchronized stages:
* Cartilage Production: The germinal layer, located farthest from the bony shaft, is responsible for constant cell replication and the production of new cartilage.1
* Replacement by Bone: On the side of the plate facing the shaft, cartilage cells undergo degeneration and calcification. This calcified cartilage is then replaced by true bone, known as primary spongiosa.1

Because the rate of new cartilage production is closely matched by the rate at which it is replaced by bone, the bone is able to extend in length. This cycle continues throughout childhood and adolescence until skeletal maturity is reached, at which point the growth plates fuse and disappear.1