Grades 9–12 · Organisms
How can a solid bone grow longer?
A growing long bone does not lengthen by stretching all of its existing hard tissue. Near each end is a growth plate, a region of cartilage between the end of the bone and its shaft. Different zones in this plate carry out connected stages of growth.
In the diagramA growth plate lets a long bone lengthenAn enlarged strip between the bone end and shaftBone endCartilage cellsdivideCells enlargeBone is depositedtoward the shaftGrowth stops when the plate closes into boneThis shows zones, not a personal growth forecast.
Cartilage cells called chondrocytes multiply in columns. Farther toward the shaft, cells enlarge and the surrounding matrix changes and calcifies. Blood vessels and bone-forming cells enter the region. Osteoblasts deposit bone on remaining scaffolds of calcified cartilage as the tissue is remodeled.
Production and enlargement of cartilage move the bone end farther from the shaft, while replacement adds bone toward the shaft. These are neighboring zones operating together, rather than the entire plate passing through a single stage at once. The diagram separates the zones to make that spatial sequence visible.
Hormones and local signals regulate these processes. Eventually cartilage growth ends and the plate is replaced by bone, leaving an epiphyseal line. Lengthening at that plate stops, although bone remains living and can continue remodeling. No single growth-plate picture can predict a person’s final height.
About this explanation
Starting knowledge: Understand cells divide, cartilage differs from bone and osteoblasts deposit bone matrix.
Sources
- OpenStax, Anatomy and Physiology 2e — Bone Formation and Development