The growth plate (also known as the physis) is a complex structure with many different types of cells (bone, cartilage, collagen) and multiple layers. There is a network of tiny blood vessels called capillaries to supply the area with nutrients and oxygen.
The physis is unique because it must be flexible enough to grow (i.e., it has not yet hardened into bone). But it must also be strong enough to withstand tension, compression, and shear loads placed on it during the many and varied activities of children.
Growth is regulated by hormones, feedback loops, and factors that signal when to increase or decrease cell growth and when to stop growth altogether. Collagen is the basic building block of all soft tissues and bone. In order to turn collagen into bone, there has to be just the right amount of calcium, alkaline phosphatase, and matric metalloproteinase.
There are actually tiny packets called vesicles inside the chondrocytes (cartilage cells) that contain these chemicals. By some mechanism at the cellular level, these vesicles open up and release their contents at just the right moment for mineralization of the bone.
Anything that disrupts even one of these pathways can lead to abnormal physis. Lead poisoning, metabolic bone disease, tumors, infection, and trauma head the list of reasons why bone growth can get stunted or altered.
Disturbance of the growth plate resulting in stopping bone growth can lead to a limb length difference (arm or leg) from one side to the other. Studies show that up to one-third of all bone fractures in children that extend into the physis result in this type of growth disturbance.
The factors that determine growth problems after fracture include the location of the injury, whether or not the blood vessels to the physis were damaged, and how close the child was to skeletal maturity (end of bone growth) at the time of the fracture.
Understanding growth plate biology, anatomy, and physiology is an important tool. Today’s 6th graders who understand the basics of physeal growth and development may become tomorrow’s scientists finding ways to repair and restore damaged growth plates. Kudos to you for trying to gather a bit of knowledge and come alongside her in this project!