Epiphyseal plates, commonly known as growth plates, are specialized areas of cartilage found in the bones of children and adolescents. These structures are located near the ends of long bones, such as those in the arms and legs. Their primary function involves facilitating the lengthening of bones, allowing individuals to grow taller. Growth plates are temporary structures crucial for skeletal development, eventually transforming into solid bone.
Structure and How They Work
Epiphyseal plates are composed of hyaline cartilage. Within these plates are specialized cells called chondrocytes, which are responsible for generating new cartilage.
The growth plate is organized into distinct zones, each contributing to the bone lengthening process. Chondrocytes in the zone of proliferation rapidly divide, producing new cells that stack into columns.
As these new cells are formed, older chondrocytes are pushed towards the shaft of the bone, entering the zone of hypertrophy where they enlarge significantly. Following this, the cartilage matrix surrounding these enlarged cells begins to calcify in the zone of calcification.
Subsequently, in the zone of ossification, blood vessels and bone-forming cells called osteoblasts invade the calcified cartilage. Osteoblasts then replace the calcified cartilage with new bone tissue, a process known as endochondral ossification.
This continuous cycle of cartilage production and subsequent replacement by bone allows the long bones to extend in length.
When Growth Plates Close
The process of bone lengthening through epiphyseal plates continues throughout childhood and adolescence. This longitudinal growth eventually ceases when the growth plates close, as the cartilage within them is completely replaced by bone. This transformation typically occurs near the end of puberty, completing height gain.
Hormones play a significant role in signaling the closure of growth plates. For example, increasing levels of sex hormones, such as estrogen, contribute to this process.
Once the cartilage is fully converted to bone, the growth plate becomes an epiphyseal line, which is a subtle bony seam visible on X-rays. For girls, growth plates generally close between 13 and 15 years of age, while for boys, closure typically occurs between 15 and 17 years.
Common Injuries and Their Effects
Epiphyseal plates are inherently weaker than the solid bone surrounding them, making them susceptible to injury. These injuries are particularly common in children and adolescents, accounting for a notable percentage of all childhood fractures.
Common causes include falls, sports-related incidents, and other forms of trauma. Overuse from repetitive activities, such as those in competitive sports, can also contribute to growth plate injuries.
Injuries to a growth plate are a concern because they can disrupt the normal bone lengthening process. If not treated appropriately, these injuries can lead to complications affecting future bone development.
Potential consequences include a limb that ends up shorter or longer than the corresponding limb, or a bone that grows at an abnormal angle. Prompt medical evaluation and treatment are important for suspected growth plate injuries to minimize long-term problems and ensure proper bone healing.