The primary difference between primary and secondary cartilage lies in their response to growth stimuli.
Understanding Primary and Secondary Cartilage
To understand the difference, let's first define each type of cartilage:
- Primary Cartilage: This type of cartilage develops directly from the mesenchyme, a type of embryonic connective tissue. It primarily responds to systemic growth stimuli like hormones.
- Secondary Cartilage: This type of cartilage doesn't directly develop from mesenchyme. It's usually found in areas undergoing significant adaptation or growth in response to functional demands. It primarily responds to local growth factors, following the systemic hormonal signals secondarily (Enlow, 1992; Sperber, 2001).
Key Differences Summarized
| Feature | Primary Cartilage | Secondary Cartilage |
|---|---|---|
| Development | Directly from mesenchyme | Not directly from mesenchyme |
| Growth Stimuli Response | Primarily to systemic (hormonal) factors | Primarily to local growth factors, then systemic |
| Location Example | Growth Plates of Long Bones | Mandibular Condyle |
Explanation of Differences
The different growth stimuli response is a crucial distinguishing factor. Primary cartilage, such as the cartilage found in the growth plates of long bones, responds primarily to hormones circulating throughout the body. This ensures coordinated growth of the entire skeleton.
In contrast, secondary cartilage (such as that found in the mandibular condyle of the jaw) is more responsive to local environmental factors. These local factors influence the growth and remodeling of the cartilage in response to functional demands, such as chewing. These local factors might include muscle activity or pressure from adjacent tissues. Systemic factors still play a role, but their influence is secondary, and the local factors have a more direct impact.
For example, in mandibular growth, both hormones and local influences regulate the growth of the mandibular condylar cartilage. Growth in the mandible is not solely based on the hormone concentration but also depends on the functional environment and biomechanical forces acting on the cartilage.
