Which stage occurs at 9-11 weeks in TMJ development?

• A. Blastemic
• B. Cavitation
• C. Maturation
• D. Ossification

Answer: (B)

The key idea is when the TMJ forms its joint space. After the initial mesenchymal condensation (the early blastemal stage), the next essential step is creating a cavity that will become the joint space between the developing condyle and the temporal bone, along with the formation of surrounding structures like the articular disk and capsule. This process, known as cavitation, establishes the synovial cavity and the articulating surfaces that will permit movement. In TMJ development, this cavitation phase occurs around 9 to 11 weeks, which is why that stage is the correct one for the given timeframe. Once the joint space is established, tissues begin more specialized maturation, with cartilage and connective tissues differentiating to form the components of the TMJ, and later ossification proceeding in the relevant regions.