Anterior fontanelle ossifies by: March 2007
**Core Concept**
The anterior fontanelle is a fibrous gap in the skull that remains patent after birth, allowing for brain growth and development. Ossification of the anterior fontanelle is a critical process that occurs in early childhood.
**Why the Correct Answer is Right**
The anterior fontanelle ossifies due to the closure of the metopic suture, which is a fibrous joint that separates the two halves of the frontal bone. This process occurs around 18-24 months of age, as the frontal bone grows and the metopic suture gradually closes. The metopic suture closure is a result of the deposition of new bone tissue by osteoblasts, which helps to strengthen the skull and reduce the risk of injury.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the posterior fontanelle, not the anterior fontanelle, typically closes first, around 2-3 months of age.
**Option B:** This option is incorrect because the coronal sutures, which separate the frontal and parietal bones, do not directly contribute to the ossification of the anterior fontanelle.
**Option C:** This option is incorrect because the sagittal suture, which separates the two parietal bones, does not play a role in the ossification of the anterior fontanelle.
**Clinical Pearl / High-Yield Fact**
It's essential for pediatricians and neonatologists to monitor the anterior fontanelle for signs of premature closure, which can be associated with craniosynostosis, a condition where the sutures of the skull fuse prematurely.
**Correct Answer:** C.