Anterior fontanelle closes by what age?
**Core Concept**
The anterior fontanelle is the largest fontanelle in the skull, located at the junction of the two parietal bones and the frontal bone. It is a normal anatomical feature in infants, allowing for flexibility and growth of the skull. The closure of the anterior fontanelle is an important milestone in fetal and infant development.
**Why the Correct Answer is Right**
The anterior fontanelle typically closes by 12-18 months of age. This process is influenced by the rapid growth and ossification of the surrounding bones. The closure of the anterior fontanelle is a sign of normal bone development and is an important indicator of the infant's overall health. As the fontanelle closes, the bones of the skull begin to fuse together, providing a solid foundation for the growing brain.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the posterior fontanelle, not the anterior fontanelle, typically closes by 2-3 months of age.
* **Option B:** This option is incorrect because the closure of the anterior fontanelle does not occur before 6 months of age.
* **Option C:** This option is incorrect because the closure of the anterior fontanelle does not occur after 24 months of age.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the closure of the anterior fontanelle is a normal process, but delayed closure can be a sign of underlying conditions such as rickets or hypothyroidism.
**Correct Answer: D. 12-18 months.**