Question:easy
Which fontanelle is the last to close?
Which fontanelle is the last to close?
Show Hint
The diamond-shaped anterior fontanelle closes at 18 to 24 months.
Updated On: Jun 24, 2026
- Anterolateral
- Anterior
- Lateral
- Occipital
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Order the four fontanelles by their closure timeline rather than by position, since the question is about which shuts last.
Step 2: Going from earliest to latest: posterior (occipital) at 2 to 3 months, sphenoidal (anterolateral) near 6 months, mastoid (posterolateral) from 6 to 18 months, and finally the anterior fontanelle at 18 to 24 months. The one at the end of this sequence is the anterior fontanelle, so option B is correct.
Step 3: Cross off the rest. The anterolateral and lateral (mastoid) fontanelles close well before two years, and the occipital fontanelle is the very first to close, making them incorrect for the last-to-close question.
\[\boxed{\text{Anterior fontanelle}}\]
Step 2: Going from earliest to latest: posterior (occipital) at 2 to 3 months, sphenoidal (anterolateral) near 6 months, mastoid (posterolateral) from 6 to 18 months, and finally the anterior fontanelle at 18 to 24 months. The one at the end of this sequence is the anterior fontanelle, so option B is correct.
Step 3: Cross off the rest. The anterolateral and lateral (mastoid) fontanelles close well before two years, and the occipital fontanelle is the very first to close, making them incorrect for the last-to-close question.
\[\boxed{\text{Anterior fontanelle}}\]
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