Identify the fontanel indicated by the arrow.

AIIMS Jodhpur SNO-2023

Applied Anatomy

Easy

Appeared in: AIIMS Jodhpur SNO-2023

Explanation

The image displays a large, diamond-shaped membranous gap, which is the defining characteristic of the anterior fontanel.
This fontanel is located at the junction of the frontal, parietal, and sagittal sutures, consistent with the anatomical position of the anterior fontanel.
It is the largest of the fontanels and remains open until approximately 12-18 months of age, making it a key landmark in infant assessment.
This structure is also known as the bregma.

Option B: The posterior fontanel is located at the back of the head, is triangular in shape, and is much smaller than the structure shown.
Option C: The temporal (or sphenoidal) fontanels are located on the sides of the skull, at the junction of the sphenoid, temporal, frontal, and parietal bones. They are not visible in this superior view.
Option D: The occipital fontanel is another name for the posterior fontanel. As explained above, it is incorrect because it is triangular, smaller, and located at the back of the head.

Visual 1: Diagram - A labeled diagram of an infant's skull from a superior view, clearly showing the anterior fontanel, posterior fontanel, and the associated sutures (sagittal, coronal, lambdoid, frontal). This helps differentiate the fontanels by shape and location.
Visual 2: Diagram - A lateral view of the infant skull to show the location of the less commonly assessed sphenoidal (anterolateral) and mastoid (posterolateral) fontanels.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy of the infant skull and identification of fontanels as background academic context rather than a clinical decision trigger.
Assessing the fontanels is a fundamental nursing skill in pediatrics. The tension and fullness of the fontanel provide immediate clues about an infant's hydration status and neurological condition.
A sunken fontanel in an infant with a history of diarrhea and vomiting is a classic sign of dehydration, prompting the nurse to initiate rehydration protocols and monitor intake/output.
A bulging, tense fontanel is a red flag for increased intracranial pressure (ICP), which could be due to meningitis, hydrocephalus, or head trauma. This requires immediate medical evaluation.

How to Approach the Question

First, identify the anatomical view presented in the image. This is a superior (top-down) view of a skull.
Next, carefully observe the structure indicated by the arrow. Note its key features: shape (diamond), size (large), and location relative to the surrounding bones and suture lines.
Recall the characteristics of the different fontanels. The anterior fontanel is diamond-shaped and the largest, while the posterior is triangular and smaller.
Compare your observations from the image with the characteristics of the options provided.
The diamond shape seen in the image directly matches the description of the anterior fontanel.
Eliminate the other options based on their incorrect shape (triangular for posterior/occipital) or location (lateral for temporal).

Concept Tested & Keywords

Concept Tested: Anatomy of the infant skull and identification of fontanels.
Stem keywords: fontanel, arrow, infant skull
Lead-in keywords: Identify
Clinical cues: The image shows a superior view of an infant skull, which is the standard perspective for assessing the major fontanels.

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