Normal shape of anterior fontanelle is

Appeared in: UPPSC 2017

Explanation

The anterior fontanelle, or bregma, is a soft membranous gap on an infant's skull located at the junction of the sagittal, coronal, and frontal sutures.
The intersection of these four suture lines (one frontal, one sagittal, two coronal) gives the anterior fontanelle its characteristic diamond shape.
It is the largest of the fontanelles and typically measures about 2.5 cm x 2.5 cm.
This shape and size allow for the molding of the fetal head during birth and accommodate the rapid growth of the brain during infancy.

Option A: Fontanelles are formed by the meeting of linear bone sutures, which results in angular shapes, not a round one.
Option B: While it has four sides, the anterior and posterior angles are more acute than the side angles, creating an elongated diamond shape rather than a square with four equal sides and 90-degree angles.
Option D: This is the characteristic shape of the posterior fontanelle (lambda), not the anterior fontanelle.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy and assessment of neonatal fontanelles as background academic context rather than a clinical decision trigger.
Assessing the anterior fontanelle is a key nursing skill for evaluating infant hydration and intracranial pressure. A sunken fontanelle suggests dehydration, while a bulging fontanelle can indicate increased intracranial pressure.
The fontanelle should feel soft and flat when the infant is calm and held upright. Pulsations are a normal finding.
What if? If a 2-year-old child presents with an open anterior fontanelle, it is an abnormal finding that requires further investigation for conditions like hypothyroidism, hydrocephalus, or certain genetic syndromes, as it should normally close by 18 months.

How to Approach the Question

This is a factual recall question about neonatal anatomy.
Identify the key term in the question: 'anterior fontanelle'.
Recall or visualize the anatomy of the infant skull. The fontanelles are the 'soft spots'.
Differentiate between the two main fontanelles: anterior and posterior.
Recall the specific shape associated with the anterior fontanelle (diamond) and the posterior fontanelle (triangular).
Compare this recalled fact with the given options and select the correct one.

Concept Tested & Keywords

QvIcYB6QIv_vcAWoxKXHZC

E6 Nelson Textbook of Pediatrics(2024) — Volume 2 p. 1357-1359

E6 Midwifery Obstetrics and Gynecology Nursing Sandeep Kaur p. 53-66

Practise the full UPPSC 2017

Attempt every question from this paper in a timed mock, then review the full solution for each one.