The movable bone in the skull is?

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2021

Explanation

The mandible, commonly known as the lower jaw, is the only freely movable bone in the adult skull.
It articulates with the left and right temporal bones at the temporomandibular joints (TMJ).
This unique articulation allows for the complex movements necessary for mastication (chewing) and phonation (speech).
All other bones of the skull are fused together by immovable joints called sutures.

Option B: The maxilla forms the upper jaw. It is a paired bone that is fused to the base of the cranium and is therefore immovable.
Option C: The vomer is a single, thin bone that forms the postero-inferior part of the nasal septum. It is fixed and does not move.
Option D: The vault of the head, or calvaria, is the roof of the cranium. It is composed of several flat bones (like the frontal, parietal, and occipital bones) that are joined by immovable fibrous joints called sutures.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy of the skull, specifically identifying the only movable bone as background academic context rather than a clinical decision trigger.
Knowledge of the mandible's mobility is fundamental for assessing facial trauma, temporomandibular joint (TMJ) disorders, and conditions like trismus (lockjaw).
Nurses must provide critical care for patients with mandibular fractures treated with intermaxillary fixation (jaw wiring), prioritizing airway maintenance. Wire cutters must be kept at the bedside for emergency release in case of vomiting or respiratory compromise.
What if? If a patient reports their jaw is 'stuck open' after a wide yawn, the nurse should suspect an anterior dislocation of the mandible at the TMJ. This is a medical emergency requiring immediate manual reduction by a trained provider.

How to Approach the Question

This is a factual recall question testing basic anatomical knowledge.
Identify the keywords in the question: 'movable bone' and 'skull'.
Mentally visualize the skull and its components, or use the provided image as a reference.
Consider the primary functions associated with the skull, such as eating and talking. These actions involve movement of the lower jaw.
Evaluate each option: The maxilla (upper jaw) is fixed. The vomer is an internal bone of the nose and is fixed. The vault (top of the skull) is a solid, fused structure.
Conclude that the mandible is the only option that allows for movement, making it the correct answer.

Concept Tested & Keywords

Concept Tested: Anatomy of the skull, specifically identifying the only movable bone.
Stem keywords: movable bone, skull
Lead-in keywords: is

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E6 Physiology Ganong 27e Vol 2 Part 3 p. 42-44

E6 Anatomy Applied Ashalatha 4e p. 281-283

Practise the full RUHS, Jaipur, PB B.Sc Nursing Entrance-2021

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