The cartilage that completely encircles the larynx with the narrow part anteriorly and the broad part posteri… - AIIMS Raipur - 2017 (shift-2)

AIIMS Raipur - 2017 (shift-2)

Applied Anatomy

Easy

Appeared in: AIIMS Raipur - 2017 (shift-2)

Explanation

The cricoid cartilage is the only cartilage in the larynx or trachea that forms a complete, circumferential ring, providing structural support to keep the airway open.
It is uniquely shaped like a signet ring, with a narrow arch in the front (anteriorly) and a broad, flat lamina in the back (posteriorly), matching the question's description.
This complete ring structure provides a stable, non-collapsible foundation for the larynx and serves as an attachment point for key muscles, ligaments, and other cartilages.

Option A: The thyroid cartilage is the largest laryngeal cartilage, but it is shield-shaped and incomplete, as it is open at the back (posteriorly). It does not fully encircle the larynx.
Option C: The arytenoid cartilages are small, paired, pyramid-shaped cartilages that sit on top of the cricoid lamina. They are crucial for vocal cord movement but do not form the main structural ring of the larynx.
Option D: The epiglottis is a single, leaf-shaped flap of elastic cartilage. Its function is to cover the opening of the larynx during swallowing to prevent food from entering the airway, not to provide structural encirclement.

Visual 1: Diagram: Anterior, posterior, and lateral views of the laryngeal cartilages, clearly showing the complete ring of the cricoid versus the open, shield-like shape of the thyroid cartilage.
Visual 2: Illustration: A 'signet ring' analogy, visually comparing the shape of the cricoid cartilage to a ring with a large stone to reinforce the concept of a narrow anterior arch and broad posterior lamina.
Visual 3: Animation: A 3D rotation of the larynx, demonstrating how the different cartilages articulate with each other.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy of Laryngeal Cartilages as background academic context rather than a clinical decision trigger.
The cricoid cartilage is a critical landmark for emergency airway procedures. The cricothyroid membrane, located between the thyroid and cricoid cartilages, is the site for a cricothyrotomy.
Applying firm backward pressure on the cricoid cartilage (Sellick's maneuver) can compress the esophagus against the cervical vertebrae, potentially preventing gastric regurgitation and aspiration during emergency intubation.
What if? If a patient has significant facial trauma making oral intubation impossible, a surgeon might perform a cricothyrotomy. A nurse assisting must be able to quickly identify the cricoid cartilage and the cricothyroid membrane to hand the correct equipment and assist effectively.

How to Approach the Question

First, break down the question to identify the key descriptive phrases: 'completely encircles', 'narrow part anteriorly', and 'broad part posteriorly'.
Access your knowledge of laryngeal anatomy. The most important clue is 'completely encircles'. Only one cartilage in the entire airway does this.
Evaluate each option based on this primary clue. The thyroid cartilage is C-shaped (incomplete). The arytenoids are small and paired. The epiglottis is a flap.
This process of elimination leaves only the cricoid cartilage.
Confirm your choice with the secondary clues: 'narrow part anteriorly' (the arch) and 'broad part posteriorly' (the lamina). This 'signet ring' description is a classic mnemonic for the cricoid cartilage.

Concept Tested & Keywords

Concept Tested: Anatomy of Laryngeal Cartilages
Stem keywords: cartilage, larynx, encircles, narrow part anteriorly, broad part posteriorly
Lead-in keywords: is called

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