In the labelled diagram of laryngeal intrinsic muscles, which labelled muscle is solely responsible for abduction of the vocal cords?

Appeared in: INI-CET EXAM -2026

Explanation

The muscle labeled 'D' in the diagram is the Posterior Cricoarytenoid.
According to anatomical principles, the Posterior Cricoarytenoid is the only intrinsic laryngeal muscle that performs abduction (opening) of the vocal cords.
Its contraction pulls the muscular processes of the arytenoid cartilages medially and posteriorly, which causes the vocal processes and the attached vocal cords to pivot outwards, thus opening the airway (rima glottidis).
This function is essential for respiration, earning it the name 'safety muscle' of the larynx.

Option B: The Transverse Arytenoid muscle, labeled 'B', is an adductor. It pulls the two arytenoid cartilages together, closing the posterior part of the glottis. Its action is the opposite of abduction.
Option C: The Oblique Arytenoid muscle, labeled 'C', is also an adductor. It works with the transverse arytenoid to close the space between the vocal cords and also helps to close the laryngeal inlet.
Option D: This option is incorrect for two reasons. First, the muscle labeled 'A' is the Lateral Cricoarytenoid, not the Aryepiglottic muscle. Second, both the Lateral Cricoarytenoid and the Aryepiglottic muscle are adductors or sphincters, not abductors. The Lateral Cricoarytenoid adducts the vocal cords, and the Aryepiglottic muscle closes the laryngeal inlet.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy and function of the intrinsic muscles of the larynx as background academic context rather than a clinical decision trigger.
The posterior cricoarytenoid is called the 'safety muscle' because its singular function of opening the vocal cords is essential for life.
Bilateral paralysis of the posterior cricoarytenoid muscles is a medical emergency. The vocal cords remain in the adducted (closed) position, leading to acute airway obstruction and stridor, often requiring an emergency tracheostomy.
Damage to the recurrent laryngeal nerve, which supplies this muscle (and all other intrinsic muscles except the cricothyroid), can occur during thyroid or neck surgery, leading to vocal cord paralysis.

How to Approach the Question

First, analyze the question to identify the key action required: 'solely responsible for abduction of the vocal cords'.
Recall the functions of the intrinsic laryngeal muscles. A critical piece of knowledge is that only one muscle performs abduction, while several perform adduction.
Identify the sole abductor muscle by name: the Posterior Cricoarytenoid.
Examine the provided diagram to locate this muscle. The Posterior Cricoarytenoid is clearly marked with the label 'D'.
Scan the options to find the one that correctly matches the label ('D') with the muscle name ('Posterior cricoarytenoid'). Option A is the correct match.
Confirm the answer by mentally reviewing the functions of the other labeled muscles (A, B, C), recognizing them as adductors, thus ruling them out.

Concept Tested & Keywords

Concept Tested: Anatomy and function of the intrinsic muscles of the larynx.
Stem keywords: laryngeal intrinsic muscles, labelled diagram, abduction, vocal cords
Lead-in keywords: solely responsible
Negative lead-in flag: false

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E6 Anatomy Applied Ashalatha 4e pp. 96-98, 94-96

Practise the full INI-CET EXAM -2026

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