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Cricothyroid muscle: want to learn more about it?

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Cricothyroid muscle

Cricothyroid muscle (musculus cricothyroideus)

The cricothyroid muscle is a small, bilaterally paired muscle found deep in the anterior compartment of the neck. It is one of the intrinsic laryngeal muscles, accompanied by six other muscles, namely:

The main function of the cricothyroid muscle is to facilitate vocalization. This article will discuss the anatomy and function of the cricothyroid muscle.

Key facts about the cricothyroid muscle
Origin Anterolateral part of cricoid cartilage
Insertion Oblique part: inferior horn of thyroid cartilage
Straight part: inferior margin of thyroid cartilage
Action Draws thyroid cartilage anteroinferiorly. 
Lengthens and tenses vocal ligament (for high pitch sound).
Innervation External laryngeal nerve {of superior laryngeal nerve (CN X)}
Blood supply Cricothyroid artery and vein

Origin and insertion

This short muscle resides deep in the anterior neck, between the cricoid and thyroid cartilages of the larynx. It originates from the anterolateral part of the arch of the cricoid cartilage. The muscle fibers then separate to travel in two groups – oblique and straight. The inferiorly located oblique part travels posterolaterally to insert onto the inferior horn (cornu) of the thyroid cartilage. The straight part travels posterosuperiorly, taking a sharper incline than the fibers of the oblique part, to insert onto the inferior margin of the lamina of the thyroid cartilage

Recommended video: Larynx
Cartilages, ligaments, membranes and muscles of the larynx.

Relations

Each cricothyroid muscle has several important neighbors that serve as important landmarks for surgical planning. Firstly, it is separated from its contralateral fellow by a triangular space occupied by the cricothyroid ligament. This is an important area when establishing an emergency airway (discussed below). The muscle is caudal to the inferior border of the thyroid cartilage and medial to the cricothyroid joint. It travels superior to the lateral cricoarytenoid muscles but deep to the inferior constrictor muscle and its associated tendinous arch. The infrahyoid muscles are also located superficial to the cricothyroid muscle. 

The cricothyroid artery and the external branch of the superior laryngeal nerve approach the muscle from a superolateral angle as it travels toward the midline. The superior poles of the ipsilateral lobe and the pyramidal lobe (when present) of the thyroid gland also partially cover the cricothyroid muscles. 

We don’t want you to get rusty! Take some time and review key structures of the neck.

Innervation

The vagus nerve (CN X) provides motor innervation to the cricothyroid muscle by way of the external branch of the laryngeal nerve. It is the only member of the intrinsic muscles of the larynx that is not supplied by the recurrent laryngeal nerve.

Blood supply

Arterial supply to the cricothyroid muscle is from the cricothyroid artery. This artery arises from the superior thyroid artery, which is a branch of the external carotid artery. The cricothyroid artery crosses superiorly on the anterior cricothyroid ligament to meet with its contralateral counterpart.

A similarly named vein drains the cricothyroid muscle. It is a tributary of the superior thyroid vein, which drains to the internal jugular vein.

Functions

Cartilages and muscles of the larynx

When the cricothyroid muscle contracts, it pulls the thyroid cartilage downward and anteriorly, causing rotation about the cricothyroid joint. This narrows the space between the thyroid and cricoid cartilages, and moves the thyroid cartilage away from the arytenoid cartilage. Consequently, there is stretching (lengthening), tightening and thinning of the vocal folds. Tighter, longer vocal folds produce higher-pitched sounds during vocalization.

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Clinical notes 

The cricothyroid muscle can be injured during a cricothyroidotomy. This is an emergency surgical procedure used to establish a patent airway when other methods are contraindicated. A surgical incision is made anteriorly through the cricothyroid ligament, between the base of the thyroid cartilage and the superior margin of the cricoid cartilage. This airway is meant to be a temporary measure until a definitive airway can be established. 

Cricothyroid muscle: want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 1,230,998 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • Moore, K., Agur, A., & Dalley, A. (2006). Clinically oriented anatomy (5th ed.). Philadelphia: LippincottWilliams&Wilkins.
  • Netter, F. (2014). Atlas of Human Anatomy (6th ed.). Philadelphia, PA: Saunders.
  • Palastanga, N., & Soames, R. (2012). Anatomy and human movement (6th ed.). Edinburgh: Churchill Livingstone.
  • Standring, S., & Gray, H. (2008). Gray's anatomy (42nd ed.). Edinburgh: Churchill Livingstone/Elsevier.

Article, review and layout:

  • Lorenzo Crumbie
  • Nicola McLaren

  • Adrian Rad

Illustrators:

  • Cricothyroid muscle (musculus cricothyroideus) - Yousun Koh
  • Cartilages and muscles of the larynx - Yousun Koh
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