Cricothyroid (Straight Part)

Larynx · Head & Neck

The Cricothyroid (Straight Part) is found among the Larynx muscles of the Head & Neck. Originating at Anterolateral arch of the cricoid cartilage, it inserts at Lower margin of the thyroid lamina. Its chief action is that it tenses and elongates the vocal folds, raising vocal pitch. Its nerve supply is the External laryngeal branch of the superior laryngeal nerve (vagus, CN X).

Origin, Insertion, Action & Nerve

Origin

Anterolateral arch of the cricoid cartilage

Insertion

Lower margin of the thyroid lamina

Action

Tenses and elongates the vocal folds, raising vocal pitch

Nerve

External laryngeal branch of the superior laryngeal nerve (vagus, CN X)

Attachments explained

The Cricothyroid (Straight Part) is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.

Origin

Anterolateral arch of the cricoid cartilage

Insertion

Lower margin of the thyroid lamina

Action & function

When the Cricothyroid (Straight Part) contracts, it produces the following movement: Tenses and elongates the vocal folds, raising vocal pitch.

As part of the Larynx group of the Head & Neck, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.

Nerve supply & clinical relevance

The Cricothyroid (Straight Part) receives its nerve supply from the External laryngeal branch of the superior laryngeal nerve (vagus, CN X).

Because a muscle can only contract when its nerve is intact, injury to the External laryngeal branch of the superior laryngeal nerve can weaken or paralyse the Cricothyroid (Straight Part), impairing the movements it normally produces (tenses and elongates the vocal folds, raising vocal pitch). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Cricothyroid (Straight Part) (the OIANS method)

OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Cricothyroid (Straight Part), work through them in order: picture its origin, trace the muscle to its insertion, reason out the action that shortening between those two points must create, then add the nerve that drives it.

Most students remember the Cricothyroid (Straight Part) fastest by linking its action back to its attachments rather than memorising each fact in isolation. Once the origin and insertion make sense, the action usually follows logically.