Posterior crico-arytenoid muscle
Musculus cricoarytenoideus posterior
The posterior crico-arytenoid is a fan-shaped laryngeal muscle on the back of the cricoid and the only one that opens the glottis.
At a glance
- English
- Posterior crico-arytenoid muscle
- Latin (TA2)
- Musculus cricoarytenoideus posterior
- System
- Muscle
- Region
- Neck
- Side
- Paired, left and right
About the posterior crico-arytenoid muscle
The posterior crico-arytenoid is a small, paired intrinsic muscle of the larynx lying on the back of the cricoid cartilage, just in front of the lower pharynx. Each muscle is fan-shaped, broad below and converging above. It has a special place among the laryngeal muscles, because it alone separates the vocal folds and opens the airway at the glottis.
It arises from the broad posterior surface of the lamina of the cricoid cartilage, on either side of a midline ridge. Its fibres pass upwards and outwards to the back of the arytenoid's muscular process. The muscle often has two bellies: a medial one with more vertical fibres and a lateral one with more horizontal fibres, ending on different surfaces of the muscular process.
When it contracts, it pulls the muscular process backwards and inwards. This spins the arytenoid outwards, swinging its vocal process and the attached vocal fold away from the midline, and it also slides the arytenoids apart. The rima glottidis is widened, which allows breathing, especially deep or quick breaths. It works against the lateral crico-arytenoid and the arytenoid muscles, which close the glottis, and the balance between them shapes the opening during speech.
Its nerve is the recurrent laryngeal, from the vagus, usually entering as two or three twigs that may join within the muscle, and its blood comes mainly from the inferior laryngeal artery. Because no other muscle can open the vocal folds, paralysis of both posterior crico-arytenoids, as after injury to both recurrent laryngeal nerves, leaves the folds near the midline and can block the airway, needing urgent treatment. After loss of its nerve supply the muscle slowly turns fibrous over months.
Attachments, action and supply
- Origin
- Posterior surface of the lamina of the cricoid cartilage.
- Insertion
- Back of the arytenoid's muscular process.
- Action
- Rotates the arytenoids outwards to abduct the vocal folds and open the rima glottidis.
- Nerve supply
- Recurrent laryngeal nerve (from the vagus, CN X).
- Blood supply
- Inferior laryngeal artery, with branches of the superior laryngeal artery.
Anthromica
See the posterior crico-arytenoid muscle where it really sits, with every layer of the body around it.
- Every layer, one body. Peel from muscle to bone, nerve, vessel and organ, and turn it any way.
- English and Latin. Every structure named the way your exam names it.
- Quiz until it sticks. Short drills on the structures you keep missing.
Free to start. No card.
