Straight part of cricothyroid muscle
Pars recta musculi cricothyreoidei
The straight part of cricothyroid is the front, near-vertical portion of the cricothyroid muscle, linking the cricoid arch to the thyroid cartilage.
At a glance
- English
- Straight part of cricothyroid muscle
- Latin (TA2)
- Pars recta musculi cricothyreoidei
- System
- Muscle
- Region
- Neck
- Side
- Paired, left and right
About the straight part of cricothyroid muscle
Cricothyroid is the only intrinsic muscle of the larynx that lies on its outer surface. It fills the angle between the arch of the cricoid cartilage and the lower edge of the thyroid cartilage, and it has two parts. The straight part, pars recta, is the anterior portion, whose fibres run almost straight up. The oblique part lies behind it and runs backward as well as upward.
The straight part arises from the front and side of the outer surface of the cricoid arch. Its fibres rise steeply to the lower border of the thyroid lamina, near the front of the cartilage. In the midline the two cricothyroid muscles are separated by a small triangular gap covered by the median cricothyroid ligament.
When the muscle contracts it tilts the thyroid cartilage forwards and downwards on the cricoid, or brings the cricoid arch up towards the thyroid, at the cricothyroid joints. This increases the distance between the angle of the thyroid cartilage, where the vocal folds attach in front, and the arytenoid cartilages behind. The vocal folds are lengthened and tensed, which raises the pitch of the voice. The straight part gives the main rocking movement, while the oblique part slides the thyroid forwards.
Cricothyroid is supplied by the external branch of the superior laryngeal nerve, unlike the other intrinsic laryngeal muscles, which receive the recurrent laryngeal nerve. The external branch runs close to the superior thyroid artery, so it can be injured when that artery is tied during thyroid surgery. Damage leaves a weak, low voice that tires quickly and cannot reach high notes.
Attachments, action and supply
- Origin
- Front and side of the outer surface of the cricoid arch.
- Insertion
- Lower border of the thyroid lamina, towards its front.
- Action
- Tilts the thyroid cartilage forwards on the cricoid, lengthening and tensing the vocal folds to raise pitch.
- Nerve supply
- External branch of the superior laryngeal nerve (vagus).
- Blood supply
- Cricothyroid branch of the superior thyroid artery.
Anthromica
See the straight part of cricothyroid 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.
