Transverse part of trapezius muscle
Pars transversa musculi trapezii
The transverse part of trapezius is the middle portion of the muscle, running horizontally from the upper thoracic spines to the acromion and scapular spine.
At a glance
- English
- Transverse part of trapezius muscle
- Latin (TA2)
- Pars transversa musculi trapezii
- System
- Muscle
- Region
- Back
- Side
- Paired, left and right
About the transverse part of trapezius muscle
Trapezius is the broad, flat muscle covering the nape and upper back on each side, and its fibres are divided by direction into three parts. The transverse part, or middle fibres, lies between the descending part above and the ascending part below. Its fibres run almost horizontally outward from the midline to the shoulder.
They arise from the spine of C7 and the spines of T1 to T3, with the supraspinous ligament between them. In this region the origin is a broad, half-oval aponeurosis that reaches from C6 to T3 and, with the matching part of the other side, forms a tendinous diamond that is visible in muscular backs. The fibres insert on the inner margin of the acromion and on the upper lip of the scapular spine's back edge.
The transverse part draws the scapula towards the vertebral column, bracing the shoulders back. The rhomboids help in this movement, and the upper and lower fibres assist when they act together. It also keeps the scapula steady against the chest wall so that other muscles can move the arm, which matters in pushing, throwing and holding loads away from the body.
It is supplied, like the rest of trapezius, by the accessory nerve, with sensory fibres from C3 and C4. Its blood comes from the transverse cervical artery and the dorsal scapular artery. In facioscapulohumeral muscular dystrophy the middle and lower fibres tend to weaken first, and damage to the accessory nerve also leaves this part weak, so the scapula slides outward and wings slightly.
Attachments, action and supply
- Origin
- Spines of C7 and T1 to T3 and the supraspinous ligament between them.
- Insertion
- Inner margin of the acromion and upper lip of the scapular spine.
- Action
- Retracts the scapula and steadies it against the chest wall.
- Nerve supply
- Accessory nerve (CN XI) for movement; C3 and C4 for sensation.
- Blood supply
- Transverse cervical artery, with branches of the dorsal scapular artery.
Anthromica
See the transverse part of trapezius 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.
