Trapezius Muscle

Last update: May 26th, 2023

The trapezius is a diamond-shaped muscle that spans a large portion of the back, from the neck to the lumbar region. It belongs to the extrinsic muscles of the back, specifically the superficial layer. Other muscles in this group include the latissimus dorsi, rhomboid major and rhomboid minor, and levator scapulae.

The trapezius is also referred to as one of the hypaxial back muscles. These muscles are innervated by the ventral (anterior) branches of the spinal nerves, as opposed to the epiaxial muscles, which are supplied by their dorsal (posterior) branches.

The trapezius supports shoulder movements and plays a role in stabilizing and moving the scapula. This is why it is often considered a muscle of the upper extremity.

This article will explain the anatomy and functions of the trapezius muscle.

Trapezius muscle	Descending part	Transverse part	Ascending part
Origin	Superior nuchal line; External occipital protuberance	Spinous processes of the vertebra T1-T4	Spinous processes of the thoracic vertebrae T4-T12
Insertion	Lateral third of the clavicle	Acromion of the scapula; Spine of the scapula	Medial part of the spine of the scapula
Innervation	Accessory nerve (CN XI); Anterior rami of the spinal nerves C3 and C4
Functions	Scapulothoracic joint: Elevates the scapula Atlantooccipital joint: Extends the neck (when contracted bilaterally – from both sides) and laterally flexes the neck (when contracted unilaterally – from one side) Atlantoaxial joint: Enables head rotation	Scapulothoracic joint: Retracts the scapula	Scapulothoracic joint: Depresses the scapula

Trapezius Muscle

Posterior view labeled: Trapezius, deltoid, triceps brachii, latissimus dorsi

Posterior view labeled: Levator scapular, supraspinatus, infraspinatus

Posterior view labeled: Teres minor and major

Posterior view labeled: Rhomboideus minor and major

Posterior view labeled: Trapezius muscle

Attachments of Trapezius Muscle: Origin and insertion

The trapezius muscle consists of three parts:

Descending (superior) part: originates from the superior nuchal line and external occipital protuberance and inserts onto the lateral third of the clavicle;
Transverse (middle) part: originates from the spinous processes of the thoracic vertebrae T1-T4 and inserts onto the acromion and spine of the scapula;
Ascending (inferior) part: originates from the spinous processes of the thoracic vertebrae T4-T12 and inserts onto the medial part of the spine of the scapula.

Learn the anatomy of the trapezius muscle faster with this trunk wall muscle reference chart.

Posterior view labeled: Origin and Insertion

Functions

The descending (superior) part of the trapezius affects three joints:

Scapulothoracic joint: elevates the scapula
Atlantooccipital joint: extends the neck (when contracted bilaterally – from both sides) and laterally flexes the neck (when contracted unilaterally – from one side)
Atlantoaxial joint: enables head rotation

Expand your knowledge with Kenhub free article: Trapezius muscle.

Fifth image in animation of a figure with an elevated scapula

Fourth image in animation of a figure with an elevated scapula

Third image in animation of a figure with an elevated scapula

Second image in animation of a figure with an elevated scapula

First image in animation of a figure with an elevated scapula

The transverse (middle) part of the trapezius draws the scapula medially, a movement known as scapular retraction.

Fourth image in animation of a figure with adducted scapula

Third image in animation of a figure with adducted scapula

Second image in animation of a figure with adducted scapula

First image in animation of a figure with adducted scapula

The ascending part of the trapezius pulls the scapula downward, i.e. scapula.

Fourth image in animation of a figure with depressed scapula

Third image in animation of a figure with depressed scapula

Second image in animation of a figure with depressed scapula

Also, the lower fibers help with upward of the scapula.

First image in animation of a figure with upwardly rotated scapula

Fifth image in animation of a figure with upwardly rotated scapula

Fourth image in animation of a figure with upwardly rotated scapula

Third image in animation of a figure with upwardly rotated scapula

Second image in animation of a figure with upwardly rotated scapula

Innervation

Innervation to the trapezius is supplied by the anterior rami of the spinal nerves C3 and C4, as well as the accessory nerve (cranial nerve XI).

An Overview of the Trapezius Muscle

Posterior view labeled: Trapezius, deltoid, teres minor and major, triceps brachii, latissimus dorsi

Posterior view labeled: Levator scapulae, trapezius, deltoid, teres minor and major, latissimus dorsi, triceps brachii

Posterior view labeled: Levator scapulae, supraspinatus, teres major and minor, triceps brachii, latissimus dorsi

Posterior view labeled: Levator scapulae, infraspinatus, teres major, triceps brachii, latissimus dorsi

Posterior view labeled: Levator scapulae, rhomboideus major and minor, teres major, latissimus dorsi, triceps brachii

Posterior view labeled: Levator scapulae, rhomboideus minor and major, teres major, latissimus dorsi

Posterior view labeled: Levator scapulae, rhomboideus minor and major, teres major

Posterior view labeled: Levator scapulae, rhomboideus minor and major, teres minor

Posterior view labeled: Trapezius, rhomboideus minor and major, teres major, latissimus dorsi

Posterior view labeled: Rhomdoideus minor and major

Posterior view labeled: Rhomdoideus minor

Posterior view labeled: Insertion and origin

Test yourself while observing the trapezius muscle anatomy

Muscles That Act On The Posterior Shoulder

References

Open Anatomy. (n.d.). TA2 Viewer. Retrieved April 5, 2023, from https://ta2viewer.openanatomy.org/
Betts, J. G., Young, K. A., Wise, J. A., Johnson, E., Poe, B., & Kruse, D. H. (2022). Anatomy and Physiology (2nd ed.). OpenStax. https://openstax.org/details/books/anatomy-and-physiology-2e
Palastanga, N., & Soames, R. (2012). Anatomy of Human Movement (6th ed.). Edinburgh, Scotland: Churchill Livingstone.
Moore, K. L. (2018). Clinically Oriented Anatomy (8th ed.). Philadelphia, PA: Wolters Kluwer.
Drake, R. L., Vogl, A. W., & Mitchell, A. W. M. (2015). Gray’s Anatomy for Students (3rd ed.). Edinburgh, Scotland: Churchill Livingstone.