The Extrinsic Muscles of the Shoulder - Podcast Version 0:00 / 0:00 1x 0.25x 0.5x 0.75x 1x 1.25x 1.5x 1.75x 2x The muscles of the shoulder are associated with movements of the upper limb. They produce the characteristic shape of the shoulder, and can be divided into two groups: Extrinsic – originate from the torso, and attach to the bones of the shoulder (clavicle, scapula or humerus). Intrinsic – originate from the scapula and/or clavicle, and attach to the humerus. Note: there are other muscles that act on the shoulder joint – the muscles of the pectoral region, and the upper arm. In this article, we shall look at the anatomy of the extrinsic muscles of the shoulder – their attachments, innervation, and actions. The extrinsic muscles of the shoulder originate from the trunk, and attach to the bones of the shoulder – the clavicle, scapula, or humerus. They are located in the back, and are also known as the superficial back muscles. The muscles are organised into two layers – a superficial layer and a deep layer. Pro Feature - 3D Model You've Discovered a Pro Feature Access our 3D Model Library Explore, cut, dissect, annotate and manipulate our 3D models to visualise anatomy in a dynamic, interactive way. Learn More Superficial There are two superficial extrinsic muscles – the trapezius and latissimus dorsi. Trapezius The trapezius is a broad, flat, and triangular muscle. The muscles on each side form a trapezoid shape. It is the most superficial of all the back muscles. Attachments: Originates from the skull, nuchal ligament and the spinous processes of C7-T12. The fibres attach to the clavicle, acromion, and the scapula spine. Actions: The upper fibres of the trapezius elevate the scapula and rotates it during abduction of the arm. The middle fibres retract the scapula and the lower fibres pull the scapula inferiorly. Innervation: Motor innervation is from the accessory nerve. It also receives proprioceptor fibres from C3 and C4 spinal nerves. Clinical Relevance Testing the Accessory Nerve The most common cause of accessory nerve damage is iatrogenic (i.e. due to a medical procedure). In particular, operations such as cervical lymph node biopsy or cannulation of the internal jugular vein can cause trauma to the nerve. To test the accessory nerve, trapezius function can be assessed. This can be done by asking the patient to shrug his/her shoulders. Other clinical features of accessory nerve damage include muscle wasting, partial paralysis of the sternocleidomastoid, and an asymmetrical neckline. Latissimus Dorsi The latissimus dorsi originates from the lower part of the back, where it covers a wide area. Attachments: Has a broad origin – arising from the spinous processes of T7-T12, iliac crest, thoracolumbar fascia and the inferior three ribs. The fibres converge into a tendon that attaches to the intertubercular sulcus of the humerus. Actions: Extends, adducts, and medially rotates the upper limb. Innervation: Thoracodorsal nerve. Pro Feature - Dissection Atlas The superficial and intermediate muscles of the back The superficial and intermediate muscles of the back You've Discovered a Pro Feature Access our Dissection Image Library Enhance your understanding with high-resolution dissection images showcasing real-life anatomy. Learn More Deep There are three muscles in this group – the levator scapulae and the two rhomboids. They are situated in the upper back, underneath the trapezius. Levator Scapulae The levator scapulae is a small strap-like muscle. It begins in the neck and descends to attach to the scapula. Attachments: Originates from the transverse processes of the C1-C4 vertebrae and attaches to the medial border of the scapula. Actions: Elevates the scapula. Innervation: Dorsal scapular nerve. Rhomboids There are two rhomboid muscles – major and minor. The rhomboid minor is situated superiorly to the major. Rhomboid Major Attachments: Originates from the spinous processes of T2-T5 vertebrae. Attaches to the medial border of the scapula, between the scapula spine and inferior angle. Actions: Retracts and rotates the scapula. Innervation: Dorsal scapular nerve. Rhomboid Minor Attachments: Originates from the spinous processes of C7-T1 vertebrae. Attaches to the medial border of the scapula, at the level of the spine of scapula. Actions: Retracts and rotates the scapula. Innervation: Dorsal scapular nerve. By TeachMeSeries Ltd (2026) Fig 1The extrinsic muscles of the shoulder. Do you think you’re ready? Take the quiz below Pro Feature - Quiz The Extrinsic Muscles of the Shoulder Question 1 of 3 Submitting... Skip Next Rate question: You scored 0% Skipped: 0/3 1800 More Questions Available Upgrade to TeachMeAnatomy Pro Challenge yourself with over 1800 multiple-choice questions to reinforce learning Learn More Frequent questions What are the extrinsic muscles of the shoulder? The extrinsic muscles of the shoulder are those that originate from the torso and attach to the shoulder bones, including the clavicle, scapula, and humerus. They are primarily responsible for the movement and shape of the shoulder and are classified into superficial and deep layers. What is the function of the trapezius muscle? The trapezius muscle elevates, retracts, and rotates the scapula, playing a crucial role in shoulder movements. Its upper fibres elevate the scapula, while the middle fibres retract it, and the lower fibres pull it inferiorly. How is the latissimus dorsi muscle innervated? The latissimus dorsi muscle is innervated by the thoracodorsal nerve. This nerve is responsible for controlling the muscle's actions, which include extending, adducting, and medially rotating the upper limb. What are the attachments of the levator scapulae muscle? The levator scapulae muscle originates from the transverse processes of the C1-C4 vertebrae and attaches to the medial border of the scapula. This muscle primarily functions to elevate the scapula. What are the clinical implications of accessory nerve damage related to the trapezius? Accessory nerve damage can result from medical procedures, leading to trapezius dysfunction, which can be assessed by asking a patient to shrug their shoulders. Symptoms may include muscle wasting, partial paralysis of the sternocleidomastoid, and an asymmetrical neckline. Rate This Article