Maximus Gage
The scapula, or shoulder blade, is a flat, triangular bone that sits above the rib cage in the upper back. It connects the clavicle to the humerus, forming the shoulder joint. The scapula can move in six directions, and each movement is produced by specific muscles. The muscles that adduct the scapula include the teres major, latissimus dorsi, and coracobrachialis. The teres major originates from the posterior surface of the scapula and performs adduction and medial rotation at the shoulder joint. The latissimus dorsi originates from the inferior angle of the scapula and performs adduction, extension, and medial rotation. The coracobrachialis originates from the coracoid process and performs adduction and flexion at the shoulder joint.
| Characteristics | Values |
|---|---|
| Muscles that adduct the scapula | Latissimus dorsi, Teres major, Pectoralis minor, Pectoralis major, Serratus anterior, Trapezius, Levator scapulae, Rhomboid major, Coracobrachialis, Triceps, Biceps |
| Function | The scapula, or shoulder blade, is a sturdy, flat, triangular bone that connects the clavicle to the humerus. It forms the posterior of the shoulder girdle. |
| Movement | The scapula moves in six directions: protraction, retraction, elevation, depression, upward rotation, and downward rotation. |
| Muscles responsible for movement | Protraction: Serratus anterior, Pectoralis major, and Pectoralis minor. Retraction: Trapezius, Rhomboids, and Latissimus dorsi. Elevation: Trapezius, Levator scapulae, and Rhomboid major. Depression: Latissimus dorsi, Serratus anterior, Pectoralis major and minor, and Trapezius. Upward rotation: Trapezius and Serratus anterior. Downward rotation: Latissimus dorsi, Levator scapulae, Rhomboids, and Pectoralis major and minor. |
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Latissimus Dorsi
The latissimus dorsi is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline. The word "latissimus dorsi" comes from Latin and means "broadest [muscle] of the back", with "latissimus" meaning "broadest" and "dorsum" meaning "back". Bodybuilders often refer to the pair of muscles as "lats". The latissimus dorsi is the widest muscle in the human body and is relatively thin, covering almost all back muscles at the posterior trunk, except the trapezius.
The latissimus dorsi is responsible for extension, adduction, transverse extension (also known as horizontal abduction or horizontal extension), flexion from an extended position, and (medial) internal rotation of the shoulder joint. It also plays a role in the extension and lateral flexion of the lumbar spine. The muscle's actions on moving the arms can influence the movement of the scapulae, such as their downward rotation.
The latissimus dorsi is supplied by the thoracodorsal artery, a continuation of the subscapular artery, which is a branch of the third part of the axillary artery. It also receives blood supply from the dorsal perforating branches of the inferior three posterior intercostal arteries and the superior three lumbar arteries. The thoracodorsal nerve, a branch of the posterior cord of the brachial plexus, provides innervation to the latissimus dorsi.
The latissimus dorsi works collaboratively with the teres major and pectoralis major to perform actions of the upper extremity, including adduction, medial rotation, and extension of the arm at the glenohumeral joint.
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Teres Major
The teres major is a small muscle that runs along the lateral border of the scapula. It is one of the seven scapulohumeral muscles that act around the glenohumeral joint to facilitate shoulder movement. The teres major is also one of the four rotator cuff muscles, along with the subscapularis, teres minor, and infraspinatus. These muscles attach to the scapular surface and assist with abduction and external and internal rotation of the glenohumeral joint.
The teres major muscle is a muscle of the upper limb. It attaches to the scapula and the humerus and is derived from the Latin 'teres', meaning 'rounded'. It is positioned above the latissimus dorsi muscle and assists in the extension and medial rotation of the humerus. The teres major is commonly confused as a rotator cuff muscle, but it does not attach to the capsule of the shoulder joint. The teres major muscle originates on the dorsal surface of the inferior angle and the lower part of the lateral border of the scapula. The fibres of the teres major insert into the medial lip of the intertubercular sulcus of the humerus.
The teres major is supplied by the posterior circumflex humeral artery and the thoracodorsal branch of the subscapular artery. The subscapular artery has two branches: the circumflex scapular artery and the thoracodorsal artery. This thoracodorsal artery travels inferomedially, running across the lateral angle of the scapula. The teres major is innervated by the lower subscapular nerve, derived from C5, C6, and C7 nerve roots. This nerve branches from the brachial plexus; specifically, it is the third branch of the posterior cord, giving rise to the thoracodorsal nerve before branching into the lower subscapular nerve.
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Pectoralis Minor
The pectoralis minor is a thin, triangular muscle located under the pectoralis major. Together, they form the anterior wall of the axilla. The pectoralis minor originates from the margins of the third to fifth ribs near the costal cartilages. The fibres pass upward and laterally to insert into the medial border and superior surface of the coracoid process of the scapula.
The pectoralis minor is one of the most superficial muscles on the anterior aspect of the chest or thoracic wall. It is crucial in the stabilization of the scapula by pulling it downward and anteriorly against the thoracic wall. The pectoralis minor also depresses the point of the shoulder, drawing the scapula superiorly towards the thorax and throwing its inferior angle posteriorly. This muscle also acts as an accessory muscle of inspiration. When the ribs are immobilized, the pectoralis minor brings the scapula forward.
The primary nerve supply to the pectoralis minor comes via the medial pectoral nerve, one of the minor branches of the brachial plexus that arises from the cervical portion of the spinal cord. The medial and lateral pectoral nerves penetrate the pectoralis minor muscle to innervate it. The vascular supply to the pectoralis minor comes from several sources, including the thoracoacromial artery, superior thoracic artery, and lateral thoracic artery.
A shortened pectoralis minor restricts flexion of the shoulder joint by limiting scapular rotation and preventing the glenoid cavity from attaining the cranial orientation necessary for complete flexion of the joint. This can cause "winging" of the scapula, prominence of the inferior angle, and depression of the coracoid process. It can also lead to thoracic outlet syndrome by impinging on the brachial plexus and axillary blood vessels, causing shoulder impingement.
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Serratus Anterior
The serratus anterior (SA) is a fan-shaped muscle that originates on the superolateral surfaces of the first to eighth or ninth ribs at the lateral wall of the thorax. It inserts along the superior angle, medial border, and inferior angle of the scapula. The serratus anterior is a key scapular stabiliser, keeping the shoulder blades against the ribcage at rest and during movement. It is also known as the "boxer's muscle" because it is largely responsible for the protraction of the scapula, which is the pulling of the scapula forward and around the rib cage that occurs when throwing a punch.
The serratus anterior is divided into three parts: the upper/superior, middle/intermedius, and lower/inferior. The upper section originates from the first and second ribs and inserts at the superior angle of the scapula. The middle section originates from the second and third ribs and inserts at the medial border of the scapula. The lower section, which is the most powerful and prominent part, originates from the fourth to ninth ribs and inserts at the medial border and inferior angle of the scapula.
The serratus anterior acts in concert with the upper and lower fibres of the trapezius muscle to sustain upward rotation of the scapula, which allows for overhead lifting. When the shoulder girdle is fixed, all three parts of the serratus anterior work together to lift the ribs, assisting with respiration. The muscle is supplied with oxygenated blood by the lateral thoracic artery, the superior thoracic artery, and the thoracodorsal artery.
The serratus anterior is a prime mover in scapular protraction and scapular upward rotation. It is also responsible for the anterolateral motion of the scapula, which allows for arm elevation. The serratus anterior is a crucial muscle for shoulder function, allowing for a full range of motion in the shoulder joint.
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Subscapularis
The subscapularis is a large, powerful, triangular-shaped muscle that fills the subscapular fossa and inserts into the lesser tubercle of the humerus and the front of the capsule of the shoulder joint. The subscapularis is the largest and strongest muscle of the rotator cuff, which is made up of four muscles: the subscapularis, supraspinatus, infraspinatus, and teres minor. The subscapularis is the only rotator cuff muscle that has adduction and extension functions in certain positions. It also helps prevent anterior displacement of the humerus. The muscle's primary function is the internal rotation of the humerus, and it plays an important role in shoulder joint stabilisation.
The subscapularis is a prime mover in the medial rotation of the humerus, and when the arm is raised, it pulls the humerus forward and downward. The muscle is supplied by the upper and lower subscapular nerves (C5-C6), which are branches of the posterior cord of the brachial plexus. The primary blood supply to the subscapularis muscle is the subscapular artery, a branch of the axillary artery.
The subscapularis may include up to three trigger points, with the two most common occurring near the outside edge of the muscle. Referred pain from trigger points in the subscapularis muscle concentrates in the posterior shoulder region, with spillover into the shoulder blade region and down the back of the upper arm. A unique "band" of referred pain around the wrist may also occur. An overworked subscapularis muscle may make you feel like you are not able to lift your arm. The lift-off test, also known as Gerber's Test, was originally described by Gerber and Krushell in 1991 and is the established clinical test for examining the subscapularis. Positive bear-hug and belly press tests indicate significant tearing of the subscapularis.
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Frequently asked questions
The teres major, latissimus dorsi, and pectoralis minor muscles all adduct the scapula.
The scapula is the bone that connects the clavicle to the humerus, forming the shoulder joint.
The teres major muscle performs adduction and medial rotation at the shoulder joint.
The latissimus dorsi muscle performs adduction, extension, and medial rotation at the shoulder joint.
The pectoralis minor muscle pulls the scapula forward (protraction) and down (depression).
