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The scapula, also known as the shoulder blade, is a flat, triangular bone located at the back of the trunk. It connects the clavicle to the humerus, forming the glenohumeral (shoulder) joint. The scapula provides attachment points for several groups of muscles, including the rotator cuff muscles, and is essential for the full range of motion of the upper extremity. Seventeen muscles attach to the scapula, including the biceps brachii, deltoid, levator scapulae, serratus anterior, and more. These muscles enable the scapula to perform various movements, such as elevation, depression, and rotation.
| Characteristics | Values |
|---|---|
| Number of muscles attached | 17 (or 18, if counting the long and short head of the biceps brachii separately) |
| Muscle groups | Intrinsic, extrinsic, and a third group including levator scapulae, trapezius, rhomboids, and serratus anterior |
| Muscle names | Biceps brachii, Coracobrachialis, Deltoid, Infraspinatus, Latissimus dorsi, Levator scapulae, Omohyoid (inferior belly), Pectoralis minor, Rhomboid major, Rhomboid minor, Serratus anterior, Subscapularis, Supraspinatus, Teres major, Teres minor, Trapezius, Triceps brachii (long head) |
| Muscle attachments | Posterior surface, scapular spine and acromion, coracoid process, glenoid cavity, supraglenoid tubercle, infraglenoid tubercle, glenoid fossa, glenohumeral joint, acromioclavicular joint, suprascapular nerve, suprascapular artery, transverse cervical artery, infraspinous fossa, spinoglenoid notch, supraspinous fossa |
| Function | Stabilization of the glenohumeral joint, abduction, external and internal rotation of the glenohumeral joint, elevation, depression, upward rotation, downward rotation, retraction (adduction), protraction (abduction) |
| Nerves | Dorsal scapular, upper and lower subscapular, and suprascapular nerves |
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What You'll Learn
- The supraspinatus, infraspinatus, teres major, and teres minor muscles attach to the posterior surface of the scapula
- The subscapularis attaches to the anterior surface of the scapula
- The biceps brachii, coracobrachialis, and pectoralis minor attach to the coracoid process
- The levator scapulae, rhomboid major, and rhomboid minor attach to the scapula's medial border
- The deltoid, latissimus dorsi, and triceps brachii attach to the scapula's inferior angle
The supraspinatus, infraspinatus, teres major, and teres minor muscles attach to the posterior surface of the scapula
The scapula, or shoulder blade, is a flat triangular bone located at the back of the trunk. It sits over the posterior surface of ribs two to seven. The scapula forms the posterior of the shoulder girdle and connects the clavicle to the humerus. The scapula provides attachment to several groups of muscles, including the intrinsic and extrinsic muscles.
The intrinsic muscles of the scapula include the rotator cuff muscles, which are the supraspinatus, infraspinatus, teres minor, and subscapularis. These muscles attach to the scapular surface and assist with abduction and external and internal rotation of the glenohumeral joint. The supraspinatus, infraspinatus, and teres minor all arise from the posterior scapula and insert into the greater tubercle of the humerus. The supraspinatus arises from the medial two-thirds of the supraspinous fossa, which is the superior portion of the posterior side of the scapula. The infraspinatus arises from the infraspinous fossa, which is also on the posterior scapula. The teres minor arises from the infraspinous fossa as well, and its distal tendinous portion runs along the lateral border of the scapular spine.
The extrinsic muscles of the scapula attach to the processes of the scapula and affect motion at the glenohumeral joint. These include the triceps, biceps, and deltoid.
The supraspinatus, infraspinatus, teres major, and teres minor muscles play important roles in the function and stability of the shoulder joint. They assist in abduction and external and internal rotation of the glenohumeral joint, helping to provide a full range of motion for the arm.
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The subscapularis attaches to the anterior surface of the scapula
The subscapularis is a large, powerful, and strong triangular shoulder muscle. It is one of the four rotator cuff muscles, along with the supraspinatus, infraspinatus, and teres minor. The subscapularis muscle is the largest, strongest, and most powerful of these four rotator cuff muscles, contributing to internal rotation strength, shoulder adduction and abduction, and active stabilization of the glenohumeral joint. It is also the only medial (internal) rotator of all the rotator cuff muscles.
The subscapularis muscle originates from the inner surface of the scapula and attaches to the lesser tuberosity of the humerus. It arises from the anterior surface of the scapula, also known as the subscapular fossa. The subscapularis muscle forms the majority of the posterior wall of the axilla, facing the contents of the axilla with its anterior surface. The serratus anterior covers its superolateral part, while the coracobrachialis and biceps brachii muscles lie over its inferomedial part.
The subscapularis muscle derives its name from its orientation under the scapula: "sub" meaning under and "scapula" meaning wing bone. It is a multipennate muscle that fills the subscapular fossa of the scapula. The subscapularis muscle starts as a wide muscle whose medial two-thirds originate from the subscapular fossa of the scapula and from several tendinous intramuscular septa at the ridges of the fossa. The muscle fibres course laterally from the costal surface of the scapula, gradually narrowing towards a round tendon that courses towards the proximal humerus.
The subscapularis muscle's primary function is internal rotation, but it can also aid in adducting the humerus. It is innervated by the subscapular nerve, which provides its blood supply. Lymph drainage flows into the axillary nodes. The subscapular artery, a branch of the axillary artery, is the primary blood supply to the subscapularis muscle.
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The biceps brachii, coracobrachialis, and pectoralis minor attach to the coracoid process
The scapula, or shoulder blade, is a flat triangular bone located at the back of the trunk. It provides attachment points for several groups of muscles, including the intrinsic and extrinsic muscles. The intrinsic muscles of the scapula include the rotator cuff muscles, while the extrinsic muscles include the triceps, biceps, and deltoid.
The biceps brachii, coracobrachialis, and pectoralis minor muscles are among the extrinsic muscles that attach to the scapula, specifically at the coracoid process. The coracoid process is a beak-like projection that extends from the superior border of the scapula. It allows for the attachment of various muscles and ligaments, including the coracobrachialis and pectoralis minor.
The coracobrachialis muscle originates from the medial part of the tip of the coracoid process. It functions to produce flexion and adduction of the arm at the shoulder joint. The biceps brachii muscle has two heads: the long head, which arises from the supraglenoid tubercle, and the short head, which originates from the apex of the coracoid process. The pectoralis minor, meanwhile, attaches to the medial border and superior surface of the coracoid process.
The relationship between these three muscles and the coracoid process has been studied, and different types of anatomical variations have been observed. In one study, three types of relationships between the coracobrachialis muscle and the short head of the biceps brachii were identified. Type I, occurring in 54% of cases, featured a common junction between the two muscles attached to a single coracoid process. Type II, accounting for 15% of cases, was characterised by independent attachments of the two muscles to the coracoid process. Type III, the most common type at 31%, exhibited two heads of the coracobrachialis muscle, with one originating from the coracoid process laterally to the short head of the biceps brachii and the other located medially.
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The levator scapulae, rhomboid major, and rhomboid minor attach to the scapula's medial border
The scapula, or shoulder blade, is a flat, sturdy, triangular bone located at the back of the trunk. It forms the posterior of the shoulder girdle and connects the clavicle to the humerus. The scapula provides attachment points for several groups of muscles, including the levator scapulae, rhomboid major, and rhomboid minor.
The levator scapulae is a muscle that originates from the dorsal aspect of the medial border of the scapula, extending from the superior angle up to the root of the spine. It plays a crucial role in the elevation and downward rotation of the scapula, allowing for full functionality of the shoulder joint.
The rhomboid muscles, consisting of the rhomboid major and rhomboid minor, are two functionally similar, bilateral, and superficial muscles located in the upper back. They originate from the spinous processes of the thoracic vertebrae and insert into the medial border of the scapula. The rhomboid minor attaches to the medial border opposite the root of the spine, while the rhomboid major attaches between the root of the spine and the inferior angle. These muscles are responsible for scapular retraction, which involves sliding the scapula superiorly and medially along the trunk. This movement helps maintain correct posture and stabilizes the scapula, providing an anchor point for the upper limb muscles to act upon.
The levator scapulae and rhomboid minor muscles are closely interconnected and enclosed by connective tissues. They form a musculoskeletal unit with predicted connections to each other and the cervical spine. This complex region may have implications for the success of certain treatments.
In summary, the levator scapulae, rhomboid major, and rhomboid minor muscles attach to the scapula's medial border and play essential roles in scapular movement, stabilization, and posture maintenance. Their functions contribute to the full range of motion of the shoulder joint, one of the most mobile and versatile joints in the human body.
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The deltoid, latissimus dorsi, and triceps brachii attach to the scapula's inferior angle
The scapula, or shoulder blade, is a flat, triangular bone located at the back of the trunk, forming the posterior of the shoulder girdle. The scapula connects the clavicle to the humerus, and it is a critical component of the shoulder joint. The scapula provides attachment points for several muscles, including the deltoid, latissimus dorsi, and triceps brachii, which attach to the scapula's inferior angle.
The deltoid is an extrinsic muscle of the scapula, arising from the lower border of the crest of the spine and the lateral border of the acromion. It is responsible for the abduction, external rotation, and internal rotation of the glenohumeral joint. The deltoid is an important muscle for shoulder movement, as evidenced by its role in conditions like fascioscapulohumeral dystrophy, where it is the only muscle capable of moving the shoulder when scapular winging occurs.
The latissimus dorsi is another extrinsic muscle that originates from the inferior angle of the scapula. This muscle performs a variety of actions, including adduction, extension, and medial rotation at the shoulder joint. The latissimus dorsi is innervated by the thoracodorsal nerve, and its paralysis can lead to an inability to actively depress the shoulder. Additionally, the latissimus dorsi contributes to the scapulohumeral rhythm, which is the combination of motions of the scapula, clavicle, and humerus required for the full elevation of the arm.
The triceps brachii muscle, specifically its long head, originates from the infraglenoid tubercle on the lateral border, inferior to the glenoid cavity. It is responsible for elbow extension and is innervated by the radial nerve. The triceps are also considered extrinsic muscles of the scapula.
The scapula's stability is dependent on the surrounding musculature, and these three muscles—the deltoid, latissimus dorsi, and triceps brachii—play a crucial role in maintaining the scapula's position and function. The inferior angle of the scapula, where these muscles attach, is a critical anatomical landmark that allows for the protraction, retraction, elevation, depression, upward rotation, and downward rotation of the scapula, enabling the full function of the shoulder joint.
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Frequently asked questions
Seventeen muscles attach to the scapula, including the biceps brachii, coracobrachialis, deltoid, infraspinatus, latissimus dorsi, levator scapulae, omohyoid, pectoralis minor, rhomboid major, rhomboid minor, serratus anterior, subscapularis, supraspinatus, teres major, teres minor, trapezius, and triceps brachii.
The intrinsic muscles of the scapula include the rotator cuff muscles, teres major, subscapularis, teres minor, and infraspinatus. The extrinsic muscles include the triceps, biceps, and deltoid. The third group of muscles includes the levator scapulae, trapezius, rhomboids, and serratus anterior.
The muscles that attach to the scapula allow it to perform six movements: elevation, depression, upward rotation, downward rotation, retraction (adduction), and protraction (abduction).
The scapula, also known as the shoulder blade, is a flat triangular bone located at the back of the trunk. It connects the clavicle to the humerus and forms the posterior of the shoulder girdle. The scapula provides attachment to several groups of muscles, allowing for a full range of motion in the upper extremity.
