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The subscapularis muscle is a large, powerful, triangular shoulder muscle that is responsible for the internal rotation of the arm and stabilization of the shoulder joint. It is the largest and strongest of the four rotator cuff muscles. The subscapularis muscle is innervated by the upper and lower subscapular nerves (C5-C6), which originate from the posterior cord of the brachial plexus. The upper subscapular nerve supplies the upper part of the subscapularis, while the lower subscapular nerve branches into two, with one branch supplying the lower part of the subscapularis.
| Characteristics | Values |
|---|---|
| Shape | Triangular |
| Location | Subscapular fossa of scapula |
| Function | Internally rotates the arm on the shoulder joint |
| Innervation | Upper and lower subscapular nerves (C5-C6) |
| Blood supply | Subscapular artery, a branch of the axillary artery |
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What You'll Learn
The subscapularis is a rotator cuff muscle
The subscapularis muscle is a large and powerful triangular muscle that is located in the subscapular fossa of the scapula. It is one of four muscles that make up the rotator cuff, along with the supraspinatus, infraspinatus, and teres minor. The subscapularis is the largest and strongest muscle of the four. The rotator cuff muscles work together to stabilize and guide the humeral head within the glenoid cavity during various upper limb movements. Each muscle in the cuff also has its own specific function, and the subscapularis muscle's specific role is to internally rotate the arm on the shoulder joint.
The subscapularis muscle is innervated by the upper and lower subscapular nerves (C5-C6), which originate from the posterior cord of the brachial plexus. The upper subscapular nerve innervates the upper portion of the subscapularis muscle, while the lower subscapular nerve divides into two branches. One branch supplies the lower part of the subscapularis muscle, and the other branch supplies the teres major muscle. The subscapularis and teres major muscles are often considered a functional unit because they share the same innervation and actions.
The subscapularis muscle is a common topic in anatomy exams, and it is also frequently studied in the context of surgical procedures and imaging techniques. Its unique axis of pull, from the proximal humerus to the costal scapular surface, allows it to medially rotate the humeral head within the glenoid fossa. This muscle is less likely to tear than other rotator cuff muscles, but injuries can occur, resulting in symptoms such as pain when moving the shoulder, especially when the arm is raised above the shoulders.
The subscapularis muscle plays a crucial role in shoulder movement and stability. Its contraction results in the internal or medial rotation of the humerus. It originates at the subscapular fossa and transitions into a tendon that inserts on the lesser tubercle of the humerus in front of the joint capsule. Some of its fibres extend to the greater tubercle and bicipital groove. The subscapular artery, a branch of the axillary artery, provides the primary blood supply to the subscapularis muscle.
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It is innervated by the upper subscapular nerve
The subscapularis muscle is a large and powerful triangular muscle that is located under the scapula, in the subscapular fossa of the scapula. It is one of the four muscles that make up the rotator cuff, along with the supraspinatus, infraspinatus, and teres minor muscles. The rotator cuff muscles work together to stabilize and steer the humeral head within the glenoid cavity during movement of the upper limb.
The subscapularis muscle is innervated by the upper and lower subscapular nerves (C5-C6), which originate from the posterior cord of the brachial plexus. The upper subscapular nerve innervates the upper portion of the subscapularis muscle, while the lower subscapular nerve is responsible for innervating the lower portion. The upper subscapular nerve has a mean length of 51.4 ± 12.8 mm, and it inserts into the muscle belly close to the myotendinous junction.
The subscapularis muscle is the only medial (internal) rotator among the rotator cuff muscles. Its specific role is to internally rotate the arm on the shoulder joint, providing stability to the shoulder joint. Due to its unique axis of pull, the subscapularis muscle enables the medial rotation of the humeral head within the glenoid fossa.
The subscapularis muscle is susceptible to injuries, particularly tendonitis, which can cause pain when moving the shoulder, especially when the arm is raised above the shoulders. It is also important to note that the subscapularis muscle is at risk of iatrogenic injury during certain medical procedures, such as axillary dissection, where the thoracodorsal nerve is exposed, and any originating subscapular nerves may be vulnerable to injury.
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It is also innervated by the lower subscapular nerve
The subscapularis muscle is a large and powerful triangular muscle that is located in the subscapular fossa of the scapula. It is one of the four muscles that make up the rotator cuff, along with the supraspinatus, infraspinatus, and teres minor muscles. The rotator cuff muscles work together to stabilize and guide the humeral head within the glenoid cavity during movements of the upper limb.
The subscapularis muscle is innervated by both the upper and lower subscapular nerves (C5-C6). These nerves stem from the superior and posterior cords of the brachial plexus, respectively. The upper subscapular nerve innervates the upper portion of the subscapularis muscle, while the lower subscapular nerve has two branches. One branch of the lower subscapular nerve inserts into the lower portion of the subscapularis muscle, providing innervation to this region. The other branch of the lower subscapular nerve provides innervation to the teres major muscle.
The subscapularis muscle is at risk of iatrogenic injury during certain procedures, such as axillary dissection or shoulder arthroplasty. The upper and lower subscapular nerves insert into the muscle belly close to the myotendinous junction, making them susceptible to compression or torsional injuries. As a result, it is important to consider the variability of the branching pattern of the subscapular nerve and the presence of accessory nerves during surgical procedures to avoid nerve damage.
The subscapularis muscle plays a crucial role in the internal rotation of the arm and stabilization of the shoulder joint. It is the largest and strongest muscle of the rotator cuff, and its unique axis of pull allows it to medially rotate the humeral head within the glenoid fossa. The primary blood supply to the subscapularis muscle is provided by the subscapular artery, a branch of the axillary artery.
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The subscapular nerves originate from the brachial plexus
The subscapularis is a rotator cuff muscle that is responsible for the internal rotation of the arm and stabilization of the shoulder joint. It is a triangular shoulder muscle located in the subscapular fossa of the scapula. It attaches between the scapula and the proximal humerus.
The subscapularis muscle is innervated by two distinct nerve branches, the upper and lower subscapular nerves (C5-C6). These nerves stem from the superior and posterior cords of the brachial plexus, respectively. The upper subscapular nerve innervates the cranial half of the muscle, while the lower subscapular nerve bifurcates into two branches. One branch supplies the lower part of the subscapularis, and the other branch inserts into the teres major.
The subscapular nerves are part of a group of nerves that innervate the muscles that move the scapula. Due to the unique axis of pull of the subscapularis, from the proximal humerus to the costal scapular surface, the subscapularis medially rotates (internal rotation) the humeral head within the glenoid fossa. The subscapular nerve is at risk of iatrogenic injury, and its integrity is critical for the successful healing of the subscapularis during anatomic total shoulder arthroplasty surgery.
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The subscapularis muscle is the largest and strongest of the rotator cuff muscles
The subscapularis muscle is a large and powerful triangular muscle that is located in the subscapular fossa of the scapula. It is the largest and strongest of the four rotator cuff muscles, which also include the supraspinatus, infraspinatus, and teres minor muscles. The subscapularis muscle is responsible for the internal rotation of the arm and stabilization of the shoulder joint. It is also involved in adducting the humerus and maintaining glenohumeral joint stability.
The subscapularis muscle is innervated by the upper and lower subscapular nerves, which originate from the posterior cord of the brachial plexus. The brachial plexus is formed by the ventral rami of the lower cervical and upper thoracic nerve roots. These ventral rami combine to form the upper, middle, and lower trunks, which further divide into anterior and posterior divisions. The posterior divisions then form three cords, including the posterior cord, from which the subscapular nerves arise.
The upper subscapular nerve innervates the upper portion of the subscapularis muscle, while the lower subscapular nerve has two branches. One branch of the lower subscapular nerve supplies the lower part of the subscapularis muscle, and the other branch supplies the teres major muscle. The subscapular nerves are at risk of iatrogenic injury due to their insertion in the muscle belly close to the myotendinous junction.
The subscapularis muscle receives its blood supply primarily from the subscapular artery, a branch of the axillary artery. The axillary artery itself is a continuation of the subclavian artery. The subscapular nerve provides important sensory and motor functions to the subscapularis muscle, allowing for the coordination of movements and the detection of stimuli in the surrounding area.
In summary, the subscapularis muscle is the largest and strongest of the rotator cuff muscles, with a crucial role in shoulder movement and stability. Its innervation by the upper and lower subscapular nerves contributes to its function and highlights the complexity of the human muscular system.
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Frequently asked questions
The subscapularis muscle is innervated by the upper and lower subscapular nerves (C5-C6), which come from the posterior cord of the brachial plexus.
The brachial plexus is formed by the ventral rami of the lower four cervical and the upper thoracic nerve roots. These ventral rami fuse to build an upper, middle, and lower trunk, which subsequently split into anterior and posterior divisions and then three cords.
The subscapularis muscle is responsible for internal rotation and stabilization of the shoulder joint. It is the largest and strongest part of the four rotator cuff muscles.
