Maximus Gage
The scapula, or shoulder blade, is a triangular, flat bone that serves as an attachment site for 17 muscles. These muscles include the rhomboids major and minor, the serratus anterior, the subscapularis, the infraspinatus, the supraspinatus, the teres major and minor, the levator scapulae, the deltoid, the latissimus dorsi, the trapezius, the pectoralis minor, the coracobrachialis, and the long head of the biceps brachii and triceps. The scapula articulates with the posterior chest wall and moves in conjunction with the upper limb via the scapulothoracic joint, allowing for a full range of motion in the arm.
| Characteristics | Values |
|---|---|
| Number of muscles attached to the scapula | 17 |
| Muscles attached to the scapula | Deltoid, Latissimus Dorsi, Trapezius, Serratus Anterior, Biceps Brachii, Coracobrachialis, Pectoralis Minor, Triceps, Levator Scapulae, Rhomboid Major, Rhomboid Minor, Teres Major, Teres Minor, Supraspinatus, Infraspinatus, Subscapularis, Pectoralis Major |
| Function of the scapula | Stabilization of the glenohumeral joint, scapulo-humeral coordination, and full-functional upper extremity movement |
| Nerves to the scapula | Dorsal scapular, upper and lower subscapular, and suprascapular nerves |
| Arteries to the scapula | Suprascapular artery, posterior circumflex humeral artery, circumflex scapular artery, transverse cervical artery |
| Bursae | Scapulothoracic and subscapularis |
| Fracture incidence | Uncommon, indicating severe trauma |
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What You'll Learn
- The scapula is a flat, triangular bone that serves as an attachment site for 17 muscles
- The bone is well-protected, so scapular fractures are rare and indicate severe trauma
- The serratus anterior, levator scapulae, and rhomboid muscles are among those attached to the scapula
- The scapula moves in six ways, allowing for full upper extremity movement
- The scapulothoracic joint is where the scapula smoothly glides over the chest wall
The scapula is a flat, triangular bone that serves as an attachment site for 17 muscles
The scapula, or shoulder blade, is a flat, roughly triangular bone that lies on the posterior surface of the thorax, over the ribs 2-7. It is part of the pectoral (shoulder) girdle, connecting the humerus (upper arm bone) with the clavicle (collar bone). The scapula has three borders (superior, medial, and lateral) and three angles (superior, inferior, and lateral). Its stability is dependent on the surrounding musculature, with 17 muscles in total that attach to it. These include the muscles that stabilise the shoulder joint (rotator cuff muscles) and those whose primary function is to provide it with movement.
The front of the scapula (also known as the costal or ventral surface) has a broad concavity called the subscapular fossa, to which the subscapularis muscle attaches. The medial two-thirds of the fossa have three longitudinal oblique ridges, and another thick ridge adjoins the lateral border. The ridges give attachment to the tendinous insertions, and the surfaces between them to the fleshy fibres of the subscapularis muscle. The subscapularis arises from the anterior surface of the scapula, also known as the subscapular fossa. The posterior surface of the scapula features a prominent ridge called the spine of the scapula, which divides the surface into two unequal parts: the supraspinous fossa and infraspinous fossa. The supraspinatus attaches to the superior portion of the posterior side (the supraspinous fossa), while the infraspinatus attaches to the posterior surface (the infraspinous fossa).
The deltoid arises from the lower border of the crest of the spine and from the lateral border of the acromion. The levator scapulae attaches at the superior angle of the scapula, while the teres major attaches at the inferior angle of the scapula. The rhomboids major and minor attach to the medial border of the scapula, whereas the serratus anterior attaches to the medial margin. The long head of the biceps brachii arises from the supraglenoid tubercle, and the short head from the lateral part of the tip of the coracoid process. The coracobrachialis arises from the medial part of the tip of the coracoid process. The pectoralis minor is inserted into the medial border and superior surface of the coracoid process. The long head of the triceps arises from the infraglenoid tubercle.
The scapula performs elevation of the acromion process during a throwing or serving motion to avoid impingement of the rotator cuff tendons. It articulates with the posterior chest wall and is connected to the upper limb by the acromioclavicular joint. The scapulothoracic joint movement is dependent on the acromioclavicular and sternoclavicular joints. The scapulohumeral rhythm is a combination of motions of the scapula, clavicle, and humerus to achieve full elevation of the arm, with a 2:1 ratio. This means that for every two degrees of movement at the humerus, the scapula moves one degree.
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The bone is well-protected, so scapular fractures are rare and indicate severe trauma
The scapula is a triangular, flat bone that serves as an attachment site for many muscles. It is a crucial component of the shoulder joint, facilitating six types of motion that enable full functional upper extremity movement. These motions include protraction, retraction, elevation, depression, upward rotation, and downward rotation. The scapula's stability is dependent on the surrounding musculature, with several muscles attaching directly to it.
The bone is well-protected by the rib cage and thoracic cavity anteriorly and is covered with a significant amount of soft tissue, including muscles, posteriorly. Due to this protection, scapular fractures are rare, accounting for only 0.5 to 1% of all fractures. When they do occur, scapular fractures are indicative of severe trauma, such as high-impact road collisions, crushing injuries, or sports injuries. The injury is often associated with other severe or life-threatening conditions, which can delay the diagnosis and treatment of the fracture.
The scapula has various bony projections and landmarks that serve as attachment sites for muscles, ligaments, and other soft tissues. For example, the levator scapulae attaches at the superior angle of the scapula, while the teres major attaches at the inferior angle. The scapula also provides attachment points for ligaments connecting the acromion and coracoid process to the clavicle. These ligaments can be injured during falls or traumatic impacts to the shoulder, resulting in shoulder separation.
The scapula is associated with several important nerves, including the dorsal scapular, upper and lower subscapular, and suprascapular nerves, which arise from different parts of the brachial plexus. The scapula is also related to various muscles, including both intrinsic and extrinsic muscles. The intrinsic muscles attach directly to the bone and include the four members of the rotator cuff: the supraspinatus, infraspinatus, subscapularis, and teres minor. These muscles form a musculotendinous cuff around the glenohumeral joint, providing stability and supporting rotational movements. The extrinsic muscles, such as the triceps, biceps, and deltoid, attach to the processes of the scapula and affect motion at the glenohumeral joint.
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The serratus anterior, levator scapulae, and rhomboid muscles are among those attached to the scapula
The scapula is a sturdy, flat, triangular bone that provides attachment to several groups of muscles. The serratus anterior, levator scapulae, and rhomboid muscles are among those attached to the scapula.
The serratus anterior is a muscle of the chest. It originates from the upper eight or nine ribs and inserts along the entire length of the anterior aspect of the medial border of the scapula. It pulls the scapula forward around the thorax, which is essential for arm anteversion. The serratus anterior is also involved in respiration, as it can lift the ribs when the shoulder girdle is fixed. This muscle is occasionally called the "big swing muscle" or "boxer's muscle" due to its role in the protraction of the scapula.
The levator scapulae attaches at the superior angle of the scapula. It is one of the muscles responsible for scapular elevation. The levator scapulae also works in conjunction with the rhomboid muscles to elevate and retract the scapula.
The rhomboids consist of two muscles: the rhomboid major and rhomboid minor. They lie deep to the trapezius, forming parallel bands that pass from the vertebrae to the medial border of the scapula. These muscles retract, elevate, and rotate the scapula, as well as protracting the medial border to keep it in position at the posterior thoracic wall. The rhomboids are important for upper limb movement and stability of the shoulder girdle and scapula. They receive innervation from the dorsal scapular nerve and are supplied by the dorsal scapular artery.
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The scapula moves in six ways, allowing for full upper extremity movement
The scapula is a bone that forms part of the shoulder joint. It is a critical component of the shoulder and is responsible for the full range of motion of the upper extremity. The scapula moves in six ways: protraction, retraction, elevation, depression, upward rotation, and downward rotation.
Protraction is accomplished by the actions of the serratus anterior, pectoralis major, and pectoralis minor muscles. Retraction, on the other hand, is accomplished by the actions of the trapezius, rhomboids, and latissimus dorsi muscles. For the scapula to achieve elevation, the trapezius, levator scapulae, and rhomboid muscles work together.
Depression, the fourth type of movement, is caused by the force of gravity and the actions of several muscles, including the latissimus dorsi, serratus anterior, pectoralis major and minor, and the trapezius muscles. The fifth type of movement, upward rotation, is accomplished by the trapezius and serratus anterior muscles. Finally, downward rotation is caused by the force of gravity, along with the actions of the latissimus dorsi, levator scapulae, rhomboids, and the pectoralis major and minor muscles.
The scapula is also involved in scapulohumeral rhythm, which is a combination of motions of the scapula, clavicle, and humerus to achieve full elevation of the arm. This rhythm has a 2:1 ratio, meaning for every two degrees of movement at the humerus, the scapula moves one degree. To achieve the full 180 degrees of arm elevation, 120 degrees of movement occur at the glenohumeral joint, and 60 degrees of upward rotation occurs at the scapulothoracic joint.
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The scapulothoracic joint is where the scapula smoothly glides over the chest wall
The scapula is a bone that plays an important role in the function of the shoulder joint. It is attached to the chest wall by the acromioclavicular and sternoclavicular joints. The scapula is not a true anatomical joint, but rather a unit that gathers these two joints and the junction between the anterior surface of the scapula and the thoracic cage. This junction, known as the scapulothoracic joint, enables the scapula to smoothly glide over the chest wall, allowing for a wide range of motion in the shoulder.
The scapulothoracic joint does not have specific articular surfaces, ligaments, or a joint capsule. Instead, it is characterised by the connection between the slightly concave anterior surface of the scapula and the correspondingly convex superolateral surface of the thoracic wall. These surfaces are separated by the subscapularis muscle, which fills the subscapular fossa on the anterior surface of the scapula, and the serratus anterior muscle, which attaches to the medial margin of the scapula.
The scapulothoracic joint enables three degrees of freedom in scapular movement: elevation (with a range of motion of 40 degrees), depression (with a range of motion of 10 degrees), and external rotation-internal rotation. These movements are made possible by the muscles that attach to the scapula, such as the levator scapulae, trapezius, rhomboids, and serratus anterior, which are responsible for rotational movements and stabilization of the scapula.
The scapula's stability is dependent on the surrounding musculature, with several muscles attaching directly to the bone. These include the intrinsic muscles, which attach directly to the surface of the bone and include the four members of the rotator cuff: the supraspinatus, infraspinatus, subscapularis, and teres minor. These muscles form a musculotendinous cuff around the glenohumeral joint and provide muscular support. Additionally, the extrinsic muscles of the scapula, such as the triceps, biceps, and deltoid, attach to the processes of the scapula and affect motion at the glenohumeral joint.
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Frequently asked questions
The scapular muscles are located on the scapula, or shoulder blade. The scapula is a triangular, flat bone that serves as a site for the attachment of many muscles (17 in total).
Some examples of scapular muscles include the levator scapulae, rhomboid major, rhomboid minor, serratus anterior, and pectoralis minor.
The scapular muscles assist with abduction and internal and external rotation of the glenohumeral joint. They also play a role in stabilizing the scapula and facilitating the full range of motion of the upper extremity.
