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The scapula, or shoulder blade, is a flat, triangular bone that sits above the rib cage in the upper back. It connects with the humerus and clavicle to form the shoulder joint. The scapula can move in six directions, and each movement is produced by specific primary muscles. The muscles that attach to the scapula are essential for the arm's wide range of movement and mobility. The scapula's stability is dependent on the surrounding musculature, with several muscles that attach directly to it. So, which muscles retract the scapula?
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What You'll Learn
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 is divided into three parts: Upper/Superior, Middle/Intermedius, and Lower/Inferior. The Upper/Superior part extends from the first to the second rib and connects to the superior angle of the scapula. The Middle/Intermedius part extends from the second to the third rib and connects to the medial border of the scapula. The Lower/Inferior part, which is the most powerful and prominent, extends from the fourth to the ninth rib and connects to the medial border and inferior angle of the scapula.
The Serratus Anterior is a key scapula stabilizer, playing a crucial role in keeping the shoulder blades against the ribcage, both at rest and during movement. It acts as the prime mover in scapular protraction and scapular upward rotation, allowing for anteversion and protraction of the arm. This muscle is also known as the "boxer's muscle" because it is responsible for the protraction of the scapula, or the pulling of the scapula forward and around the rib cage, which occurs when throwing a punch.
The Serratus Anterior is vulnerable to pain and injury, especially in sports with repetitive motions such as swimming, tennis, or weightlifting. Serratus Anterior muscle pain may be caused by tension, stress, or overuse. A rare condition called Serratus Anterior Myofascial Pain Syndrome (SAMPS) can also cause pain in this muscle. When the Serratus Anterior is inhibited, lengthened, or weakened, scapular protraction and upward rotation can be impaired, leading to a condition called scapula winging.
The Serratus Anterior has a well-defined development process, starting as a muscular column in the embryonic stage and gradually differentiating into a broad and flat muscle that attaches to the scapula. The vascular supply to this muscle includes the lateral thoracic artery, the superior thoracic artery, and the thoracodorsal artery. The long thoracic nerve, which arises from the upper portion of the superior trunk of the brachial plexus, is responsible for its innervation.
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Rhomboids
The rhomboids are a group of deep intrinsic shoulder muscles that are important for upper limb movement and scapular stability. They are made up of two muscles: the rhomboid major and the rhomboid minor. These muscles are located in the upper back, under the trapezius muscle, and are responsible for facilitating scapular retraction, elevation, and rotation. They also play a role in keeping the scapula in position at the posterior thoracic wall.
The rhomboid minor is a cylindrical muscle that originates at the ligamentum nuchae and C7 and T1 vertebra. It inserts at the medial border of the scapula, near the base of the spine of the scapula. The rhomboid major, on the other hand, is a quadrangular muscle located just below the rhomboid minor. Its origin is from the spinous processes of the T2-T5 vertebra, and it inserts on the medial border of the scapula, inferior to the rhomboid minor.
The motor function of the rhomboid muscles is controlled by the dorsal scapular nerve (DSN), which arises from the ventral ramus of the spinal nerve root C5. The DSN courses posteriorly through the middle scalene muscles and provides innervation to the levator scapulae and serratus posterior superior muscles. The rhomboid muscles receive their vascular supply primarily through the dorsal scapular artery (DSA), which generally arises from the second or third portion of the subclavian artery.
The rhomboids work in conjunction with other muscles such as the levator scapulae, serratus anterior, trapezius, and pectoralis muscles to form the shoulder girdle and stabilize the scapula. They help anchor the scapula and prevent "winging," which can occur due to dysfunction, weakness, or loss of nerve function in the rhomboids. The rhomboids are also vital for actions such as pulling and are engaged during throwing and overhead arm movements.
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Trapezius
The trapezius muscle is a large, thin, triangular muscle that spans the upper back. It is the most superficial of the extrinsic muscles of the back and is found in the posterior cervical and upper back regions. It originates from the superior nuchal line and external occipital protuberance, the ligamentum nuchae, the seventh cervical vertebra, and all the thoracic vertebrae. The trapezius has three functional parts: the descending (upper) part, composed of superior fibres; the transverse (middle) part, composed of middle fibres; and the ascending (lower) part, composed of inferior fibres.
The descending part of the trapezius muscle forms the anterior boundary of the posterior cervical region and the posterior boundary of the lateral cervical region. The ascending part of the trapezius muscle forms the superomedial boundary of the triangle of auscultation. The fibres of the ascending part of the trapezius muscle travel superolaterally along the upper back and converge to a tendon, which inserts onto the medial half of the spine of the scapula.
The trapezius muscle helps facilitate many different movements, including shrugging the shoulders, scapular depression, and scapular retraction. It is crucial for proper scapula positioning and plays an important role in the shoulder. The main function of the trapezius is stabilizing the scapula in its anatomical place, as well as controlling it during movements of the shoulder and upper limb.
The arterial supply to the trapezius varies depending on the level. The descending part of the muscle is supplied by transverse muscular branches arising from the occipital artery, which passes along the deep surface of the muscle. The transverse part is supplied by the superficial cervical artery or a branch from the transverse cervical artery. The ascending part is supplied by muscular branches of the dorsal scapular artery, which arises from the subclavian artery.
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Pectoralis Minor
The pectoralis minor is a thin, flat muscle found underneath the pectoralis major. It is one of two pectoral muscles, and it is the smaller of the two. The pectoralis minor is triangular in shape and plays a crucial role in the stabilization of the scapula, or shoulder blade.
The pectoralis minor extends from the third, fourth, and fifth ribs on each side of the rib cage to the coracoid process of the scapula. The origins of the muscle are all lateral to the costal cartilages. The primary actions of this muscle include the stabilization, depression, abduction or protraction, upward tilt, and downward rotation of the scapula. When the ribs are immobilized, the pectoralis minor brings the scapula forward, and when the scapula is fixed, it lifts up the rib cage.
The pectoralis minor works with the serratus anterior muscle to create a full range of movement for the scapula. The serratus anterior, also known as the "boxer's muscle", is a key scapula stabilizer that helps keep the shoulder blade against the rib cage at all times.
The pectoralis minor is an important muscle involved in scapular retraction, along with the pectoralis major, deltoid, and serratus anterior muscles. These muscles function to internally rotate the shoulder and bring the arms across the body.
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Pectoralis Major
The pectoralis major is the foremost and largest muscle of the chest. It is a fan-shaped muscle that arises from parts of the clavicle, sternum, and costal cartilages of the true ribs. The pectoralis major is divided into three parts: the clavicular part, the sternocostal part, and the abdominal part. All three parts converge laterally and insert onto the greater tubercle of the humerus. The clavicular part originates from the anterior surface of the medial half of the clavicle, while the sternocostal part originates from the anterior surface of the sternum and the anterior aspects of the costal cartilages of ribs 1-6. The abdominal part, the smallest of the three, originates from the anterior layer of the rectus sheath.
The pectoralis major is a prominent chest muscle that acts mainly on the shoulder joint. Its primary functions are flexion, adduction, and internal rotation of the humerus. It adducts and rotates the arm at the glenohumeral joint, and the clavicular part helps to flex the extended arm up to 90 degrees. The pectoralis major is innervated by the lateral and medial pectoral nerves, which stem from the brachial plexus. It receives dual motor innervation by the medial pectoral nerve and the lateral pectoral nerve, also known as the lateral anterior thoracic nerve.
The pectoralis major is a common muscle for gym-goers and is often referred to as the "pecs" muscle. It is a strong adductor and internal rotator of the humerus at the shoulder joint. The pectoralis major may also be referred to as the "chest muscle" as it is the largest and most superficial muscle in the chest area. In males, it is covered by the deep layer of fascia, subcutaneous tissue, and the adjacent skin, while in females, it is covered by the breast.
Tears of the pectoralis major are rare but can occur in high-impact contact sports such as powerlifting. Most lesions are located at the musculotendinous junction and result from violent, eccentric contraction of the muscle, such as during a bench press. Treatment for tears involves surgical excision, followed by immobilization of the affected arm in a sling for about six to eight weeks. Physical therapy is typically introduced two months after surgery, followed by muscle strengthening after six months.
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Frequently asked questions
The muscles that retract the scapula are the rhomboids and middle trapezius.
The rhomboids are a muscle group that is responsible for facilitating scapular retraction. They make up part of the shoulder girdle and are important for the movement of the upper extremity and overall stabilization of the shoulder.
The trapezius muscle is a large muscle that spreads across the entire back. It helps facilitate many different movements like shrugging the shoulders, scapular depression, and scapular retraction.
Yes, other important muscles involved in scapular retraction include the pectoralis major, pectoralis minor, deltoid, and serratus anterior muscles.
