Maximus Gage
The scapula, or shoulder blade, is a sturdy, flat, triangular bone that sits above the rib cage in the upper back. It can move in six directions, including protraction, retraction, elevation, depression, and internal/external rotation, as well as upward/downward rotation. The levator scapulae, a muscle that originates from the posterior tubercles of the transverse processes of cervical vertebrae 1–4, is responsible for elevating the scapula and rotating it downward. Other muscles that contribute to the downward rotation of the scapula include the latissimus dorsi, rhomboids, and the pectoralis major and minor muscles.
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What You'll Learn
The levator scapulae
The main function of the levator scapulae is to elevate and retract the shoulder girdle at the scapulothoracic joint. It does this by tilting the glenoid cavity inferiorly, which results in a downward rotation of the scapula. This downward rotation of the scapula can also be described as a posterior tilt. The levator scapulae also acts with the trapezius, latissimus dorsi, rhomboids, pectoralis major, and pectoralis minor muscles to stabilize the spine and extend and laterally flex the neck.
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Latissimus dorsi
The latissimus dorsi is a large, flat muscle that stretches across the back and is commonly known as the
The latissimus dorsi is innervated by the sixth, seventh, and eighth cervical nerves through the thoracodorsal nerve (a long subscapular nerve). It is supplied predominantly by the thoracodorsal artery, a continuation of the subscapular artery, which is a branch of the third part of the axillary artery. The latissimus dorsi also receives blood supply from the dorsal perforating branches of the inferior three posterior intercostal arteries and the superior three lumbar arteries.
The latissimus dorsi has a synergistic role in the extension and lateral flexion of the lumbar spine. It assists as a muscle of both forced expiration and as an accessory muscle of inspiration. The muscle is also active during deep inspiration and with forceful respiratory functions such as coughing and sneezing.
The latissimus dorsi crosses the inferior angle of the scapula. A study found that, of 100 cadavers dissected, 43% had a substantial amount of fibres in the latissimus dorsi originating from the scapula. The latissimus dorsi can pull the inferior angle of the scapula in various directions, producing movements on the shoulder joint, including internal rotation, adduction, and extension of the arm.
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Pectoralis major and minor
The pectoralis major and minor muscles are two of the most superficial muscles on the anterior aspect of the chest or thoracic wall. The pectoralis minor is deep to the pectoralis major, which almost completely covers it. The pectoralis minor takes its origin from the anterior surface of the third, fourth, and fifth ribs, specifically from the margins adjacent to their costochondral junctions—the points where the bony part of the rib meets the cartilage that connects the ribs to the breastbone, or sternum. The pectoralis minor is important clinically and as a surgical landmark due to the structures that lie below or deep to the muscle and its tendon.
The pectoralis minor is also used as a reference point for the three divisions of the axillary artery. The medial pectoral nerve (C8, T1), a minor branch of the brachial plexus, provides the pectoralis minor's primary nerve supply. The nerve arises from the cervical portion of the spinal cord. The pectoralis minor's blood supply is primarily from the thoracoacromial artery, which runs along the upper chest and originates from the second part of the axillary artery.
The fibres of the pectoralis minor ascend superolaterally, angling upward and sideways toward the shoulder. The fibres eventually converge to form a flat tendon that inserts onto the coracoid process of the scapula. The coracoid process is a small hook-like structure that projects anteriorly from the superior aspect of the scapula. The pectoralis minor attaches to the medial border and superior surface of the coracoid process.
The pectoralis minor is one of the muscles that produces various movements of the scapula, also known as the shoulder blade. The scapula can move in six directions, including protraction, retraction, elevation, depression, anterior/posterior tilt, and internal/external and upward/downward rotation. The pectoralis minor primarily contributes to movements of the shoulder girdle, and it also aids in the process of respiration as a secondary action.
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Rhomboids
The rhomboids are a group of muscles formed by the rhomboid major and minor. They are deep intrinsic shoulder muscles that lie underneath the trapezius muscle. 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 is a quadrangular or diamond-shaped muscle located inferior to the rhomboid minor. It originates from the spinous processes of the T2-T5 vertebrae and inserts onto the lower portion of the medial border of the scapula.
The rhomboids receive their vascular supply from the dorsal scapular artery and innervation from the dorsal scapular nerve. They play an important role in upper limb movement and stability of the shoulder girdle and scapula. The main action of the rhomboids is scapular retraction, which involves sliding the scapula superiorly and medially along the trunk. This movement rotates the glenoid cavity inferiorly, resulting in downward rotation of the scapula. The rhomboids also work with the levator scapulae to elevate and retract the scapula, and they help to prevent scapular winging.
The rhomboids are crucial for maintaining correct posture when sitting, standing, and walking. They help to oppose excessive scapular protraction, fixing and stabilising the scapula into position. Poor upper body posture can lead to pain in the upper back, especially along the medial border of the scapulae. Strengthening the rhomboids can help relieve this pain and improve posture. Additionally, the rhomboids can be targeted in physical therapy to improve shoulder stability and range of motion.
In summary, the rhomboid muscles, particularly the rhomboid major, play a significant role in scapular movement and stability. They contribute to downward rotation of the scapula through their retracting action and work synergistically with other muscles to maintain proper scapular positioning and function.
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Force of gravity
The scapula, or shoulder blade, is a sturdy, flat, triangular bone that sits above the rib cage in the upper back. It connects the clavicle to the humerus, forming the posterior of the shoulder girdle. The scapula can move in six directions, including protraction, retraction, elevation, depression, anterior/posterior tilt, and internal/external rotation.
Downward rotation of the scapula is one of the primary movements of this bone. This motion is accomplished by a combination of muscular contractions and the force of gravity acting on the scapula. Specifically, the muscles involved in downward rotation include the latissimus dorsi, levator scapulae, rhomboids, pectoralis major, and pectoralis minor.
The latissimus dorsi muscle is a large, flat muscle that originates from the lower back and attaches to the humerus. It plays a crucial role in various shoulder movements, including adduction, extension, and internal rotation. During downward rotation of the scapula, the latissimus dorsi contracts and pulls the scapula downward and backward.
The levator scapulae muscle, as the name suggests, is responsible for elevating the scapula. It originates from the cervical vertebrae and inserts along the medial border of the scapula. While its primary function is scapular elevation, it also contributes to downward rotation by tilting the glenoid cavity inferiorly.
The rhomboids, consisting of the rhomboid major and rhomboid minor muscles, are located in the upper back between the scapula and the spine. They play a key role in stabilizing the scapula and retracting the shoulder blades. During downward rotation, the rhomboids contract and help pull the scapula downward and medially.
The pectoralis major and pectoralis minor muscles are also involved in downward scapular rotation. The pectoralis major is a thick, fan-shaped muscle that originates from the sternum and attaches to the humerus. It is primarily responsible for shoulder flexion and adduction. Meanwhile, the pectoralis minor is a thin, triangular muscle located beneath the pectoralis major. It originates from the ribs and attaches to the coracoid process of the scapula. Both muscles contribute to the downward rotation of the scapula by pulling it anteriorly and medially.
It is important to note that while gravity plays a role in downward rotation, it is the coordinated contractions of these muscles that primarily drive this movement. The force of gravity acts on the scapula, influencing its position and movement, but the specific muscles mentioned above are the primary initiators and controllers of the downward rotation of the scapula.
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Frequently asked questions
The muscles responsible for downwardly rotating the scapula are the latissimus dorsi, levator scapulae, rhomboids, and the pectoralis major and minor muscles.
The scapula, commonly referred to as the shoulder blade, is the sturdy, flat, triangular bone that connects the clavicle to the humerus.
The scapula can move in six directions: protraction, retraction, elevation, depression, anterior/posterior tilt, and internal/external and upward/downward rotation.
