Nameenter Your Namekine 3200asynchronous Assignment 4label Lines 1 Th
Enter Your Name KINE 3200 Asynchronous Assignment 4 Label lines 1 through 6 on the image below with an action from the list below that corresponds with movements of the shoulder girdle indicated by the arrow. Adduction (retraction), Abduction (protraction), Depression, Elevation, Rotation, Downward Rotation, Upward Rotation. On the lines below, which correspond to the numbers of the arrows above, list the muscle(s) or parts of muscles responsible for causing each movement. For each muscle listed, include the origin and the insertion.
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The shoulder girdle, also known as the pectoral girdle, is a complex structure consisting of bones, muscles, and joints that facilitate a wide range of movements essential for regular arm and shoulder mobility. The movements of the shoulder girdle include retraction, protraction, elevation, depression, rotation, upward rotation, and downward rotation. Each movement is primarily driven by specific muscles, with action depending on the points of origin and insertion that enable the movement at the scapulothoracic joint.
Movement 1: Retraction (Adduction)
The primary muscle responsible for scapular retraction is the rhomboid major and minor. These muscles originate from the vertebral border of the scapula and insert onto the spinous processes of the cervical and thoracic vertebrae. They work to pull the scapula medially towards the spine, allowing the shoulder blades to come closer together. The rhomboids are crucial during movements where the scapula must be pulled back, as in rowing or pulling actions.
Rhomboid Major and Minor
Origin: Spinous processes of C7-T5 (rhomboid minor), T2-T5 (rhomboid major)
Insertion: Medial border of the scapula
Movement 2: Protraction (Abduction)
The main muscle facilitating protraction is the serratus anterior. This muscle originates from the outer surfaces of the upper 8 or 9 ribs and inserts onto the anterior surface of the medial border of the scapula. When the serratus anterior contracts, it pulls the scapula forward around the thoracic cage, allowing the arm to reach forward.
Serratus Anterior
Origin: External surfaces of first to eighth or ninth ribs
Insertion: Anterior surface of the medial border of the scapula
Movement 3: Depression
The scapula depression is primarily performed by the lower fibers of the trapezius and the serratus anterior. The lower trapezius originates from the spinous processes of the middle and lower thoracic vertebrae and inserts onto the spine of the scapula and clavicle, pulling the scapula downward. The serratus anterior also assists in depression by pulling the medial border downward and anteriorly.
Lower Trapezius
Origin: Spinous processes of T5–T12
Insertion: Spinal acromion and spine of scapula
Serratus Anterior
Origin: External surfaces of upper 8 or 9 ribs
Insertion: Anterior surface of medial border of scapula
Movement 4: Elevation
The elevation of the scapula involves the upper fibers of the trapezius and the levator scapulae. The trapezius originates from the occipital bone and the spinous processes of C7-T12, descending to insert on the lateral third of the clavicle, acromion, and spine of the scapula. The levator scapulae originates from the transverse processes of the first four cervical vertebrae and inserts onto the superior angle of the scapula. Both muscles contribute to lifting the scapula upwards.
Upper Trapezius
Origin: External occipital protuberance, medial superior nuchal line, ligamentum nuchae
Insertion: Lateral third of clavicle and acromion
Levator Scapulae
Origin: Transverse processes of C1-C4
Insertion: Superior angle of the scapula
Movement 5: Rotation
Scapular rotation, necessary for raising the arm overhead, involves the serratus anterior and trapezius. When the upper and lower fibers of the trapezius and serratus anterior work together, they rotate the scapula upward. The serratus anterior, originating from the ribs and inserting onto the medial border of the scapula, plays a pivotal role, especially during overhead activities.
Serratus Anterior
Origin: External surfaces of ribs 1-9
Insertion: Costal surface of the medial border of the scapula
Upper and Lower Trapezius
Originate from the occipital bone, C7-T12 spinous processes, and insert onto the acromion and spine of scapula
Movement 6: Downward Rotation
The downward rotation of the scapula is mainly controlled by the rhomboid muscles and levator scapulae. The rhomboids originate from the cervical and upper thoracic vertebrae and insert onto the medial border of the scapula, pulling the scapula downward and medially. The levator scapulae, originating from C1-C4 transverse processes, inserts onto the superior angle of the scapula to elevate and downwardly rotate the scapula.
Rhomboid Major and Minor
Origin: Spinous processes of C7-T5
Insertion: Medial border of scapula
Levator Scapulae
Origin: Transverse processes of C1-C4
Insertion: Superior angle of scapula
Conclusion
Understanding the musculature responsible for the various movements of the shoulder girdle is essential for both clinical assessment and designing effective rehabilitation programs. The coordinated activity of muscles like the trapezius, serratus anterior, rhomboids, and levator scapulae enables complex movements essential for daily tasks and athletic performance. Their origins and insertions facilitate their actions, allowing precise movement control and stability of the shoulder complex.
References
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