|Trapezius||Upper fibres-base of skull,occipital protuberance.Ligament of neck:Middle fibres-spine of 7th cervical and upper 3 thoracic vertebrae.
Lower fibres-spines of 4th through 12th thoracic vertebrae.
|Upper fibres –posterior aspect of the outer 3rd of the clavicle.Middle fibres- upper border of the acromion process.Lower fibres – triangular space at the base of the spine.||Upper fibres- Elevation of the scapula.Middle fibres – Adduction of the scapula.Lower fibres – Depression, adduction, and
Upward rotation of the scapula.
|Levator Scapulae||Transverse processes of the upper 4 cervical vertebrae.||Medial border of the scapula above the base of the scapular spine.||Elevates the medial margin of the scapula.|
|Rhomboids||Spinous processes of the last cervical and the first five thoracic vertebrae.||Medial border of the scapula, below the spine.||Adduction-draws the scapula toward the spinal column; elevate slightly as they adduct.Rotation-downward from the upward rotation position; they draw the scapula in a downward rotation.|
|Serratus Anterior||Surface of the upper 9 ribs at the side of the chest.||Passes between chest wall and scapula to the whole length of the medial border of the scapula.||Protraction.Rotation upward-longer lower fibres tend to draw the inferior angle of the scapula farther away from the vertebrae, thus rotating the scapula upward slightly.|
When all the parts of the trapezius are working together, they tend to pull upward and adduct at the same time. Typical action of the trapezius muscle is flexion of the scapula for deltoid action. Continuous action in upward rotation of the scapula permits the arms to be raised overhead. The muscle is always used in preventing the glenoid fossa from being pulled down during the lifting of objects with the arms.
Shrugging of the shoulder calls the levator scapulae muscle into play along with the trapezius muscle.
The rhomboids fix the scapulae in adduction when the muscles of the shoulder joint adduct or extend the arm. These muscles are used powerfully in chinning. As one hangs from the horizontal bar, suspended by the hands, the scapula. tends to be pulled away from the top of the chest. When the chinning movement begins, it is the rhomboids that draw the medial border of the scapula down and back toward the spinal column. Chin ups and dips are an excellent exercises for developing these muscles
The serratus anterior muscle is used commonly in movements drawing the scapula forward with slight upward rotation, such as throwing. It works with the pectoralis major muscle in a typical action such as throwing.
The serratus anterior muscle is used strongly in doing push ups and especially in the last 5° to 10° of motion. The bench press and overhead press are other good exercises that help develop this muscle.
Movements of the shoulder Girdle:
Movements that occur at the sterno-clavicular (SC) and acromio-clavicular(AC) joints are always associated with movements of the scapula while movements of the scapula are ofter associated with movements of the humerus at the shoulder joint. Sternal end of the clavical is articulated in such a way as to allow lateral end of bone to be moved in all directions from an anatomical position. Greater range of movement is upwards or ELEVATION and forwards or PROTRAC ION. Smallest range of movement is downward or DEPRESSION and backward or RETRACTION.
(1) Elevation of Lateral End of Clavical – Is accompanied by some upward rotation of glenoid cavity and as lateral end is elevated the sterna end glides downwards over the articular disc.
(2) Depression – is accompanied by some downward rotation of the glenoid cavity and as lateral end of the clavicle is depressed the sterna end glides upwards on the articular disc.
(3) Forward Movement of Lateral End of Clavicle – will produce protraction of the scapulae around the chest wall and as lateral end of clavicle is carried forward the sternal end moves backward.
(4) Backward Movement of Lateral End of Clavicle – will be accompanied by retraction of scapulae and as lateral end of clavicle moves backwards the medial end glides forward over the articular disc.
(5) Upward Rotation of Glenoid Cavity – this is always accompanied by abduction of the shoulder joint. Medial end of clavicle moves downward on articular disc and at the same time is rotated downward.
(6) Downward Rotation of Glenoid Cavity – is accompanied by extension of the shoulder joint. Medial end of clavicle swings forward and upward.
Muscles Producing the Movement
Elevation 1) Upper fibres of the Trapezius
2) Levator Scapulae
Protraction 1) Serratus Anterior
Retraction 1) Middle fibres of Trapezius