Shoulder region: Muscles

List 5 muscles that may act to stabilise (or depress) the pectoral girdle for weight bearing purposes such as using crutches or lifting yourself off a chair.

1. Latissimus dorsi 2. Pectoralis major 3. Pectoralis minor 4. Subclavius 5. Lower trapezius

Trapezius - upper:

Action: Clavicular elevation, scapular elevation, add, upward rotation. Distal attachment: Lateral clavicle I: Motor spinal part of accessory nerve CN XI

Latissimus dorsi:

Action: Extension, adduction, medial rotation. Distal attachment: T7-T12, Lumbar & sacral spinous processes, posterior iliac crest, and lower 3 ribs. Proximal attachment: Intertubercular sulcus & inferior angle of scapular. I: Thoracodorsal nerve C6-C8.

Pectoralis major - Sternocostal head:

Action: Extension, medial rotation, horizontal flexion Proximal attachment: Sternum and 1st-7th costal cartilages Distal attachment: Lateral lip of intertubercular sulcus. I: Medial and lateral pectoral nerves C8-T1

Pectoralis major - Clavicular head:

Action: Flexion, medial rotation, horizontal flexion Proximal attachment: medial 2/3 clavicle Distal attachment: Lateral lip of interbercular sulcus of humerus. I: Medial and lateral pectoral nerves C8-T1.

Sternocleidomastoid:

Action: Moves head and neck Proximal attachment: Manubrium and medial clavicle Distal attachment: Mastoid process and lateral superior nuchal line. I: Motor spinal part of accessory nerve CN XI

Subclavius:

Action: Pulls clavicle medially to stabilise SCJ. Proximal attachment: 1st Rib Distal attachment: Inferior medial 1/3 clavicle I: Nerve to subclavius (C5-C6)

Pectoralis minor:

Action: Scapular anterior tilt Proximal attachment: Anterior ribs 3-5 Distal attachment: Coracoid process I: Medial and lateral pectoral nerves C8-T1

Trapezius - lower:

Action: Scapular depression & upward rotation Proximal attachment: igamentum nuchae & C7-T12 spinous processes. Distal attachments: Medial spine of scapular. I: Motor spinal part of accessory nerve CN XI

Rhomboid major:

Action: Scapular elevation, adduction, and downward rotation. Proximal attachment: T2-T5 spinous processes. Distal attachment: medial border of scapular, below medial spine of scapular. I: Dorsal scapular nerve C5

Levator Scapulae:

Action: Scapular elevation, adduction, and downward rotation. Distal attachment: Medial border scapular above medical spine of scapular. I: C3,C4 Ventral rami and Dorsal Scapular nerve C5.

Rhomboid minor:

Action: Scapular elevation, adduction, and downward rotation. Proximal attachment: Ligamentum nuchae, C7 & T1. Distal attachment: Medial border of scapular medial spine of scapular. I: Dorsal scapular nerve C5

Serratus anterior:

Action: Scapular protraction/abd, and upward rotation. Distal attachment: Medial, ventral border of scapular. I: Long thoracic nerve C5,6,7

Trapezius - middle:

Action: Scapular retraction/add Proximal attachment: Ligamentum nuchae & C7-T12 spinous processes. Distal attachment: Acromion process and spine of scapular. I: Motor spinal part of accessory nerve CN XI

Name the muscles responsible for flexion at GHJ.

Anterior deltoid, Middle deltoid, Clavicular head of pectoralis major, coracobrachialis, and biceps brachii.

Describe the force couple between pectorals minor and lower trapezius.

Both muscles work together to depress the scapular. Pectoralis minor does downwards rotation whereas lower trapezius does upward rotation of scapular.

Which passive and active structures provide support to the GHJ in anatomical position?

Deltoid muscle, rotator cuff group (infraspinatus, supraspinatus, subscapularis, teres minor).

What is the primary muscle producing abduction at the GHJ? Explain why

Deltoid up to 90 degrees, larger muscle, large PCSA and therefore larger opportunity to generate force.

What is the function of serratus anterior during weight bearing through the upper limb?

Holds medial border of scapular in place, on the thoracic cage.

What muscles are responsible for downward rotation of scapular?

Levator scapulae, rhomboid major, rhomboid minor, pectoralis minor.

Which muscles is responsible for scapular depression?

Lower trapezius and pectoralis minor.

What is scapular medial winging?

Medial aspect of scapular lifts during activities which require shoulder elevation.

Name muscles responsible for abduction at GHJ.

Middle deltoid, Anterior deltoid, and Supraspinatus (SST).

What is the cause of medial winging of scapular?

Muscle weakness: Weakness in serratus anterior muscle. OR Nerve dysfunction: Can be caused by serratus anterior palsy where traumatic, non-traumatic or idiopathic injury to the long thoracic nerve (C5,C6,C7).

Draw/imagine scapular and indicate the muscles which produce downward rotation of scapula. Indicate line of action of each muscle with arrow.

Muscles responsible: Levator scapulae, rhomboid major, and rhomboid minor.

Draw/imagine scapular and indicate the muscles which produce upward rotation of scapula. Indicate line of action of each muscle with arrow.

Muscles responsible: Upper, middle and lower trapezius and serratus anterior.

Name muscles responsible for Horizontal adduction.

Pectoralis major, and Anterior deltoid.

What muscle/s are responsible for scapular anterior tilt?

Pectoralis minor.

Name muscles responsible for horizontal abduction.

Posterior deltoid, and infraspinatus.

What structures control movement of the humeral head on the glenoid through the normal ranges of active movements?

Rotator cuff stops excessive superior translation of humeral head.

Which muscles are responsible for scapular abduction/protraction?

Serratus anterior (pictured) and pectoralis minor.

Describe force couple between serratus anterior and rhomboid major/minor?

Serratus anterior has the role of protracting or downward rotation of scapular, whereas rhomboid major and minor have the role of retraction of scapular. Therefore the retraction and protraction both cancel each other out.

Explain the function of serratus anterior when holding a weight overhead?

Stabilises scapular and upward rotation. Also, keeps scapular on thorax during abduction.

Name muscles responsible for extension at GHJ.

Sternal head of pectoralis major, Latissimus dorsi, Teres major, and Posterior deltoid.

Which muscle is responsible for Clavicular depression?

Subclavius.

Name muscles responsible for Internal rotation at GHJ.

Supraspinatus, Pectoralis major - clavicular portion, Subscapularis, Teres major, Latissimus dorsi.

Name muscles responsible for external rotation at GHJ.

Supraspinatus, infraspinatus, and teres minor.

Name muscles responsible for adduction at GHJ.

Teres minor, lattissimus dorsi, subscapularis, and teres major.

Draw/describe force couple between deltoid and the rotator cuff during GHJ abduction.

The three of the rotator cuff muscles teres minor, subscapularis and infraspinatus have a inferior line of action whereas the deltoid has a superior line of action whilst performing abduction. This relationship acts to exert greater compression which reduces the amount of translation between the HOH and glenoid fossa. This reduces the chance of impingement of the items in the subacromial space (tendons/bursa etc).

Which muscles are responsible for Scapualr elevation?

Upper trapezius, Levator Scapulae, Rhomboid minor, Rhomboid major.

Which muscles are responsible for scapular adduction/retraction?

Upper trapezius, middle trapezius, lower trapezius, Rhomboid major, Rhomboid minor, Levator scapulae.

What muscles are responsible for upward rotation of scapular? (Inferior border of scapula moves outwards/up).

Upper trapezius, middle trapezius, lower trapezius, serratus anterior.

What muscle is responsible for sternoclavicular/clavicle elevation?

Upper trapezius.