6. Muscles of the Shoulder Girdle and Arm



Muscles of the Shoulder Girdle and Arm


The muscles of this chapter are involved with the motions of the shoulder girdle (scapula and clavicle), arm (humerus), and forearm (radius and ulna). The bellies of these muscles are located on the trunk, over the scapula, and on the arm. Trapezius, latissimus dorsi, and pectoralis major are large superficial muscles located on the trunk. Deltoid, triceps brachii, and biceps brachii (and to some degree the brachialis) are large superficial muscles located on the scapula and arm.


As a general rule, muscles that move the shoulder girdle have their origin (proximal attachment) on the trunk and their insertion (distal attachment) on the scapula or clavicle or both. These muscles move the scapula relative to the rib cage wall (trunk) at the scapulocostal joint and/or the clavicle at the sternoclavicular joint.


Muscles that move the arm have their origin (proximal attachment) on the trunk, clavicle, or scapula and their insertion (distal attachment) on the humerus. These muscles move the arm relative to the scapula at the glenohumeral joint.


Muscles that move the forearm have their origin (proximal attachment) on the scapula or humerus and their insertion (distal attachment) on the radius or ulna.


The companion CD at the back of this book allows you to examine the muscles of this body region, layer by layer, and individual muscle palpation technique videos are available in the Chapter 6 folder on the Evolve website.


OVERVIEW OF FUNCTION: MUSCLES OF THE SHOULDER GIRDLE


The following general rules regarding actions can be stated for the functional groups of muscles of the shoulder girdle:



ent If a muscle attaches to the scapula and its other attachment is superior to the scapula, it can elevate the scapula at the scapulocostal joint.


ent If a muscle attaches to the scapula and its other attachment is inferior to the scapula, it can depress the scapula at the scapulocostal joint.


ent If a muscle attaches to the scapula and its other attachment is medial to the scapula on the posterior side (i.e., closer to the spine), it can retract (adduct) the scapula at the scapulocostal joint.


ent  If a muscle attaches to the scapula and its other attachment is lateral to the scapula (i.e., closer to the anterior surface of the body), it can protract (abduct) the scapula at the scapulocostal joint. If a muscle attaches to the scapula away from the axis of scapular rotation (i.e., off axis), it can rotate the scapula either upwardly or downwardly at the scapulocostal joint. The rotation that the scapula performs depends on where it attaches.


ent Any muscle that moves the scapula at the scapulocostal joint can do the same motion of the clavicle at the sternoclavicular joint (and vice versa).


ent Reverse actions of these standard (typical) mover actions involve the scapula being fixed and the other attachment moving toward the scapula at the scapulocostal joint.*


OVERVIEW OF FUNCTION: MUSCLES OF THE GLENOHUMERAL JOINT


The following general rules regarding actions can be stated for the functional groups of muscles of the glenohumeral joint:



ent If a muscle crosses the glenohumeral joint anteriorly with a vertical direction to its fibers, it can flex the arm at the glenohumeral joint by moving the anterior surface of the arm toward the scapula.


ent If a muscle crosses the glenohumeral joint posteriorly with a vertical direction to its fibers, it can extend the arm at the glenohumeral joint by moving the posterior surface of the arm toward the scapula.


ent If a muscle crosses the glenohumeral joint laterally (superiorly, over the top of the joint), it can abduct the arm at the glenohumeral joint by moving the lateral surface of the arm toward the scapula.


ent If a muscle crosses the glenohumeral joint medially (inferiorly, below the center of the joint), it can adduct the arm at the glenohumeral joint by moving the medial surface of the arm toward the scapula.


ent Medial rotators of the arm wrap around the humerus from medial to lateral, anterior to the glenohumeral joint.


ent Lateral rotators of the arm wrap around the humerus from medial to lateral, posterior to the glenohumeral joint.


ent Reverse actions of these standard (typical) mover actions involve the scapula being moved relative to the humerus at the glenohumeral joint (the scapula will also be moved relative to the rib cage at the scapulocostal joint). These reverse actions are usually either rotation or tilt actions of the scapula.*


OVERVIEW OF FUNCTION: MUSCLES OF THE ELBOW AND RADIOULNAR JOINTS


The following general rules regarding actions can be stated for the functional groups of muscles of the elbow and radioulnar joints:



ent If a muscle crosses the elbow joint anteriorly with a vertical direction to its fibers, it can flex the forearm at the elbow joint by moving the anterior surface of the forearm toward the anterior surface of the arm.


ent If a muscle crosses the elbow joint posteriorly with a vertical direction to its fibers, it can extend the forearm at the elbow joint by moving the posterior surface of the forearm toward the posterior surface of the arm.


ent Reverse actions at the elbow joint involve moving the arm toward the forearm at the elbow joint. This movement usually occurs when the hand (and therefore the forearm) is fixed by holding onto an immovable object.*


ent If a muscle crosses the radioulnar joints anteriorly with a horizontal orientation to its fibers, it will pronate the forearm at the radioulnar joints by crossing the radius over the ulna.


ent If a muscle crosses the radioulnar joints posteriorly with a horizontal direction to its fibers, it will supinate the forearm at the radioulnar joints by moving the radius to be parallel with the ulna.


ent Reverse actions of these standard (typical) mover actions at the radioulnar joints involve moving the ulna toward the radius at the radioulnar joints. This movement usually occurs when the hand (and therefore the radius) is fixed by holding onto an immovable object.*




image
FIGURE 6-3


ATTACHMENTS


Origin (Proximal/Medial Attachment)



Insertion (Distal/Lateral Attachment)



ACTIONS


The trapezius moves the scapula at the scapulocostal joint and moves the head and neck at the spinal joints.


Upper Fibers


Middle Fibers


Lower Fibers



INNERVATION



PALPATION



1. Ask the client to lie prone with the arm resting on the table at the side of the body.


2. To palpate the lower and middle trapezius, place the palpating finger pads just lateral to the lower and middle thoracic spine. Then ask the client to abduct the arm to 90 degrees with the elbow joint extended; and slightly retract the scapula by pinching the shoulder blade toward the spine. Adding gentle resistance to the client’s arm abduction with your support hand is usually helpful. Palpate perpendicular to the fibers between the spine and scapula (Figure 6-5, A).


3. To palpate the upper trapezius, ask the client to extend the head slightly. Look for the engagement of the upper trapezius and palpate it in the neck up to its occipital attachment (Figure 6-5, B).


4. Note that the upper trapezius is quite narrow; it only attaches to the medial one third of the superior nuchal line of the occiput. The semispinalis capitis muscle, the largest muscle in the neck, is deep to the upper trapezius.



TREATMENT CONSIDERATIONS



image


ATTACHMENTS


Origin (Proximal/Medial Attachment)



Insertion (Distal/Lateral Attachment)




INNERVATION



PALPATION




TREATMENT CONSIDERATIONS




ATTACHMENTS


Origin (Proximal/Superior Attachment)



Insertion (Distal/Inferior Attachment)



ACTIONS


The levator scapulae moves the scapula at the scapulocostal joint and moves the neck at the spinal joints.



STABILIZATION



PALPATION





Note: The transverse process of C1 is immediately inferior to the ear.


TREATMENT CONSIDERATIONS




ATTACHMENTS


Origin (Proximal/Anterior Attachment)



Insertion (Distal/Posterior Attachment)




INNERVATION



PALPATION




TREATMENT CONSIDERATIONS




ATTACHMENTS


Pectoralis Major


Origin (Proximal/Medial Attachment)



Insertion (Distal/Lateral Attachment)



Pectoralis Minor


Origin (Proximal/Anterior Attachment)



Insertion (Distal/Posterior Attachment)


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Aug 22, 2016 | Posted by in MUSCULOSKELETAL MEDICINE | Comments Off on 6. Muscles of the Shoulder Girdle and Arm

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