The Shoulder

The two bones of the shoulder girdle articulate with each other at what joint?

Acromioclavicular joint

The suspensory ligament of the axilla attaches to what other fascia?

Axillary fascia on the base of the axilla

What is the most commonly fractured bone in the body?

Clavicle

What does the shoulder girdle consist of?

Clavicle and the scapula

T/F: The teres major muscle is a rotator cuff muscle.

False. Rotator cuff muscles are: supraspinatus, infraspinatus, teres minor, and subscapularis.

Patients with ruptured supraspinatus tendons are unable to do what?

INITIATE abduction of the arm (however, if you lift their arm, initiating the motion, their deltoid muscle can then abduct)

What direction is the head of the humerus commonly dislocated toward? Why? What nerve could be injured during such a dislocation?

Inferiorly, because the inferior aspect of the joint is weak; the axillary nerve runs under the joint and can thus be injured if the humerus is dislocated inferiorly

Innervation and action of subscapularis muscle?

Innervation: Upper and lower subscapular nerves (fibers from C5 and C6 ventral rami; branches of posterior cord of brachial plexus) Action: helps stabilize shoulder joint; medial rotator of the arm at the shoulder joint

Innervation and action of the deltoid muscle?

Innervation: axillary nerve (fibers from C5 and C6 ventral rami, terminal branch of posterior cord of brachial plexus) Action: abduction at the shoulder joint; anterior fibers flex and medially rotate the arm; posterior fibers extend and laterally rotate the arm

Innervation and action of teres minor muscle?

Innervation: axillary nerve (fibers from C5 and C6 ventral rami, terminal branch of posterior cord of brachial plexus) Action: helps stabilize the shoulder joint; laterally rotates the arm at the shoulder joint

Innervation and action of serratus anterior muscle?

Innervation: long thoracic nerve (fibers from C5-C7 ventral rami of roots of brachial plexus) Action: holds the scapula against the thoracic wall and rotates the scapula (allows you to raise your arm above your head)

Innervation and action of teres major muscle?

Innervation: lower subscapular nerve (fibers from C5 and C6 ventral rami; branch of posterior cord of brachial plexus) Action: medial rotation, extension, and adduction of the arm at the shoulder joint

Innervation and action of pectoralis minor muscle?

Innervation: medial pectoral nerve (fibers from C8 and T1 ventral rami, branch of medial cord of brachial plexus) Action: stabilizes the scapula by drawing it against the thoracic cage inferiorly and anteriorly; also assists in forced inspiration

Innervation and action of pectoralis major muscle?

Innervation: medial pectoral nerve (fibers from C8 and T1 ventral rami, branch of medial cord of brachial plexus) and lateral pectoral nerve (fibers from C6 and C7 ventral rami, branch of lateral cord of brachial plexus) Action: flexion, adduction, and medial rotation of the arm at the shoulder joint; also assists in forced inspiration

Innervation and action of subclavius muscle?

Innervation: nerve to subclavius (fibers from C5 and C6 ventral rami of roots of brachial plexus) Action: depresses the clavicle and braces the clavicle against the sternum

Innervation and action of supraspinatus muscle?

Innervation: suprascapular nerve (fibers from C5 and C6 ventral rami, branch of upper trunk of brachial plexus) Action: helps stabilize shoulder joint (holds head of humerus in glenoid fossa); initiates and assists the deltoid in abduction of the arm at the shoulder joint

Innervation and action of infraspinatus muscle?

Innervation: suprascapular nerve (fibers from C5 and C6 ventral rami, branch of upper trunk of brachial plexus) Action: helps stabilize the shoulder joint; laterally rotates the arm at the shoulder joint

Name the rotator cuff muscles.

Mnemonic: SITS Supraspinatus (superior) Infraspinatus (posterior) Teres minor (posterior) Subscapularis (anterior)

What are the branches of the axillary nerve?

Muscular branches to deltoid and teres minor muscles; articular branch to the shoulder joint; upper lateral cutaneous nerve of arm (superior lateral brachial cutaneous nerve)

Origin and insertion of subclavius muscle?

Origin: 1st rib and 1st costal cartilage Insertion: inferior surface of middle third of clavicle

Origin and insertion of pectoralis major muscle?

Origin: Clavicular head - medial half of clavicle; Sternocostal head - sternum, upper 6 costal cartilages and aponeurosis of external oblique muscle Insertion: Lateral lip of bicipital (intertubercular) groove of humerus

Origin and insertion of serratus anterior muscle?

Origin: external surface of 1st through 8th ribs Insertion: medial border and inferior angle of scapula

Origin and insertion of infraspinatus muscle?

Origin: infraspinous fossa of scapula Insertion: greater tubercle of the humerus (middle facet)

Origin and insertion of deltoid muscle?

Origin: lateral third of clavicle, acromion, and spine of the scapula Insertion: deltoid tuberosity on the shaft of the humerus

Origin and insertion of teres major muscle?

Origin: lower part of the lateral border of the scapula and posterior aspect of inferior angle of scapula Insertion: medial lip of the bicipital (intertubercular) groove of humerus

Origin and insertion of teres minor muscle?

Origin: middle part of the lateral border of the scapula Insertion: greater tubercle of the humerus (lower facet)

Origin and insertion of pectoralis minor muscle?

Origin: ribs 3, 4, and 5 Insertion: coracoid process of scapula

Origin and insertion of subscapularis muscle?

Origin: subscapular fossa (anterior aspect of scapula) Insertion: lesser tubercle of humerus

Origin and insertion of supraspinatus muscle?

Origin: supraspinous fossa of the scapula Insertion: greater tubercle of the humerus (upper facet)

What is a winged scapula? What is a possible cause?

Paralysis of the serratus anterior muscle causes the medial border of the scapula to protrude posteriorly; caused by injured long thoracic nerve, possibly during a mastectomy

What are the anterior axioappendicular muscles?

Pectoralis major, pectoralis minor, serratus anterior, subclavius

What is the most commonly dislocated large joint?

Shoulder joint (glenohumeral joint)

From the posterior view, what are the superior, inferior, medial and lateral boundaries of the quadrangular space?

Superior - teres minor muscle Inferior - teres major muscle Medial - long head of triceps brachii muscle Lateral - surgical neck of humerus

Degenerative changes in the subacromial bursa can lead to degenerative changes in what? What is this medical condition called?

Supraspinatus tendon; supraspinatus tendinitis

What are the posterior axioappendicular muscles?

Trapezius, latissimus dorsi, levator scapulae, rhomboid minor and major

Where is the triangular space located, in relation to the quadrangular space?

Triangular space is medial to quadrangular space

T/F: The stability of the shoulder joint has been sacrificed for a wider range of motion.

True

The quadrangular space allows for communication between the ____ and the ____.

axilla and the posterior aspect of the shoulder region

What structures pass through the quadrangular space?

axillary nerve and posterior circumflex humeral vessels

What structures pass through the triangular space?

circumflex scapular vessels

The clavipectoral fascia is called ____ between the subclavius and pectoralis minor muscles, but is called ____ inferior to the pectoralis minor muscle.

costocoracoid membrane; the suspensory ligament of the axilla

Name the scapulohumeral muscles.

deltoid, supraspinatus, infraspinatus, teres minor, teres major, and subscapularis muscles

Scapulohumeral muscles are also called _____.

intrinsic muscles of the shoulder

The clavipectoral fascia is located deep to the _____.

pectoralis major muscle

The axillary nerve originates from what part of the brachial plexus? Where do its fibers originate?

posterior cord; ventral rami of C5 and C6 spinal nerves

What two muscles are enclosed by the clavipectoral fascia?

subclavius and pectoralis minor muscles

What is the superior boundary of the quadrangular space when viewed anteriorly?

subscapularis muscle

When viewed anteriorly from the axilla, what is the superior boundary of the triangular space?

subscapularis muscle