Pectoral Girdle, Rotator Cuff and Upper Arm Muscles

Question 0

Pectoralis minor Origin? Insertion? Innervation? Action?

Answer 0

O: 3rd-5th ribs near their costal cartilages

I: Medial border and superior surface of coracoid process of scapula.

Innervation: Medial pectoral nerve (C8-T1)

Action: Stabilizes scapula by drawing inferiorly and anteriorly against thoracic wall.

Question 1

Pectoralis major Origin? Insertion? Innervation? Action?

Answer 1

O:
Clavicular head-> Anterior surface of medial half of clavicle
Sternocostal head-> Anterior surface of sternum, superior six costal cartilages, aponeurosis of external oblique muscle.

I: Lateral lip of intertubercular sulcus of humerus

Innervation: Lateral and medial pectoral nerves; clavicular head (C5-C6), sternocostal head (C7,C8,T1)

Action: Adducts and medially rotates humerus; draws scapula anteriorly and inferiorly. Acting alone, clavicular head flexes humerus and sternocostal head extends it from the flexed position.

Question 2

Subclavius Origin? Insertion? Innervation? Action?

Answer 2

O: Junction of 1st rib and its costal cartilage.

I: Inferior surface of middle third of clavicle.

Innervation: Subclavian nerve (C5-C6)

Action: Anchors and depresses clavicle

Question 3

Deltoid Origin? Insertion? Innervation? Action?

Answer 3

O: Lateral third of clavicle; acromion and spine of scapula

I: Deltoid tuberosity of the humerus

Innervation: Axillary nerve (C5 and C6)

Action: Clavicular (anterior) -> flexes and medially rotates arm
Acromial (middle) -> abducts arm Spinal (posterior) -> extends and laterally rotates arm

Question 4

Supraspinatus Origin? Insertion? Innervation? Action?

Answer 4

O: Supraspinous fossa of scapula

I: Superior facet of greater tubercle of humerus

Innervation: Suprascapular nerve (C4-C6)

Action: Initiates and assists deltoid in abduction of arm and acts with other rotator cuff muscles.

Question 5

Infraspinatus Origin? Insertion? Innervation? Action?

Answer 5

O: Infraspinous fossa of scapula

I: Middle facet of greater tubercle of humerus

Innervation: Suprascapular nerve (C5-C6)

Action: Laterally rotates arm; help hold humeral head in glenoid cavity of scapula.

Question 6

Teres minor Origin? Insertion? Innervation? Action?

Answer 6

O: Middle part of lateral border of scapula.

I: Inferior facet of greater tubercle of humerus

Innervation: Axillary nerve (C5-C6)

Action: Laterally rotate arm; help hold humeral head in glenoid cavity of scapula.

Question 7

Teres major Origin? Insertion? Innervation? Action?

Answer 7

O: Posterior surface of inferior angle of scapula

I: Medial lip of intertubercular groove of humerus

Innervation: Lower subscapular nerve (C5-C6)

Action: Adducts and medially rotates arm

Question 8

Subscapularis Origin? Insertion? Innervation? Action?

Answer 8

O: Subscapular fossa (most of anterior surface of scapula)

I: Lesser tubercle of humerus

Innervation: Upper and lower subscapular nerves (C5-C7)

Action: Medially rotates and adducts arm; helps hold humeral head in glenoid cavity.

Question 9

Biceps brachii Origin? Insertion? Innervation? Action?

Answer 9

O:
Short head-> Tip of coracoid process of scapula
Long head -> Supraglenoid tubercle of scapula

I: Tuberosity of radius and fascia of forearm via bicipital aponeurosis

Innervation: Musculocutaneous nerve (C5-C6)

Action: Supinates forearm and, when it is supinated, flexes forearm; flexes arm; short head resists dislocation of shoulder

Question 10

Brachialis Origin? Insertion? Innervation? Action?

Answer 10

O: Distal half of anterior surface of humerus

I: Coronoid process and tuberosity of ulna

Innervation: Musculocutaneous nerve (C5-C6)

Action: Flexes forearm in all positions

Question 11

Coracobrachialis Origin? Insertion? Innervation? Action?

Answer 11

O: Tip of coracoid process of scapula

I: Middle third of medial surface of humerus

Innervation: Musculocutaneous nerve (C5-C7)

Action: Helps flex and adduct arm; resists dislocation of shoulder

Question 12

Triceps brachii Origin? Insertion? Innervation? Action?

Answer 12

O:
Long head-> Infraglenoid tubercle of scapula
Lateral head-> Posterior surface of humerus, superior to radial groove
Medial head-> Posterior surface of humerus, inferior to radial groove

I: Proximal end of olecranon of ulna and fascia of forearm

Innervation: Radial nerve (C6-C8)

Action: Chief extensor of forearm; long head extends arm and resists dislocation of humerus (especially important during abduction)

Question 13

Anconeus Origin? Insertion? Innervation? Action?

Answer 13

O: Lateral epicondyle of humerus

I: Lateral surface of olecranon and superior part of posterior surface of ulna

Innervation: Radial nerve (C7,C8,T1)

Action: Assists triceps in extending forearm; stabilizes elbow joint; abducts ulna during pronation.

Question 14

Acromioclavicular joint is a plane synovial articulation, which maintains most of its strength from the coracoclavicular ligament (prevents the acromion from being driven under the clavicle even when the AC joint is separated). What arteries and nerves supply the AC joint?

Answer 14

Arteries: Suprascapular and thoraco-acromial arteries

Nerves: Supraclavicular, lateral pectoral and Axillary nerves

Question 15

Sternoclavicular joint is a saddle joint but functions like a ball and socket joint… What arteries and nerves supply the SC joint?

Answer 15

Arteries: Internal thoracic and suprascapular arteries

Nerves: Branches of the medial supraclavicular nerve and the subclavian nerve.

Question 16

Glenohumeral joint is a ball and socket synovial joint that had a wide range of movement, which compromises its stability. Capsule is deepened by the glenoid labrum. What arteries and nerves supply the glenohumeral joint?

Answer 16

Arteries: Anterior and posterior circumflex humeral arteries and branches of the suprascapular artery.

Nerves: Suprascapular, axillary, and lateral pectoral nerves supply the glenohumeral joint.

Question 17

What joints produces flexion of the shoulder? What structures limit this movement?

Answer 17

Sternoclavicular, acromioclavicular, glenohumeral, and scapulothoracic joints permit flexion.

Limiting ligaments: Posterior part of coracohumeral, trapezoid, and posterior part of joint capsule of glenohumeral joint.

Limiting muscles: Rhomboids, levator scapulae, extensor and external rotator muscles, rotator muscles of glenohumeral joint.

Question 18

What joints produces abduction of the shoulder? What structures limit this movement?

Answer 18

Sternoclavicular, acromioclavicular, glenohumeral, and scapulothoracic joints.

Limiting ligaments: Middle and inferior glenohumeral, trapezoid, and inferior parts of joint capsule of glenohumeral joint.

Limiting muscles: Rhomboids, levator scapulae, adductor muscles of glenohumeral joint

Bony apposition: Between greater tubercle of humerus and superior part of glenoid cavity/labrum or lateral aspect of acromion.

Question 19

What joints produces extension of the shoulder? What structures limit this movement?

Answer 19

The glenohumeral joint.

Limiting ligaments: Anterior part of coracohumeral and anterior part of joint capsule of glenohumeral joint.

Limiting muscles: Clavicular head of pectoralis major.

Question 20

What joints produces internal rotation of the shoulder? What structures limit this movement?

Answer 20

The glenohumeral joint.

Limiting ligaments: Posterior glenohumeral joint capsule

Limiting muscles: Infraspinatus and teres minor

Question 21

What joints produces external rotation of the shoulder? What structures limit this movement?

Answer 21

The glenohumeral joint.

Limiting ligaments: Glenohumeral, coracohumeral, anterior glenohumeral joint capsule.

Limiting muscles: Latissimus dorsi, teres major, pectoralis major, and subscapularis.

Question 22

Serratus anterior Origin? Insertion? Innervation? Action?

Answer 22

O: External surfaces of lateral parts of 1st-8th ribs

I: Anterior surface of medial border of scapula

Innervation: Long thoracic nerve(C5-C7)

Action: Protracts scapula and holds against thoracic wall; rotates scapula