UE Muscle Actions, Origins and Insertions

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Questions and Answers

What is the origin of the Subscapularis muscle?

Nuchal ligament & spinous processes of CV7 & TV1

Dorsal surface of inferior angle of scapula

Spinous processes TV2-TV5

Subscapular fossa (correct)

Where does the Teres Major muscle insert?

Radial tuberosity

Medial border of scapula

Floor of intertubercular groove of humerus

Medial lip of intertubercular groove of humerus (correct)

Which muscle is responsible for internal rotation and adduction of the humerus?

Subscapularis (correct)

Latissimus dorsi

Rhomboids Major

Biceps brachii

The Rhomboid Major muscle acts to elevate and retract the scapula. What is its origin?

Spinous processes TV2-TV5 Signup and view all the answers

Which muscle originates from the thoracolumbar fascia and the inferior 3 or 4 ribs?

Latissimus dorsi Signup and view all the answers

What is the primary action of the Coracobrachialis muscle?

Flexion with adduction Signup and view all the answers

Which nerve innervates the Biceps Brachii muscle?

Musculocutaneous nerve Signup and view all the answers

What muscle is primarily involved in stabilizing the humeral head in the glenoid?

Subscapularis Signup and view all the answers

What is the origin of the pectoralis minor muscle?

3rd to 5th ribs near costal cartilages Signup and view all the answers

Which muscle is responsible for initiating and assisting the deltoid in abduction of the humerus?

Supraspinatus Signup and view all the answers

What is the insertion point for the anterior deltoid muscle?

Deltoid tuberosity of the humerus Signup and view all the answers

What action does the posterior deltoid perform?

Externally rotates the humerus Signup and view all the answers

What is the primary function of the infraspinatus muscle?

External rotation of the humerus Signup and view all the answers

Which structure stabilizes the humeral head in the glenoid cavity?

Supraspinatus Signup and view all the answers

Which of the following muscles innervates the teres minor?

Axillary nerve Signup and view all the answers

What is the main action of the pectoralis major muscle?

Adducts and medially rotates the humerus Signup and view all the answers

What is the origin of the Brachialis muscle?

Distal half of the humerus, anterior surface Signup and view all the answers

Which muscle is responsible for elbow flexion regardless of position?

Brachialis Signup and view all the answers

What is the insertion point for the Triceps muscle?

Olecranon process of the ulna Signup and view all the answers

Which muscle acts to supinate the forearm?

Biceps brachii Signup and view all the answers

The origin of the Pronator teres includes which of the following?

Medial epicondyle of the humerus Signup and view all the answers

What is the primary action of the Brachioradialis muscle?

Elbow flexion in midpronation Signup and view all the answers

Where does the Supinator muscle primarily insert?

Proximal radius, anterior and lateral surface Signup and view all the answers

Which nerve innervates the Triceps muscle?

Radial n. Signup and view all the answers

Study Notes

Muscles of the Upper Extremity

Subscapularis:
- Rotator cuff muscle
- Located on the subscapular fossa of the scapula
- Inserts on the lesser tubercle of the humerus
- Innervated by the upper and lower subscapular nerves (C5, C6)
- Actions: Internally rotates and adducts the humerus, helps hold the humeral head in the glenoid fossa
Teres Major:
- Located on the dorsal surface of the inferior angle of the scapula
- Inserts on the medial lip of the intertubercular groove of the humerus
- Innervated by the lower subscapular nerve (C5, C6)
- Actions: Extends, adducts, and internally rotates the humerus
Rhomboid Major:
- Located on the spinous processes of T2-T5
- Inserts on the medial border of the scapula from the spine to the inferior angle
- Innervated by the dorsal scapular nerve (C4-C5)
- Actions: Retracts, elevates, and downwardly rotates the scapula; fixes the scapula against the thoracic wall
Rhomboid Minor:
- Located on the nuchal ligament and spinous processes of C7 and T1
- Inserts on the medial border of the scapula at the level of the spine
- Innervated by the dorsal scapular nerve (C4-C5)
- Actions: Retracts, elevates, and downwardly rotates the scapula; fixes the scapula against the thoracic wall
Latissimus Dorsi:
- Located on the thoracolumbar fascia, spinous processes of T6 to T12, inferior 3 or 4 ribs, and iliac crest
- Inserts on the floor of the intertubercular groove of the humerus
- Innervated by the thoracodorsal nerve (C6, C7, C8)
- Actions: Extends, adducts, and internally rotates the humerus
Coracobrachialis:
- Located on the tip or apex of the coracoid process of the scapula
- Inserts on the middle 1/3, medial humerus
- Innervated by the musculocutaneous nerve (C5, C6, C7)
- Actions: Flexes and adducts the humerus
Biceps Brachii:
- Has two heads:
  - Short head: originates from the coracoid process of the scapula
  - Long head: originates from the supraglenoid tubercle of the scapula
- Inserts on the radial tuberosity and fascia of the forearm
- Innervated by the musculocutaneous nerve (C5-C6)
- Actions:
  - Short head: Flexes the humerus
  - Long head: Flexes the elbow and supinates the forearm; steadies the head of an abducted humerus
  - Clavicular head (alone): Flexes the humerus
Pectoralis Major:
- Has two heads:
  - Sternocostal head: originates from the anterior surface of the sternum, upper 6 costal cartilages, and aponeurosis of the external oblique muscle
  - Clavicular head: originates from the medial 1/3 of the clavicle
- Inserts on the lateral lip of the intertubercular groove of the humerus
- Innervated by:
  - Sternocostal head: C7, C8-T1
  - Clavicular head: C5-C6
- Actions:
  - Sternocostal head: Extends the humerus from an overhead position; horizontally adducts the humerus at the glenohumeral joint
  - Clavicular head: Flexes the humerus
Pectoralis Minor:
- Located on the 3rd to 5th ribs near the costal cartilages
- Inserts on the medial border and superior surface of the coracoid process of the scapula
- Innervated by the medial and lateral pectoral nerves (C6, C7, C8)
- Actions: Stabilizes the scapula by drawing it inferiorly and anteriorly against the thoracic wall
Anterior Deltoid:
- Located on the lateral 1/3 of the clavicle, anterior surface
- Inserts on the deltoid tuberosity of the humerus
- Innervated by the axillary nerve (C5, C6)
- Actions: Abducts, flexes, and internally rotates the humerus
Middle Deltoid:
- Located on the lateral aspect of the acromion
- Inserts on the deltoid tuberosity
- Innervated by the axillary nerve (C5, C6)
- Actions: Abducts the humerus
Posterior Deltoid:
- Located on the inferior lip of the crest of the spine of the scapula
- Inserts on the deltoid tuberosity
- Innervated by the axillary nerve (C5, C6)
- Actions: Extends, externally rotates, and abducts the humerus
Supraspinatus:
- Located in the supraspinous fossa (medial 2/3) of the scapula
- Inserts on the superior facet on the greater tubercle of the humerus
- Innervated by the suprascapular nerve (C4, C5, C6)
- Actions: Initiates and assists the deltoid in abduction of the humerus; holds the head of the humerus in the glenoid cavity (rotator cuff)
Infraspinatus:
- Located in the infraspinous fossa of the scapula
- Inserts on the middle facet of the greater tubercle of the humerus
- Innervated by the suprascapular nerve (C5, C6)
- Actions: Externally rotates the humerus; helps hold the humeral head in the glenoid cavity (rotator cuff)
Teres Minor:
- Located on the middle part of the lateral border of the scapula
- Inserts on the inferior facet on the greater tubercle of the humerus
- Innervated by the axillary nerve (C5-C6) via the bicipital aponeurosis
- Actions: Externally rotates the humerus; helps hold the humeral head in the glenoid cavity (rotator cuff); weak abduction if the humerus is externally rotated
Brachialis:
- Located on the distal half of the humerus, anterior surface
- Inserts on the ulnar tuberosity and anterior aspect of the coronoid process of the ulna
- Innervated by the musculocutaneous nerve (C5-C6)
- Actions: Flexes the elbow regardless of forearm position
Brachioradialis:
- Located on the proximal 2/3 of the lateral supracondylar ridge of the humerus
- Inserts on the lateral surface of the distal end of the radius
- Innervated by the radial nerve (C5, C6, C7)
- Actions: Flexes the elbow (most effective in mid pronation)
Triceps Brachii:
- Has three heads:
  - Long head: originates from the infraglenoid tubercle of the scapula
  - Lateral head: originates from the posterior surface of the humerus, superior to the radial groove
  - Medial head: originates from the posterior surface of the humerus, inferior to the radial groove
- Inserts on the proximal end of the olecranon process of the ulna and fascia of the forearm
- Innervated by the radial nerve (C6, C7, C8)
- Actions: Extends the elbow; long head steadies the head of an abducted humerus
Pronator Teres:
- Has two heads:
  - Humeral head: originates from the medial epicondyle of the humerus
  - Ulnar head: originates from the coronoid process of the ulna
- Inserts on the middle of the lateral surface of the radius
- Innervated by the median nerve (C6-C7)
- Actions: Pronates the forearm; flexes the elbow
Pronator Quadratus:
- Located on the distal 1/4 of the anterior surface of the ulna
- Inserts on the distal 1/4 anterior surface of the radius
- Innervated by the anterior interosseous nerve (from the median nerve) (C8-T1)
- Actions: Pronates the forearm
Supinator:
- Located on the lateral epicondyle of the humerus, and the radial collateral ligament
- Inserts on the proximal radius, anterior, lateral, and posterior surfaces
- Innervated by the deep branch of the radial nerve
- Actions: Supinates the forearm