Upper limb muscles

Question 1

What is the origin and root value of the musculocutaneous nerve?

Answer 1

• C5-C7 from the lateral cord

Question 2

What is the origin and root value of the median nerve?

Answer 2

• C6-T1 from that lateral and medial cords

Question 3

What is the origin and root value of the ulnar nerve?

Answer 3

• C8-T1 from the medial cord

Question 4

What is the origin and root value of the axillary nerve?

Answer 4

• C5-C6 from posterior cord

Question 5

What is the origin and root value of the radial nerve?

Answer 5

• C5-T1 from posterior cord

Question 6

What is the origin and root value of the long thoracic nerve?

Answer 6

• C5-7 directly from anterior rami of spinal nerves i.e. from the roots

Question 7

What is the origin and root value of the medial pectoral nerve?

Answer 7

• C8-T1 from medial cord

Question 8

What is the origin and root value of the lateral pectoral nerve?

Answer 8

• C5-C7 from lateral cord

Question 9

Pectoralis major (origins)

Answer 9

• Clavicular head originates from anterior surface of medial clavicle
• Sternocostal head originates from anterior surface of
  sternum, upper six costal cartilages and the aponeurosis of the external oblique muscle

Question 10

Pectoralis major (minus origins)

Answer 10

• Insertion = intertubercular sulcus of the humerus
• Action = Adducts arm, flexes arm at shoulder joint, internally rotates shoulder
• Innervation = medial pectoral nerve (C8-T1) and lateral pectoral nerve (C5-7)

Question 11

Pectoralis minor

Answer 11

• Originates from 3rd-5th ribs
• Inserts into coracoid process of the scapula
• Action = stabilises scapula
• Innervation = medial pectoral nerve (C8-T1)

Question 12

Serratus anterior

Answer 12

• Originates from lateral aspects of ribs 1-8
• Insert into medial border of scapula
• Action = protracts scapula, allows upper limb to be abducted above 90 degrees at the shoulder, holds medial border of scapula against ribcage
• Innervation = long thoracic nerve (C5-C7)

Question 13

Coracobrachialis

Answer 13

• Originates from coracoid process of scapula
• Inserts onto medial surface of humeral shaft at same level of deltoid tubercle
• Action = flexes arm at shoulder and weakly adducts arm
• Innervation - musculocutaneous nerve

Question 14

Deltoid

Answer 14

• Originates from lateral third of the clavicle, acromion and spine of scapula
• Inserts onto deltoid tuberosity of humerus
• Actions = flexes and medially rotates arm at shoulder (anterior fibres), abducts arm from 15-90 degrees (middle fibres), and extends and laterally rotates arm at shoulder (posterior fibres)
• Innervation = axillary nerve

Question 15

What are the borders of the axilla?

Answer 15

• Anterior border = pectoralis major and minor
• Medial border = serratus anterior and thoracic wall
• Posterior border = scapularis, teres major, latissimus dorsi
• Lateral border = intertubercular sulcus
• Apex = lateral border of first rib
• Base = axillary fascia

Question 16

What are the extrinsic muscles of the shoulder?

Answer 16

• Superficial: trapezius and latissimus dorsi
• Deep: levator scapulae, rhomboid major, rhomboid minor

Question 17

What are the origins of the trapezius?

Answer 17

• External occipital protuberance
• Nuchal ligament
• Spinous processes of C7-T12

Question 18

What are the insertions of the trapezius?

Answer 18

• Clavicle
• Acromion
• Spine of the scapula

Question 19

What is the innervation of the trapezius?

Answer 19

• Spinal accessory nerve

Question 20

What is the action of the trapezius?

Answer 20

• Elevate the scapula and rotate it during abduction of the arm above 90 degrees
• Retract scapular and pull it innferiorly

Question 21

What is the origin of the latissimus dorsi?

Answer 21

• Spinous processes of T6-T12
• Iliac crest
• Thoracolumbar fascia
• Inferior 3 ribs

Question 22

Latissimus dorsi (minus origin)

Answer 22

• Inserts onto intertubercular sulcus of humerus
• Action = extends, adducts, and medially rotates upper limb
• Innervated by thoracodorsal nerve

Question 23

Levator scapulae

Answer 23

• Originates from transverse processes of C1-C4 vertebrae
• Inserts on medial border of scapula
• Action = elevates scapula
• Innervation = Dorsal scapula nerve

Question 24

Rhomboid minor

Answer 24

• Originates from spinous processes of the C7-T1 vertebrae
• Inserts onto medial border of scapula
• Action = retracts scapula and rotates medial border, helps return arm to original position after abduction >90 degrees
• Innervated by dorsal scapular nerve

Question 25

Rhomboid major

Answer 25

• Originates from spinous processes of T2-T5 vertebrae
• Inserts onto medial border of scapula
• Action = retracts scapula and rotates medial border, helps return arm to original position after abduction >90 degrees
• Innervated by dorsal scapular nerve

Question 26

What are the intrinsic muscles of the shoulder?

Answer 26

• Deltoid
• Teres major
• Supraspinatus
• Infraspinatus
• Subscapularis
• Teres minor

Question 27

Teres major

Answer 27

• Originates from inferior angle of scapula
• Inserts onto medial lip of intertubercular groove of humerus
• Action = adduction and extension of arm at shoulder, medially rotates arm
• Innervated by lower subscapular nerve

Question 28

Supraspinatus

Answer 28

• Originates from supraspinatus fossa of the scapula
• Inserts onto the greater tubercle of the humerus
• Actions = abducts the arm from 0-15 degrees
• Innervation = suprascapular nerve

Question 29

Infraspinatus

Answer 29

• Originates from infraspinous fossa of scapula
• Inserts onto greater tubercle of humerus
• Action = laterally rotates arm
• Innervation = suprascapular nerve

Question 30

Subscapularis

Answer 30

• Originates from subscapular fossa on scapula
• Inserts onto lesser tubercle of humerus
• Action = medially rotates arm
• Innervation = upper and lower subscapular nerves

Question 31

Teres minor

Answer 31

• Originates from posterior surface of scapula
• Inserts onto greater tubercle humerus
• Action = laterally rotates arm
• Innervation = axillary nerve

Question 32

Biceps brachii (long head)

Answer 32

• Origin is supraglenoid tubercle of scapula
• Combines with short head to insert onto radial tuberosity via biceps tendon and deep fascia of forearm
• Action = strong supinator of forearm and flexion of arm at elbow and shoulder joints
• Innervation = musculocutaneous nerve

Question 33

Biceps brachii (short head)

Answer 33

• Origin is coracoid process of scapula
• Combines with long head to insert onto radial tuberosity via biceps tendon and deep fascia of forearm
• Action = strong supinator of forearm and flexion of arm at elbow and shoulder joints
• Innervation = musculocutaneous nerve

Question 34

Coracobrachialis

Answer 34

• Origin is coracoid process of scapula
• Insertion is medial side of the humeral shaft
• Action = flexes arm at shoulder and is a weak adductor of the arm
• Innervation = musculocutaneous nerve

Question 35

Brachialis

Answer 35

• Origin is anterior surface of distal half of humeral shaft
• Insertion is coronoid process of the ulna and ulnar tuberosity
• Action = flexes forearm at the elbow
• Innervation = musculocutaneous nerve with contributions from the radial nerve (C5 and C6)

Question 36

What are the origins of the three heads of the triceps brachii?

Answer 36

1. Long head - infraglenoid tubercle of the scapula
2. Lateral head - shaft of humerus superior to the radial groove
3. Medial head - shaft of humerus inferior the the radial groove

Question 37

Triceps brachii (minus origins)

Answer 37

• Inserts onto olecranon of the ulna
• Action = extends forearm at elbow
• Innervation = radial nerve