DR2. Arm and brachial plexus

Question 1

How many flexor muscles are found in the anterior compartment of the arm

Answer 1

Three flexor muscles are found in the anterior compartment of the arm. One of these
muscles is a flexor at the shoulder joint, one a flexor at the elbow joint, and the third is a flexor at both the shoulder and elbow joint.

Question 2

Largest muscle in the anterior compartment

Answer 2

• Biceps brachii

Question 3

Biceps brachii - origin

Answer 3

• The long head has an origin from the supraglenoid tubercle of the scapula, and the short head from the coracoid process of the scapula

Question 4

Path of the long head of biceps brachii

Answer 4

• Long head emerges out of the joint capsule and continues down the intertubercular sulcus(bicipital groove)

Question 5

What do the two heads of biceps brachii unite to form

Answer 5

• Unite to form a large muscle that inserts by a flattened tendon into the tuberosity of the radius

Question 6

What is the bicipital aponeurosis and what is its path

Answer 6

• An expansion of the tendon of the biceps
• It crosses medially over the superficial flexors of the forearm and attaches to the posterior border of the ulna via the deep fascia

Question 7

Biceps - action

Answer 7

• As biceps crosses both the shoulder joint and the elbow joint, it exerts its flexor action on both joints
• Biceps is also a very powerful supinator of the forearm

Question 8

Coracobrachialis - origin

Answer 8

• Coracoid process

- Short head of biceps and the tendon of coracobrachialis have a common origin which forms a conjoint tendon

Question 9

Coracobrachialis - insertion

Answer 9

• Medial aspect of the humerus half way down the shaft

Question 10

Brachialis - origin

Answer 10

• Origin from the distal half of the anterior of the humerus

Question 11

Brachialis - insertion

Answer 11

• Inserts into the ulna tuberosity

Question 12

Triceps brachii - origin

Answer 12

• Long head has an origin from the infraglenoid tubercle of the scapula
• The lateral head from the posterior aspect of the humerus above the spiral or radial groove of the humerus
• The medial head again from the posterior surface of the humerus but below the spiral groove

Question 13

Triceps brachii - insertion -

Answer 13

• The three heads unite to insert into the olecranon process of the ulna

Question 14

Brachial plexus - nerve roots

Answer 14

• C5, C6, C7, C8 and T1

Question 15

Brachial plexus - trunks

Answer 15

• Superior (or upper), middle and inferior (or lower)

Question 16

Brachial plexus - cords

Answer 16

• Lateral, medial and posterior (due to their relationship with axillary artery)

Question 17

What does the lateral cord give rise to

Answer 17

• Lateral pectoral nerve

- Terminal branches of the lateral cord are the lateral head of the median nerve and the musculocutaneous nerve

Question 18

Where does the musculocutaneous nerve pierce coracobrachialis

Answer 18

• Approx 5cm distal to the conjoint tendon

Question 19

Terminal branch of musculocutaneous nerve and what does it innervate

Answer 19

• Lateral cutaneous nerve of the forearm, which supplies the skin of the lateral forearm on both the dorsal and ventral aspects

Question 20

What does the medial cord give rise to

Answer 20

• Medial pectoral nerve
• Cutaneous nerves of the arm and forearm
• The terminal branches of the medial cord are the medial head of the median nerve and the ulnar nerve

Question 21

What does the ulnar nerve innervate

Answer 21

• Gives a limited supply to the flexor muscles of the forearm and is the main supply to the small muscles of the hand

Question 22

Location of ulnar nerve

Answer 22

• Lies medial to the brachial artery in the arm and passes behind the medial epicondyle of the humerus at the elbow joint (the cubital tunnel) to gain access to the forearm
• It can easily be damaged at the region of the medial epicondyle. At this point, if it is hit, it may cause shooting sensation that radiates down the forearm to the little and ring fingers

Question 23

What does the median nerve receive contributions from

Answer 23

• Receives contributions from both lateral and medial cords

Question 24

What does the median nerve innervate

Answer 24

• Supplies almost all of the muscles of the anterior compartment of the forearm

Question 25

Path of the median nerve

Answer 25

• It crosses in front of the axillary artery to pass distally under cover of biceps into the forearm

Question 26

What does the posterior cord give rise to

Answer 26

• Upper subscapular, thoracodorsal and lower subscapular nerves
• The terminal branches of the posterior cord are the radial nerve and the axillary nerve

Question 27

What do the upper subscapular, thoracodorsal and lower subscapular nerves innervate

Answer 27

• These nerves supply the subscapularis, teres major and latissimus dorsi muscles

Question 28

What does the radial nerve innervate

Answer 28

• Supplies muscles and skin over the whole posterior aspect of the upper limb
• The radial nerve supplies the triceps muscles and the extensor muscles of the forearm

Question 29

Path of the radial nerve

Answer 29

• After passing through the spiral groove, the nerve enters the anterior compartment of the forearm lying under cover of the muscles on the lateral side of the forearm

Question 30

What does the axillary nerve innervate

Answer 30

• Axilllary nerve supplies teres minor and deltoid muscle as well as a small area of skin over the insertion of the deltoid, known as the badge area

Question 31

Borders of quadrangular space

Answer 31

• Formed between the borders of teres minor, teres major, the humerus and the long head of triceps

Question 32

Stem artery of the upper limb

Answer 32

• Subclavian artery

Question 33

Origin of subclavian artery on each side

Answer 33

• On the right side, it is a branch of the brachiocephalic trunk
• On the left side, it normally arises directly off the aorta

Question 34

At what point does the subclavian artery become the axillary

Answer 34

• As it passes over the first rib

Question 35

What is axillary artery accompanied by in the axilla

Answer 35

• Cords of the brachial plexus

Question 36

At what point does the axillary artery become the brachial

Answer 36

• Once the axillary artery crosses the lower border of teres major

Question 37

Important branch of brachial

Answer 37

• The brachial artery gives off many small muscular branches and also the profunda (or deep) brachii artery, which accompanies the radial nerve in the spiral groove of the humerus

Question 38

What does the profunda (or deep) brachii artery supply blood to

Answer 38

• Supplies triceps and the elbow joint