TBL5 - Muscles, Nerves and Arteries of Anterior Arm

Question 1

What fasciae are continuous with the brachial fascia? What does the brachial fascia do?

Answer 1

1) The deltoid, pectoral, and axillary fasciae are continuous inferiorly with the brachial fascia
2) The brachial fascia encloses the arm like a snug sleeve

Question 2

Where do the short and long head of the biceps brachii attach proximally? Where do both the short and long head attach distally?

Answer 2

1) The tendon of the long head of the biceps brachii is guided within the intertubercular sulcus to its proximal attachment on the supraglenoid tubercle of the scapula
2) The short head attaches proximally to the coracoid process of the scapula
3) The radial tuberosity is the common distal attachment for both heads

Question 3

What does the biceps brachii do?

Answer 3

1) Supinates forearm and, when it is supine, flexes forearm

2) Short head resists dislocation of shoulder

Question 4

Where is the tendon of the long head of the biceps commonly ruptured and what deformity results?

Answer 4

1) Rupture of the tendon usually results from wear and tear of an inflamed tendon as it moves back and forth in the intertubercular sulcus of the humerus. Typically the tendon is torn from its attachment to the supraglenoid tubercle of the scapula. The rupture is commonly dramatic and is associated with a snap or pop
2) The detached muscle belly forms a ball near the center of the distal part of the anterior aspect of the arm (Popeye deformity)

Question 5

Where does the coracobrachialis attach proximally and distally? What is the function of the coracobrachialis?

Answer 5

1) The coracobrachialis attaches proximally to the tip of the coracoid process of the scapula
2) It attaches distally to the middle third of the medial surface of the humerus
3) Thus, it works synergistically with the anterior part of the deltoid to flex the arm at the shoulder joint when walking

Question 6

Where does the brachialis attach to proximally and distally?

Answer 6

1) The brachialis attaches proximally to the inferior/distal half of the anterior surface of the humerus
2) It attaches distally to the coronoid process and tuberosity of the ulna

Question 7

What is supination of the forearm and hand? What is pronation of the forearm and hand? How are the biceps and brachialis muscles involved in supination and pronation?

Answer 7

1) Supination - rotation of the forearm and hand so that the palm faces forward or upward and the radius lies parallel to the ulna
2) Pronation - rotation of the hand and forearm so that the palm faces backwards or downwards
3) When supinated, the biceps flexes the forearm and when pronated, the biceps becomes the main supinator of the forearm
4) The brachialis muscle flexes the forearm when it is pronated or supinated

Question 8

Where does the lateral pectoral nerve arise from? Where does the musculocutaneous nerve arise from? What structures does the musculocutaneous nerve innervate?

Answer 8

1) The lateral pectoral nerve arises from the side branch of the lateral cord, receiving fibers from C5, C6, C7
2) The musculocutaneous nerve arises from the terminal branch of lateral cord, receiving fibers from C5–C7
3) The musculocutaneous nerve innervates muscles of anterior compartment of arm (coracobrachialis, biceps brachii, and brachialis); skin of lateral aspect of forearm

Question 9

Which spinal cord segments are tested by the biceps tendon reflex?

Answer 9

1) The biceps reflex is one of several deep-tendon reflexes that are routinely tested during physical examinations
2) A positive response confirms the integrity of the musculocutaneous nerve and the C5 and C6 spinal cord segments

Question 10

Where are the medial root and medial cord derived from? What shape is formed by a combination of nerves over the axillary artery?

Answer 10

1) The lateral cord generates the lateral root of the median nerve
2) The medial root of the median nerve arises from the medial cord that continues into the arm as the ulnar nerve
3) The musculocutaneous nerve, median nerve, its lateral and medial roots, and the ulnar nerve create the letter M over the axillary artery

Question 11

Where do the thoracodorsal and subscapular nerves arise from? What does their derivative bifurcate into?

Answer 11

1) The thoracodorsal and subscapular nerves arise from the posterior cord prior to its bifurcation
2) The posterior cord bifurcates into the axillary and radial nerves

Question 12

Where does the axillary nerve originate from? What does the axillary nerve innervate?

Answer 12

1) The axillary nerve originates from the terminal branch of the posterior cord, receiving fibers from C5, C6
2) The axillary nerve innervates the glenohumeral (shoulder) joint, teres minor and deltoid muscles. It also innervates the skin of the superolateral arm (over inferior part of deltoid)

Question 13

Would flexion and supination of the forearm be lost after injury to the musculocutaneous nerve? Where would sensation be lost?

Answer 13

1) A musculocutaneous nerve injury results in paralysis of the coracobrachialis, biceps, and brachialis
2) Flexion of the elbow joint and supination of the forearm are greatly weakened, but not lost. Weak flexion and supination are still possible, produced by the brachioradialis and supinator, respectively, both of which are supplied by the radial nerve
3) Loss of sensation may occur on the lateral surface of the forearm supplied by the lateral antebrachial cutaneous nerve, the continuation of the musculocutaneous nerve

Question 14

How is an affected upper limb positioned after the onset of Erb-Duchenne palsy?

Answer 14

1) As a result of injuries to the superior parts of the brachial plexus (Erb-Duchenne palsy), paralysis of the muscles of the shoulder and arm supplied by the C5 and C6 spinal nerves occurs: deltoid, biceps, and brachialis
2) The usual clinical appearance is an upper limb with an adducted shoulder, medially rotated arm, and extended elbow
3) The lateral aspect of the forearm also experiences some loss of sensation

Question 15

Where does the axillary artery become the brachial artery?

Answer 15

The axillary artery becomes the brachial artery at the inferior border of the teres major muscle

Question 16

What is the profunda brachii artery? Where is the profunda brachii located? Where does the profunda brachii terminate?

Answer 16

1) The profunda brachii artery (deep artery of the arm) is the largest branch of the brachial artery and has the most superior origin (first branch)
2) The profunda brachii accompanies the radial nerve along the radial groove as it passes posteriorly around the shaft of the humerus

Question 17

What does the brachial artery bifurcate into?

Answer 17

In the distal arm, the brachial artery bifurcates into the radial and ulnar arteries that supply the forearm and hand

Question 18

What do the collateral branches of the brachial and profunda brachii arteries anastomose with?

Answer 18

Collateral branches of the brachial and profunda brachii arteries anastomose with recurrent branches of the radial and ulnar arteries

Question 19

What is the role of collateral circulation?

Answer 19

1) Functionally and clinically important peri-articular arterial anastomoses surround the elbow
2) The resulting collateral circulation allows blood to reach the forearm when flexion of the elbow compromises flow through the terminal part of the brachial artery

Question 20

Why is laceration or occlusion of the brachial artery proximal to the profunda brachii artery a surgical emergency?

Answer 20

Although collateral pathways confer some protection against gradual temporary and partial occlusion, sudden complete occlusion or laceration of the brachial artery creates a surgical emergency because paralysis of muscles results from ischemia of the elbow and forearm within a few hours (muscles and nerves can tolerate up to 6 hours of ischemia)

Question 21

Why can the brachial artery be blocked at any level distal to the deep artery of the arm without stopping blood flow to the forearm and hand?

Answer 21

1) Because the arterial anastomoses around the elbow provide a functionally and surgically important collateral circulation, the brachial artery may be clamped distal to the origin of the deep artery of the arm without producing tissue damage
2) The anatomical basis for this procedure is that the ulnar and radial arteries will still receive sufficient blood through the anastomoses around the elbow