📚 Question Bank

Correct Answer: C

From the deep surface of the brachial fascia, two strong walls of connective tissue grow inward and attach directly to the humerus bone. These are the medial and lateral intermuscular septa. They effectively divide the arm into two isolated compartments: anterior (flexor) and posterior (extensor).

Correct Answer: C

To act on a joint, a muscle must cross it. The medial and lateral heads of the triceps both originate on the shaft of the humerus, so they only cross the elbow.

The long head originates all the way up on the infraglenoid tubercle of the scapula, allowing it to act on the shoulder and elbow.

Correct Answer: D

After supplying the biceps and brachialis, the musculocutaneous nerve emerges on the lateral side of the biceps and becomes the lateral cutaneous nerve of the forearm. Therefore, a high lesion will wipe out sensation on the skin of the lateral (radial) side of the forearm.

Correct Answer: B

The basilic vein starts superficially on the medial side of the forearm. Around the midpoint (middle third) of the arm, it dives deep, piercing the brachial fascia to travel alongside the brachial artery.

Correct Answer: C

The radial nerve leaves the axilla and enters the posterior compartment by diving into the spiral groove of the humerus. It is accompanied by the profunda brachii artery (the deep artery of the arm). They are both highly vulnerable in mid-shaft humeral fractures.

Correct Answer: B

When you pronate your forearm (palm down), the radius crosses over the ulna, which twists and mechanically disadvantages the biceps tendon. In this position, if you try to flex your elbow, the brain recruits the brachialis (which attaches to the stationary ulna) to do almost all the heavy lifting.

Correct Answer: C

In the upper half of the arm, the ulnar nerve travels in the anterior compartment. In the middle of the arm, it pierces the medial intermuscular septum to move into the posterior compartment. An anteromedial approach right at this transition zone puts the ulnar nerve directly at risk.

Correct Answer: C

When a child suffers a supracondylar fracture, the sharp bone fragments can impale or spasm the brachial artery, cutting off blood supply to the forearm. If not fixed rapidly, the flexor muscles die (necrosis) and turn into rigid scar tissue, permanently curling the hand into a claw-like contracture known as Volkmann's.

Correct Answer: B

The superior ulnar collateral artery branches off the brachial artery and travels down behind the medial epicondyle. Coming up from below to meet it is the posterior ulnar recurrent artery. Together they form an anastomotic loop behind the inner elbow.

Correct Answer: B

It goes from the coracoid process (anteriorly and medially on the scapula) to the medial shaft of the humerus. When it shortens, it pulls the arm forward (flexion) and pulls it in toward the body (adduction).

Correct Answer: B

The long head of the biceps has a stressful path traveling through the shoulder joint. When it snaps, the proximal anchor is lost, and the entire muscle belly retracts and bunches up down near the elbow, creating a prominent bulge resembling Popeye's arm.

Correct Answer: B

The radial nerve is massive. As the terminal branch of the posterior cord, it is responsible for extending almost everything in the upper limb (elbow, wrist, fingers). Because it has such a widespread job, it draws nerve fibers from every single root of the brachial plexus: C5, C6, C7, C8, and T1.

Correct Answer: D

Before the radial nerve enters the spiral groove, it gives off the posterior cutaneous nerve of the arm, which supplies the skin over the back of the triceps. A high radial nerve lesion will result in numbness on the back of the arm.

Correct Answer: C

This is a trick question! Both heads originate from the scapula, bypassing the humerus completely.

• The short head originates from the coracoid process.
• The long head originates from the supraglenoid tubercle.

Correct Answer: B

The brachial artery and the median nerve travel right down the middle of the anterior arm, directly over the front of the distal humerus before crossing the elbow. If the distal piece of the humerus breaks and gets shoved forward and inward (anteromedial), those sharp bone spikes will plow directly into them.

Correct Answer: B

Strong elbow extension means the triceps muscle is working. The nerves to the triceps branch off the radial nerve high up in the axilla. Complete wrist drop means all forearm extensors are dead. Therefore, the lesion must be trapped exactly in the middle—in the radial groove of the humerus.

Correct Answer: B

Around the mid-arm, the ulnar nerve pierces the medial intermuscular septum to run in the posterior compartment. Because it has left the anterior 'room', an anterior injection will fail to bathe the ulnar nerve.

Correct Answer: B

In the very upper part of the arm, the neurovascular bundle (brachial artery and median nerve) is tucked underneath and behind the coracobrachialis muscle. A ruptured vessel here will cause a high-pressure hematoma within this muscle's tough fascial sheath, compressing the median nerve.

Correct Answer: D

If the brachial artery is blocked very high up, blood must detour through the deep system. Blood will flow down the profunda brachii into its posterior branch, the middle collateral artery. This connects to the interosseous recurrent artery coming up from the posterior forearm, providing a vital deep bypass circuit.

Correct Answer: C

The biceps is biomechanically disadvantaged when the forearm is pronated because its tendon is wrapped around the radius. The brachialis, inserting on the ulna, is unaffected by forearm rotation and provides almost all the flexion force in this scenario.

Correct Answer: B

If hand motor function is completely normal, the main ulnar nerve is likely fine. The injury is likely to the medial cutaneous nerve of the forearm, a separate sensory branch from the medial cord that supplies sensation to the medial aspect of the forearm and hand, leaving hand movement pristine.

Correct Answer: B

When you dislocate your elbow backward, the forearm bones go posterior, driving the rounded distal end of the humerus violently forward. The median nerve gets stretched incredibly tight over this protruding bone, leading to a traction injury.

Correct Answer: C

The main nutrient artery that feeds the inner marrow cavity of the humerus typically branches directly off the main brachial artery around the middle of the arm. It dives into a small hole (nutrient foramen) on the anteromedial surface.

Correct Answer: B

The triceps is heavily C7 dependent. However, the radial nerve branches to the anconeus (a small accessory extensor at the elbow) sometimes carry fibers from C8 or T1, allowing it to provide weak, residual extension even if C7 is damaged.

Correct Answer: A

The biceps is innervated by the musculocutaneous nerve. Forearm pronation is driven by the median nerve. The lateral cord of the brachial plexus splits to become the musculocutaneous nerve AND the lateral root of the median nerve, perfectly explaining both deficits.