Upper arm

Question 1

Coracobrachialis muscle

Answer 1

Origins
Coracoid process of the scapula
Insertions
Anteromedial surface of the humerual shaft
Innervation
Musculocutaneous nerve (C5- C7)
Function
Adduction and flexion of the arm at the shoulder joint

Question 2

Clinical correlation of coracobrachialis

Answer 2

The overuse of the coracobrachialis can lead to a hardening of the muscle. Common causes include, among others, bench pressing with extremely heavy weights and carrying heavy loads with hanging arms. Typical symptoms are pain in the arm and shoulder, radiating down to the back of the hand.

In more severe cases the musculocutaneous nerve, which goes through the coracobrachialis, can even get trapped (entrapment). Clinically the affected patients show skin sensation disturbances on the radial part of the forearm and a weakened flexion in the elbow, as the nerve also supplies the biceps brachii and brachialis muscles. In contrast, an actual rupture of the coracobrachialis is extremely rare and almost only occurs in serious accidents.

Question 3

Bicep brachii

Answer 3

Origin
Short head - Apex of the Coracoid process of the scapula

Long head - Supraglenoid tubercle of the scapula

Mnemonic: ‘You walk Shorter to a street Corner. You ride Longer on a Superhighway’

Insertion
Radial tuberosity of the radius

Deep fascia of forearm (insertion of the bicipital aponeurosis)

Innervation
Musculocutaneous nerve (C5- C6)
Blood supply
Branches of brachial artery 
Function
Flexion and supination of the forearm at the elbow joint, weak flexor of the arm at the glenohumeral joint

Question 4

Medial and lateral bicipital grooves

Answer 4

The biceps brachii lies superficial to the brachialis and coracobrachialis muscles, and essentially forms the anterior side of the arm. While both its origin tendons are covered by the deltoid, its insertion tendon can be easily seen and palpated at the crook of the arm.

The space between the biceps and triceps forms two grooves (medial and lateral bicipital grooves). Within the medial bicipital groove course the brachial artery and both the ulnar and median nerves. The lateral bicipital groove contains the radial nerve.

Question 5

Clinical notes of bicep brachii

Answer 5

In physical examination, the biceps plays an important role. It provides an orientation for the palpation of the brachial artery. Hereby the artery is pushed with the fingertips against the humerus in the medial bicipital groove. Furthermore it serves as a reference muscle for the nerve roots C5 and C6. In this exam the biceps reflex is tested by striking the insertion tendon with a hammer and thus activating a contraction of the muscle.

Due to the close relationship between the long biceps tendon and the rotator cuff, inflammatory and degenerative processes often affect each other. Common consequences are a pulley lesion or biceps tendinitis. A pulley lesion is characterized by damage to the biceps pulley complex through which the long biceps tendon is no longer secured in the shoulder joint and thus slips out of the intertubercular sulcus.

A biceps tendinitis is an inflammation of the long biceps tendon often caused by a bursitis or other tendinitides involving the rotator cuff, more rarely through overuse. In severe cases the tendon can even tear apart completely (biceps tendon rupture).

Question 6

Brachialis muscle

Answer 6

Origin
Distal half of anterior surface of humerus

Insertion
Coronoid process of the ulna; Tuberosity of ulna
Innervation
Musculocutaneous nerve (C5,C6); Radial nerve (C7)
Blood supply
Brachial artery, radial recurrent artery, (occasionally) branches from the super and inferior ulnar collateral arteries
Functions
Strong flexion of forearm at the elbow joint

The brachialis muscle originates from the anterior surface of the distal half of the humerus, just distal to the insertion of the deltoid muscle. It is also attached to the intermuscular septa of the arm on either side, with a more extensive attachment to the medial intermuscular septum.

The fibers of brachialis extend distally to converge on a strong tendon. The tendon inserts onto the tuberosity of ulna and onto a rough depression on the anterior surface of the coronoid process of the ulna–passing between two slips of the flexor digitorum profundus muscle. It sometimes has an accessory attachment to the radius or the bicipital aponeurosis.

Question 7

Clinical notes of brachialis

Answer 7

The brachialis can be clinically assessed by palpating the contracting muscle fibers during flexion of the elbow joint against resistance while the forearm is in the semi-prone position. If acting normally, the brachialis can be seen and palpated during this movement. If the muscle cannot be palpated, testing of the function of the muscle can be used to assess it. This can present as a weakness when flexing the arm against resistance, but also as an inability to fully extend the elbow joint due to painful stretching of the brachialis tendon.

The brachialis is the main muscle acting in common upper body exercises such as pull ups and elbow curls and overuse of it during exercises such as these can cause inflammation in the tendon of the muscle. This is called brachialis tendonitis. Climbers elbow is a form of brachialis tendonitis that is extremely common in climbers. It is caused by forceful contractions of the brachialis muscle, especially when the elbow is hyperextended. A common cause of this injury in climbers is reaching (hyperextending the elbow) and then pulling their body weight upwards by flexing the elbow joint, such as in rock climbing.

Question 8

Cubital Fossa

Answer 8

Shallow triangular depression anterior to the elbow joint

Boundaries:
Superior - horizontal line joining medial and lateral epicondyles
Laterally - brachioradialis
Medially - pronator teres
Floor - brachialis and supinator
Roof - joining of brachial and forearm fascia plus brachial aponeurosis

Contents:

Within overlying subcutaneous tissue:

1. Median cubital vein
2. Medial and lateral cutaneous nerves of forearm following the basilic and cephalic veins

Within the cubital fossa:

1. Median nerve
2. Brachial artery
3. Bicep brachii tendon
4. Radial nerve (deep and superficial braches)