Muscles acting at the Elbow Joint

 Bones of the Hand

Flexors and Extensors of the Elbow

• Upper arm is divided into 2 compartments
• Flexors - biceps brachii, brachialis
• Extensor - triceps brachii, anconeus
• Additionally, brachioradialis and pronator teres (in the forearm) can assist with flexion of the elbow.

Pronators and Supinators of the Forearm

• Muscles which pronate
• Pronator teres 
• Pronator quadratus
• Muscles which supinate
• Biceps brachii
• Supinator 

Biceps Brachii

• Fusiform muscle arising from 2 palpable tendons proximally
• Long head - from supraglenoid tubercle and adjacent glenoid labrum (intracapsular and covered in synovial sheath)
• Short head - apex of corocoid process
• Inserts into the posterior ½ of radial tuberosity and into the antebrachial fascia (via bicipital aponeurosis)
• A: Elbow flexion, supination and assists with shoulder flexion
• NS: Musculocutaneous nerve C5,6 

Brachialis

• Covers the front of the elbow-joint and the lower half of the humerus under biceps brachii
• Arises from the lower half of the front of the humerus and adjacent intermuscular septa
• Fibres converge to a thick tendon, which inserts into the tuberosity of ulna and rough depression on the anterior surface of coronoid process
• A: Strong flexor of elbow
• NS: Musculocutaneous nerve (C5,6)

Coracobrachialis

• Evolutionary the only true adductor of the shoulder - grouped with biceps and brachialis due to common nerve supply
• From the tip of the corocoid process
• To roughened area on medial aspect of humerus
• A: Adduction and flexion of GHJ
• NS: Musculocutaneous nerve (C5,6,7)

Brachioradialis

• Usually grouped with the extensors of wrist and digits as found in same compartment and shares common nerve supply
• From upper 2/3s of lateral supracondylar ridge and lateral intermuscular septum
• Forms a flat tendon which attaches to the lateral side of the radial styloid process
• Flexion of elbow - most efficient in mid-prone position
• NS: Radial nerve (C5,6) 

Triceps Brachii

• Found in posterior compartment of arm
• From 3 heads
• Long head - infraglenoid tubercle
• Lateral head - posterior surface of shaft of humerus above spiral groove and lateral IM septum
• Medial head - posterior surface of humerus below spiral groove and medial IM septum
• 3 heads converge to a flat tendon which wraps around olecranon inserting into the upper ½ 
• A: Extension of elbow
• NS: Radial nerve (C7,8) 

Anconeus

• A small triangular muscle found on the back of the elbow-joint
• Appears to be a continuation of the Triceps brachii. 
• Arises by a separate tendon from the back part of the lateral epicondyle of the humerus
• Fibers diverge before inserting  into the side of the olecranon, and upper ¼ of dorsal surface of the body of the ulna
• A: Extension of elbow
• NS: Radial nerve (C7,8)

Pronator Teres

• Arises from 2 heads
• Humeral head - common flexor origin and area immediately above
• Ulnar head - medial border of coronoid process
• Inserts into a roughened area on the lateral aspect midway down the radius
• A: Powerful pronator of the forearm and weak flexor of the elbow
• NS: Median nerve (C6,7) 

Pronator Quadratus

• Works in synergy with pronator teres
• Attaches the lower ¼ of the raduis to ther lower ¼ of the ulna on the anterior aspect
• A: Pronator of the forearm
• Functionally plays an important role in stabilising the bones of the forearm
• NS: Median nerve (anterior interosseous branch) (C8,T1)

Supinator

• Found in the extensor compartment of the forearm - works synergistically with biceps brachii
• Arises from 2 heads
• Humeral head - via tendon from common extensor origin, annular ligament, radial collateral ligament
• Ulnar head - muscular attachment into supinator crest and fossa of ulna
• Inserts into the anterior and lateral surfaces of the upper ½ of the shaft of radius
• A: supination - most important with elbow extended
• NS: Radial nerve (via posterior interosseous nerve) (C5,6)

Bones of the Hand

• Divided into 3 sections:
• Carpus (8) - arranged into 2 rows - scaphoid, lunate, triquetral, pisiform (proximal) and trapezium, trapezoid, capitate, hamate (distal)
• Metacarpals (5)
• Phalanges (14)

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