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University of Connecticut School of Medicine Human Anatomy Module

Learn: Arm

ARM

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     Biceps brachii muscle

Origin Long head: supraglenoid tubercle of scapula
Short head: apex of coracoid process
Insertion Radial tuberosity
Innervation Musculocutaneous nerve
Artery Brachial artery (muscular branches)
Action Flexes forearm at elbow joint; supinates forearm; accessory flexor of arm at glenohumeral joint
Biceps brachii

     Brachialis muscle

Origin Anterior aspect of humerus (medial and lateral surfaces) and adjacent intermuscular septae
Insertion Tuberosity of the ulna
Innervation Musculocutaneous nerve
Artery Brachial artery (muscular branches), recurrent radial artery
Action Flexes the forearm at the elbow joint
Brachialis

     Coracobrachialis muscle

Origin Apex of coracoid process
Insertion Middle third of medial surface of humerus
Innervation Musculocutaneous nerve
Artery Brachial artery (muscular branches)
Action Helps in flexion and adduction of arm
Coracobrachialis

     Triceps brachii muscle

Origin Long head: infraglenoid tubercle
Lateral head: posterior surface of humerus
Medial head: posterior surface of humerus
Insertion Olecranon of ulna
Innervation Radial nerve
Artery Profunda brachii artery
Action Extends forearm at elbow joint. Long head also can extend and adduct the arm at the shoulder joint.
Triceps brachii

     Anconeus muscle

Origin Lateral epicondyle of humerus
Insertion Olecranon and proximal posterior surface of ulna
Innervation Radial nerve
Artery Middle collateral branch of deep brachial artery; Recurrent interosseous artery
Action Abduction of the ulna in pronation; accessory extensor of the elbow joint
Anconeus

Nerves

Relatively speaking, there is not that much to know in terms of nerves in the arm. The few nerves that are relevant here include:

  1. Musculocutaneous nerve
    1. Comes off of lateral cord of brachial plexus
    2. Pierces and innervates coracobrachialis muscle
    3. After piercing the coracobrachialis muscle, it descends in between the biceps brachii and brachialis muscles and provides motor innervation to both of them
    4. Passes the elbow, pierces deep fascia, and becomes the lateral cutaneous nerve of the forearm (also called lateral antebrachial cutaneous nerve)
  2. Radial nerve
    1. Comes off of posterior cord of brachial plexus
    2. Passes through triangular interval with profunda brachii artery and travels down the posterior compartment of the arm, initially between long and medial heads of triceps brachii muscle and later between medial and lateral heads of triceps brachii muscle, in the radial groove of the humerus
      1. Provides motor innervation to triceps brachii muscle
    3. After piercing lateral intermuscular septum of arm, passes anterior to lateral epicondyle of humerus between brachialis and brachioradialis muscles. Enters cubital fossa, where it divides into superior and deep branches.
    4. Gives off posterior cutaneous nerve of arm, inferior lateral cutaneous nerve of arm, and posterior cutaneous nerve of forearm
    5. Provides motor innervation to posterior compartment of forearm
    6. Provides cutaneous innervation to dorsum of hand
  3. Medial cutaneous nerve of the arm
    1. Comes from medial cord of brachial plexus
    2. Cutaneous innervation to anteromedial skin of arm

Arteries

  1. Brachial artery
    1. Continuation of the axillary artery after it crosses the inferior border of the teres major muscle
    2. Branches
      1. Profunda brachii artery (deep artery of the arm)
        1. Often forms an anastamosis with the posterior humeral circumflex artery
        2. Upon termination, divides into middle collateral artery and radial collateral artery
      2. Superior ulnar collateral artery
      3. Inferior ulnar collateral artery
    3. At elbow, divides into radial artery and ulnar artery

Quiz

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