Muscles of the Arm PDF

Muscles of the Arm Mrs. Sichela   The arm is the part of the free upper limb.  It extends between the shoulder and the elbow.  The deep fascia of the arm surrounds it on all sides like a sleeve.  The lateral and m...

Muscles of the Arm Mrs. Sichela   The arm is the part of the free upper limb.  It extends between the shoulder and the elbow.  The deep fascia of the arm surrounds it on all sides like a sleeve.  The lateral and medial intermuscular septa extend from the deep fascia to the humerus to divide the arm into anterior and posterior compartments  The septa are attached to the margins of supracondylar Introduction ridges of the humerus.  The ulnar nerve and superior ulnar collateral artery pierce the medial intermuscular septum to enter the posterior compartment of arm.  The radial nerve and radial collateral artery pierce the lateral intermuscular septum to enter anterior compartment of arm.  The muscles include;  coracobrachialis,  Brachialis  biceps brachii muscles. Nerves include;  The musculocutaneous nerve is the nerve of the Contents of anterior compartment Anterior  The median nerve Compartment  The ulnar nerve travels in the upper half medially  The radial nerve travels in the lower half laterally.  The medial cutaneous nerves of arm and of forearm travel in the compartment until they pierce the deep fascia of the arm.   Vessels Contents of  The brachial artery Anterior Compartment  The brachial veins (venae commitantes) Muscle Origin Insertion Innervation Function Coracobrachialis Apex of coracoid Linear roughening on Musculocutaneous Flexor of the arm at process mid-shaft of humerus nerve [C5,C6,C7] the gleno-humeral on medial side joint Biceps brachii Long head- Radial tuberosity Musculocutaneous Flexor of the forearm supraglenoid nerve [C5,C6] at the elbow joint and tubercle of scapula; supinator of the Short head- apex of forearm coracoid process Accessory flexor of the arm at the glenohumeral joint Brachialis Anterior aspect of Tuberosity of the ulna Musculocutaneous Powerful flexor of the humerus (medial and nerve [C5,C6]; (small forearm at the elbow lateral surfaces) and contribution by the joint adjacent radial nerve [C7] to intermuscular septae lateral part of muscle)   The triceps brachii is the only muscle in the posterior compartment of arm. Contents of  In addition, the compartment contains the Posterior radial nerve and profunda brachii vessels Compartment in the spiral groove and the ulnar nerve in the lower half medially.  Muscle Muscle origin Muscle Innervation Function insertion Triceps brachii Long head- Olecranon Radial nerve Extension of the infraglenoid [C6,C7,C8] forearm at the tubercle of scapula elbow joint. Medial head- Long head can also posterior suface of extend and adduct humerus the arm at the Lateral head- shoulder joint posterior surface of humerus  Brachial artery  The major artery of the arm,  Is found in the anterior compartment  Begins as a continuation of the axillary artery at the lower border of the teres major muscle,  It terminates just distal to the elbow joint Arteries where it divides into the radial and ulnar arteries  Additional branches are the profunda brachii artery and nutrient arteries to the humerus  Superior ulna collateral  Inferior ulnar collateral  Profunda artery  the largest branch of the brachial artery, passes into and supplies the posterior compartment of the arm  It enters the posterior compartment with the radial nerve and together they pass through the triangular interval Arteries Branches  Muscular branches to triceps brachii muscle  Nutrient branch to the humerus.  Deltoid branch ascends to anastomose with a branch of posterior circumflex humeral artery.  Middle collateral artery  Radial collateral artery   Paired brachial veins pass along the medial and lateral sides of the brachial artery, receiving tributaries that accompany branches of the artery  Two large subcutaneous veins, the basilic vein and the cephalic vein, are located in the arm. Veins  The basilic vein passes vertically in the distal half of the arm and becomes the axillary vein at the lower border of the teres major muscle  The brachial veins join the basilic, or axillary vein.  The cephalic vein drains into the axillary vein.  Musculocutaneous nerve  The musculocutaneous nerve provides:  Motor innervation to all muscles in the anterior compartment of the arm  Sensory innervation to skin on the lateral surface of the forearm. Median nerve Nerves  The median nerve has no major branches in the arm  However, branch to one of the muscles of the forearm, the pronator teres muscle, may originate from the nerve immediately proximal to the elbow joint.  Ulnar nerve  The ulnar nerve has no major branches in the arm. Radial nerve  In the arm, the radial nerve has muscular and cutaneous branches;  Muscular branches include those to the  Triceps brachii (posterior compartment of the arm) Nerves  In addition, the radial nerve contributes to the innervation of the lateral part of the brachialis muscle.  Cutaneous branches of the radial nerve that originate in the posterior compartment of the arm are the  Inferior/Lower lateral cutaneous nerve of arm  Posterior cutaneous nerve of forearm,   The elbow joint is a complex joint involving three separate articulations, which share a common synovial cavity:  The joints between the trochlear notch of the ulna and the trochlea of the humerus The Elbow Joint and between the head of the radius and the capitulum of the humerus  Together these are the principal articulations of the elbow joint.  Movements at this joint are flexion and extension of the forearm on the arm   The joint between the head of the radius and the radial notch of the ulna also known as the proximal radio-ulnar joint  Is involved with pronation and supination of the forearm.  The articular surfaces of the bones are The Elbow joint covered with hyaline cartilage.  The synovial membrane originates from the edges of the articular cartilage and lines the radial fossa, the coronoid fossa, the olecranon fossa, the deep surface of the joint capsule, and the medial surface of the trochlea   The fibrous membrane of the joint capsule is thickened medially and laterally to form collateral ligaments, which support the flexion and extension movements of the elbow joint  In addition, the external surface of the joint capsule is reinforced laterally where it cuffs the Ligaments of head of the radius with a strong anular ligament of radius. elbow joint  Although this ligament blends with the fibrous membrane of the joint capsule in most regions, they are separate posteriorly.  The anular ligament of radius also blends with the radial collateral ligament.   It is an important area of transition between the arm and the forearm.  It is triangular intermuscular space seen as a shallow surface depression in front of the elbow. Boundaries  The base: the imaginary line passing through The cubital the medial and lateral epicondyles of humerus. Fossa  The medial boundary: is formed by the lateral margin of pronator teres muscle.  The lateral boundary: is formed by medial margin of brachioradialis muscle.  The apex: is located at the crossing of pronator teres and brachioradialis muscles.  The floor: consists of brachialis in the upper part and supinator in the lower part.  The roof: consists of skin, superficial fascia and deep fascia, which is strengthened by the bicipital aponeurosis.  The latter is crossed superficially by median cubital vein. The bicipital aponeurosis provides a firm platform to steady this vein during venipuncture and to protect the underlying brachial artery and median nerve.   The major contents of the cubital fossa, from lateral to medial, are:  The tendon of the biceps brachii muscle;  The brachial artery; Contents of  The median nerve cubital fossa Other contents  The brachial artery normally bifurcates into the radial and ulnar arteries in the apex of the fossa  The radial nerve lies just under the lip of the brachioradialis muscle, Radial artery  The radial artery leaves the cubital fossa through its apex to enter the front of forearm.  It gives one branch called radial recurrent that takes part in elbow anastomosis. Ulnar artery  The ulnar artery leaves the cubital fossa deep to the ulnar head of pronator teres.  It gives off following important branches in the cubital fossa.  Anterior and posterior ulna recurrent arteries that take part in elbow anastomosis,  The common interosseous artery is another very important branch which divides into anterior and posterior interosseous arteries.  The interosseous recurrent branch ( taking part in elbow anastomosis) arises from posterior interosseous artery.  Anterior Anastomosis Medially  Anterior branch of inferior ulnar collateral (branch of brachial artery)  Anterior ulnar recurrent (branch of ulnar artery) Posterior Anastomosis Medially Elbow  Superior ulnar collateral (branch of brachial artery) anastomosis  Posterior ulnar recurrent (branch of ulnar artery) Anterior Anastomosis Laterally  Radial collateral (branch of profunda brachii artery)  Radial recurrent (branch of radial artery)  Posterior Anastomosis Laterally  Middle collateral (branch of profunda brachii artery)  Interosseous recurrent (branch of posterior interosseous artery) Elbow anastomosis  Functional Importance  This arterial anastomosis ensures the normal circulation to forearm and hand when the elbow is flexed and the brachial artery is compressed temporarily.