Quick Revision: Upper arm is divided into two compartments: 1. Anterior Compartment: Contains three muscles (Biceps brachii, Coracobrachialis, Brachialis). Innervated by Musculocutaneous nerve. 2. Posterior Compartment: Contains one muscle (Triceps brachii) which has three heads. Innervated by radial nerve. Median Nerve: Originates from the medial & lateral cord of brachial plexus. It passes along the anterior compartment of the upper arm and continues to pass anterior to the medial epicondyle of humerus entering the cubital fossa. Relations to the brachial artery: L ateral: in the upper part. A nterior: in the middle part. Medial: in the lower part. In the upper part it is superficial, but in the lower part it is deep to the bicipital aponeurosis. Median nerve supplies NOTHING in the upper arm. Notice that both ulnar nerve & median nerve supply nothing in the upper arm. Posterior compartment of the arm: Contains one muscle (Triceps brachii) that has three heads. 1
Triceps brachii: (look at the radial nerve figure on page 3) Origin: Long head originates from infraglenoid tubercle of scapula. Lateral head originates from the upper half of the posterior surface of humerus superior to the radial groove. Medial head originates from the lower half of the posterior surface of humerus inferior to the radial groove. The three heads converge to form one tendon. Insertion: Olecranon process of Ulna. Function: Triceps is the prime & only extensor of the elbow joint. Nerve supply: Radial nerve. Arterial supply: Profunda brachii artery. Remember: Olecranon is the largest process of Ulna. Triangular Interval: It is a triangular space located in the posterior compartment of the upper arm. Boundaries: Superior: Teres major. Lateral: Shaft of humerus. Medial: Long head of triceps brachii. Contents: Radial nerve. Profunda brachii artery. Profunda brachii vein. 2
Radial nerve: Originates from the posterior cord of brachial plexus, from all the posterior divisions. Course: It passes anterior to subscapularis & teres major & latissimus dorsi muscles reaching the medial side of humerus. It enters the posterior compartment of the upper arm behind humerus by passing through the triangular interval. Radial nerve gives branches in the axilla that innervate long & medial heads of triceps brachii before it reaches them. BUT: within the radial groove it also gives branches that innervate lateral & medial heads of triceps brachii. It pierces the lateral intermuscular septum, entering the anterior compartment of the upper arm exactly anterior to the lateral epicondyle of humerus. It continues downward into the cubital fossa entering the forearm where it gives the posterior cutaneous nerve of the forearm. Remember: Cutaneous nerves of the forearm: Lateral Cutaneous nerve of the forearm >> from musculocutaneous nerve. Medial Cutaneous nerve of the forearm>> from the medial cord of brachial plexus. Posterior Cutaneous nerve of the forearm>> from the radial nerve. 3
Notice that: Passing anterior to the lateral epicondyle >> Radial nerve. Passing anterior to the medial epicondyle >> Median nerve. Passing posterior to the medial epicondyle >> Ulnar nerve. Nerves related to humerus: Axillary nerve: At the upper part of humerus. Originates from the posterior cord of brachial plexus. Wind around surgical neck of humerus. Clinical Application: Fracture of the surgical neck of humerus: Axillary nerve will be involved. As a result, Deltoid muscle will be involved >>> the patient won t be able to abduct his arm 15-90. Teres minor muscle will also be involved. Radial nerve: Passes obliquely within the radial groove. Passes anterior to the lateral epicondyle of humerus. Ulnar nerve: Passes posterior to the medial epicondyle of humerus. Carpal (wrist) Bones: They are eight small bones arranged in two rows: proximal & distal. Each row consists of four bones. These small bones articulate with each other by synovial joints. They concave anteriorly (convex posteriorly) forming the carpal arch. 4
They can be fractured when we fall on out stretched hands. Proximal row bones: (lateral to medial) Scaphoid. Lunate. Triquitrum. Pisiform: it is overriding on the Triquitrum. Distal row bones: (lateral to medial) Trapezium. Trapezoid. Capitate. Hamate, which has a hook. (ham = hook) Carpal Tunnel: Flexor retinaculum: (retinaculum = band) It is a thickened band of deep fascia attached to the carpal bones like a bridge converting the anterior aspect of them (the carpal arch) into a tunnel that transmits: 9 muscles. Median nerve. 5
Clinical Application: Carpal tunnel syndrome: It is a direct effect of increased pressure on median nerve, caused by overuse and swelling of tendons which leads to compression (shortening & thickening) of the flexor retinaculum on the underlying structures, mainly the median nerve. Patients report numbness in the hand, or he\she might not feel his\her hand at all. Treatment includes surgical decompression of the flexor retinaculum (incising then connecting flexor retinaculum by a fibrous tissue as the dr. said) Metacarpal bones: (meta = after) They are five in number, named from lateral to medial: first to fifth. Each of them is a long bone that consists of: a base, a shaft, and a head Direct blow causes fracture in metacarpal bones. Phalanges bones: They are distal to metacarpals. In each of the medial four fingers there are three phalanges: proximal, middle, and distal. The thumb has only two phalanges: proximal and distal. Each phalanx is a long bone that consists of: a base, a shaft, and a head. Cubital fossa: It is a triangular passageway anterior to the elbow between the upper arm and the forearm. Borders: 6
Medial: Pronator teres muscle. Lateral: Brachioradialis Base: Interepicondylar line. Floor: formed by two muscles: Brachialis muscle. Supinator muscle. Contents: (medial to lateral) Median nerve. Brachial artery & it s branches: Ulnar artery Radial artery Tendon of the biceps brachii muscle. Radial nerve & the deep branch of radial nerve. Roof of the cubital fossa (anterior): consists of: Skin. Superficial fascia. Median cubital vein (the most important structure): it connects between cephalic vein & basilic vein. Basilic vein. Cephalic vein. Bicipital aponeurosis. Lateral Cutaneous nerve of the forearm >> from musculocutaneous nerve. Medial Cutaneous nerve of the forearm>> from the medial cord of brachial plexus. Forearm: 7
Forearm is divided by interosseous membrane into two compartments: anterior compartment & posterior compartment. Anterior compartment muscles are flexors. Posterior compartment muscles are extensors. Nerves supply of the anterior compartment: Ulnar nerve & Median nerve. Nerve supply of the posterior compartment: Radial nerve. Muscles of the anterior compartment of the forearm are organized in three layers: Superficial layer: consists of 4 muscles. Middle layer: consists of 1 muscle. Deep layer: consist of 3 muscles. لجنة الدفعة: نرجو من الجميع إرسال أرقامھم لرقم اللجنة و شكرا. 8