Lesson 4

Brachium

Brachium - arm

• A. Bony landmarks• 1. humerus

– a. lateral epicondyle - radial side– b. medial epicondyle - ulnar side

• 2. ulna– a. olecranon process – elbow– b. styloid process of ulna - dorsomedial point of wrist

• 3. radius– a. styloid process of radius - lateral point of wrist

• 4. Interosseous membrane: fibrous connective membrane, between radius and ulna

Cutaneous nerves

• (A)1. Medial brachial cutaneous nerve: middle of arm - medial side - to skin over olecranon

• (A) 2. Medial antebrachial cutaneous nerve: appears just inferior to medial brachial nerve on medial arm, splits: – a. anterior branch - skin of anteromedial forearm– b. posterior branch - skin of posteromedial forearm

• (A) 3. Lateral antebrachial cutaneous nerve: continuation of musculocutaneous - appears just above inside of elbow, near cephalic vein- to skin of lateral & anterolateral forearm- also has anterior & posterior branches

• (P) 4. Superior lateral brachial cutaneous nerve - a branch off the axillary nerve- to skin over inferior half of deltoid

Cutaneous nerves

• (P) 5. Posterior brachial cutaneous nerve - branches off the radial nerve up in the axilla- to skin on dorsal arm inferior to deltoid

• (P) 6. Inferior lateral brachial cutaneous nerve = superior terminal branch - of radial nerve- a small branch ~2 inches above lateral epicondyle- to skin of lower lateral & anterolateral arm

• (P) 7. Posterior antebrachial cutaneous nerve = inferior terminal branch of radial nerve - large - appears just below, posterior to lateral epicondyle- to skin on dorsal, lateral forearm

• (P) 8. Superficial radial nerve - lateral border, distal forearm, just proximal to wrist- from under lateral border of brachioradialis- innervates skin on lateral dorsum of hand, thumb, proximal 2/3 of 1st 2-3 fingers(lateral side of middle or ring finger)

• (A) 9. Posterior cutaneous branch of the ulnar nerve: - medial border, distal forearm, just proximal to wrist- innervates skin on medial dorsum of hand, last 2 fingers (medial side of ring finger)

Veins

• 1. cephalic vein: lateral (radial side) - all the way from wrist to deltopectoral groove, to axillary vein

• 2. basilic vein: medial (ulnar side) - goes deep, joins venae comitantes (deep) & brachial artery

• 3. median cubital vein: crosses over, connects cephalic with basilic - common site for drawing blood 

• 4. dorsal venous arch: back of hand - often used for an IV 

Arteries

• Brachial artery: extension/continuation of axillary artery, splits into two terminal branches (radial and ulnar)

• Branches – 1. profunda brachii artery ('deep'): largest, most superior branch;

follows radial nerve- posterior descending branch (splits into radial collateral artery and middle collateral artery)

– 2. two ulnar collateral arteries: branch off brachial below profunda & above elbow - superior ulnar collateral: mid-arm; follows ulnar nerve post. to medial epicondyle- inferior ulnar collateral: from ~2 in. proximal to elbow, anterior to medial epicondyle

Artery• 3. radial artery: lateral, anterior to elbow, crosses

anterior to biceps tendon & supinator muscle; overlapped by brachioradialis muscle– radial recurrent: a branch toward lateral epicondyle,

anastomoses with profunda branch• 4. ulnar artery: medial, anterior to elbow, goes

deep to pronator teres muscle – anterior ulnar recurrent – posterior ulnar recurrent– common interosseous artery - divides into anterior and

posterior interosseous arteries (interosseous recurrent artery -- branch off posterior interosseous or common interosseous artery) 

 

Anastomeses

• ** Collateral elbow circulation - is created by anastomoses between recurrents & collaterals:

• including: radial recurrent; ulnar recurrents (anterior & posterior) ulnar collaterals (superior & inferior), recurrent interosseous and descending branch of profunda brachii

Coracobrachialis

• ORIGINapex of coracoid process of scapula

• INSERTIONmedial surface of middle of shaft of humerus, opposite deltoid tuberosity

• ACTIONflexes and adducts the shoulder

• NERVEmusculocutaneous - C6, 7

BICEPS BRACHII • ORIGIN

short head: apex of coracoid process of scapulalong head: supraglenoid tubercle of scapula (just above the fossa)

• INSERTIONshort, long heads: tuberosity of radius, and aponeurosis of biceps brachii (laterous fibrosus)

• ACTIONFlexes the shoulder joint, and the long head may assist abduction if the humerus is laterally rotated.With the origin fixed: flexes the elbow, moving forearm towards the humerus and supinates forearmWith insertion fixed: flexes the elbow joint moving the humerus toward the forearm as in pull-up or chinning exercises

• NERVEmusculocutaneous nerve - C5, C6

BRACHIALIS

• ORIGINhumerus - distal 1/2, anterior surface of humerus, and medial and lateral intermuscular septa

• INSERTIONulna - coronoid process, ulnar tuberosity

• ACTIONWith origin fixed: flexes the elbow joint moving the forearm toward the humerusWith insertion fixed: flexes the elbow joint moving the humerus toward the forearm as in pull-up or chinning exercises. 

• NERVEmusculocutaneous nerve + a small branch of radial nerve - C5, C6

TRICEPS

• ORIGIN– long head: scapula - infraglenoid tubercle– lateral head: humerus - lateral and posterior

surfaces of proximal 1/2 of humerus; and lateral intermuscular septum

– medial head: humerus - distal 2/3 of medial and posterior surfaces of humerus below the radial groove, and from medial intermuscular septum

• INSERTIONulna - posterior surface olecranon process; antebrachial fascia

• ACTIONextends the elbow joint; long head also assist  in abduction and extension of the shoulder joint

• NERVEradial nerve - C6, C7, C8, T1

ANCONEUS

• ORIGINhumerus - lateral epicondyle; on posterior surface

• INSERTIONulna - olecranon process, on lateral side; & proximal 1/4 of ulna, posterior surface

• ACTIONextends the elbow joint, and may stabilize the ulna during pronation and supination 

• NERVEradial nerve - C7, C8, T1