Upper Arm Muscles PDF

MSK(101-1) Academic year: 2024/2025 ANATOMY DEPARTMENT Upper arm Prof. Dr. Hayam Elsaady Farhoud  Upper arm The upper arm extends from the shoulder to the elbow. -The upper arm has the following layers: 1. Skin. 2. Superficial fascia: it contains basilic and cephalic veins a...

MSK(101-1) Academic year: 2024/2025 ANATOMY DEPARTMENT Upper arm Prof. Dr. Hayam Elsaady Farhoud  Upper arm The upper arm extends from the shoulder to the elbow. -The upper arm has the following layers: 1. Skin. 2. Superficial fascia: it contains basilic and cephalic veins and also fat. 3. Deep fascia. -Two fascial septa, on the medial and the lateral sides, called medial and lateral intermuscular septa extend from the deep fascia and attach to the medial and lateral supracondylar ridges of the humerus, respectively. - These 2 fascial septa divide the arm into an anterior and a posterior fascial compartments. Compartment of arm The anterior (flexor) compartment contains: Muscles the biceps brachii, coracobrachialis and brachialis muscles, supplied by musculocutaneous nerve. Vessls: Brachial artery & Basilic vein. Nerves: Musculocutaneous nerve, while: Median, Ulnar and Radial nerves passes through anterior compartment. The posterior (extensor) compartment contains Muscles: the 3 heads of triceps (supplied by radial nerve )and subanconeus muscle. Vessels: Profunda Brachii artery and Superior and inferior ulnar collateral arteries Nerves: Radial nerve and Ulnar nerve aneous Nerves of the Upper Arm A)Lateral side of the upper arm: 1. The supraclavicular nerves (C3, C4): the upper 1/2 of the deltoid. 2. The upper lateral cutaneous nerve of the arm (C5, C6): lower 1/2 of the deltoid. 3. The lower lateral cutaneous nerve of the arm (C5, C6): lateral side of the arm below the deltoid. B) Medial side of the upper arm: 1. The intercostobrachial nerve (T2): the upper part of the medial side of the arm close to axilla. 2. The medial cutaneous nerve of the arm (C8& T1): the medial side of the arm below the axilla. C) Back of the upper arm: The posterior cutaneous nerve of the arm (C5, 6, 7, 8): Muscles of the arm Biceps brachii -1 -2 Coracobrachialis Brachialis -3 Triceps -4  Biceps brachii Origin: 1-Short head: arise by a common tendon with coracobrachialis from the tip of coracoid process. 2-Long head: from supra-glenoid tubercle Insertion: (by tendon and aponeurosis): 1- by its tendon into the rough posterior part radial tuberosity 2- by its bicipital aponeurosis into the deep fascia on the upper part of the medial side of the forearm. The aponeurosis intervenes between the median cubital vein (superficial) and the brachial artery (deep). Biceps brachii Nerve supply: musculocutaneous nerve which gives a separate branch to each head. Action: 1- it is powerful supinator of the forearm 2- flexion of the supinated forearm at the elbow joint. 3- the long head support the shoulder joint from above 4-the short head flexion of the arm at shoulder joint. N.B. -The biceps is a particularly powerful supinator of the forearm due to the distal attachment of the muscle at the radial tuberosity. - While the biceps crosses both the shoulder and elbow joints, its main function is at the elbow where it flexes the forearm and supinates the forearm. - Both these movements are used when opening a bottle with a corkscrew: first biceps unscrews the cork (supination), then it pulls the cork out (flexion).  Coracobrachialis Origin: arise by a common tendon with the short head of biceps from the tip of coracoid process. Insertion: into the middle of the medial border of the humerus Nerve supply: by the musculocutaneous nerve which supplies the muscle before piercing it. Action: it helps in flexion of the arm at the shoulder joint Relations at the insertion of coracobrachialis: Median nerve: crosses the brachial artery from lateral to medial. Radial nerve: pierces the lateral intermuscular septum after leaving the spiral groove to enter the anterior compartment. Ulnar nerve: pierces the medial intermuscular septum to enter the posterior compartment Basilic vein: pierces the deep fascia to ascend medial to the brachial artery. Nutrient artery: enters the nutrient foramen in the humerus  Brachial is Origin: arise from the lower ½ of the anterior surface of the humerus deep to the biceps. Insertion: into the tuberosity of the ulna on the anterior surface of the coronoid process of the ulna. (The biceps is inserted into the radius, while the brachialis is inserted into the ulna). Brachialis Nerve supply: 1-musculocutaneus nerve 2- radial nerve Action: flexion of the forearm at the elbow joint. (the main flexor of the elbow with the forearm either supinated or pronated). * Nerves related to brachialis: Radial nerve: on its lateral side Median nerve: on its anterior surface. Musculocutaneous nerve: on its anterior surface between it and the biceps.  Trice ps the only muscle on the back of the humerus, correspond to the brachialis and biceps. Origin: 1- long head: arise from infraglenoid tubercle. 2- medial head: lower ½ of the posterior surface of the humerous below the spiral groove. (corresponds to the origin of brachialis). 3-lateral head: from the upper lip of the spiral groove. It descends over the groove to form its roof. N.B. Medial head: deeper to the other 2 heads, Long head: superficial and medial and Lateral head superficial and lateral. Insertion: the 3 heads fuse together above the elbow and are inserted into the top of the olecranon process of the ulna. Nerve supply: radial nerve 1- long head: gets its branch in the axilla. 2- medial head: gets its branch immediately before the radial nerve inter the spiral groove and gets one the spiral groove 3-lateral head: gets its branch in the spiral groove. Action: extension of the forearm at the elbow joint. Articularis cubiti (subanconeus) It consists of the few deep fibres of the lower part of triceps Insertion: into the posterior part of the capsule of the elbow joint. Nerve supply: radial nerve. Action :Articularis cubiti pulls the capsule of the elbow during its extension, preventing its crushing. Nerves of Anterior Compartment of the Arm 1) Musculocutaneous Nerve (C5, 6 and 7) -It is a mixed nerve. - It arise from the lateral cord of the brachial plexus (C5, 6, and 7) in the axilla. Course and relations: - It runs downward and laterally, -pierces the coracobrachialis muscle Then passes downward between the biceps and brachialis muscles. -It appears at the lateral margin of the biceps tendon - pierces the deep fascia just above the elbow joint and becomes the lateral cutaneous nerve of the forearm. Branches: 1) Muscular branches to supply the biceps, coracobrachialis and brachialis 2) Articular branches to supply the elbow joint. 3) Cutaneous branches: the lateral cutaneous nerve of the forearm which divides into anterior and posterior branches to supply the skin of the front and lateral aspects of the forearm down to the root of the thumb. Injury to Musculocutaneous Nerve Injury to the musculocutaneous nerve in the axilla is usually inflicted by a weapon as a knife. 1- Motor effect: paralysis of the coracobrachialis, biceps, and brachialis; consequently, flexion of the elbow and supination of the forearm are greatly weakened. 2-Sensory effect: Loss of sensation may occur on the lateral surface of the forearm supplied by the lateral cutaneous nerve of the forearm. Vessels of Anterior Compartment of the Upper Arm Brachial Artery -It begins at the lower border of the teres major muscle as a continuation of the axillary artery. -It terminates in front of the neck of the radius by dividing into the radial and ulnar arteries. - It is accompanied by 2 venae comitantes. -Course: It descends downwards and laterally, at first it is medial to the humerus, Relations of brachial artery: 1-In upper 1/2 of the arm: -Anteriorly: skin and fasciae. -Posteriorly: radial nerve separates it from long head of triceps. -Laterally: median nerve, coracobrachialis and short head of biceps. -Medially: ulnar nerve, basilic vein and medial cutaneous nerve of forearm. 2- At middle of arm (at insertion of coracobrachialis): - Median nerve crosses the artery from lateral to medial (in front or behind the artery). 3- In lower 1/2 of the arm: - Anteriorly: skin and fasciae. - Posteriorly: brachialis, separate it from the humerus. - Laterally: biceps muscle. - Medially: median nerve. 4-In the cubital fossa: - Anteriorly: skin and fasciae, bicipital aponeurosis and median cubital vein. - Posteriorly: tendon of brachialis muscle. - Laterally: tendon of biceps muscle. - Medially: median nerve. Branches of Brachial Artery Branches of Brachial Artery : 1) Profunda brachii artery (largest branch): 2) Superior ulnar collateral artery: 3) Inferior ulnar collateral artery: 4) Nutrient artery 1)Profunda brachii artery: 5) a) Muscular Ascending branches branch (deltoid branch)----------- descending branch of posterior circumflex humeral artery b) Anterior descending branch (radial collateral)-------------- anastomosing with radial recurrent artery. c) Posterior descending branch (middle collateral)--------------interosseous recurrent artery. 2) Superior ulnar collateral artery: d) Muscular branches: It anastomoses to ulnar with posterior triceps. recurrent artery. e) Nutrient: to the humerus in the spiral groove. 3) Inferior ulnar collateral artery:divided into two branches: a) Anterior branch: anastomoses with anterior ulnar recurrent artery. Branches: 1) Profunda brachii artery (largest branch): - It arises from brachial artery just below the lower border of teres major. - It accompanies the radial nerve. in the spiral groove till lateral side of the arm where it gives the following branches: a) Ascending branch (deltoid branch): - It anastomoses with descending branch of posterior circumflex humeral artery. b) Anterior descending branch (radial collateral): - It pierces the lateral intermuscular septum, accompanied with the radial nerve. - It ends in front of the lateral epicondyle by anastomosing with radial recurrent artery. c) Posterior descending branch (middle collateral): 2) Superior ulnar collateral artery: - Arises at middle of the arm, opposite insertion of coracobrachialis. - It pierces the medial intermuscular septum to reach back of medial epicondyle. It anastomoses with posterior ulnar recurrent artery. 3) Inferior ulnar collateral artery: - It arises two inches above the elbow. - It divides into two branches: a) Anterior branch: descends in front of medial epicondyle, and anastomoses with anterior ulnar recurrent artery. b) Posterior branch: pierces the medial intermuscular septum to reach the back of medial epicondyle and 1) Profunda brachii artery a) Ascending branch (deltoid branch): - It anastomoses with descending branch of posterior circumflex humeral artery. b) Anterior descending branch (radial collateral): - anastomosing with radial recurrent artery. c) Posterior descending branch (middle collateral): anastomose with interosseous recurrent artery. d) Muscular branches: to triceps. e) Nutrient: to the humerus in the spiral groove. 2) Superior ulnar collateral artery: It anastomoses with posterior ulnar recurrent artery. 3) Inferior ulnar collateral artery: a) Anterior branch: anastomoses with anterior ulnar recurrent artery. b) Posterior branch: anastomoses with posterior ulnarrecurrent artery 4) Nutrient artery: to the humerus Surface Anatomy: Draw a line between two points: -Point (1) on the posterior fold of axilla where the pulsations of the axillary artery can be felt. - Point (2) in cubital fossa medial to the tendon of biceps (midway between the 2 epicondyles).  AXILLARY NERVE COURSE AND RELATIONS: It arises from the posterior cord of the brachial plexus (C. 5, 6) behind the 3rd part of the axillary artery. It passes over the subscapularis and then curves backwards below it to enter the quadrangular space. In the quadrangular space, it is accompanied by the posterior I circumflex humeral vessels and both structures come in contact with the surgical neck of the humerus. The nerve winds laterally round the surgical neck immediately below the shoulder joint to come under cover of the deltoid muscle, where I it divides into anterior and posterior divisions. BRANCHES: 1. Articular branch: arises from the trunk of the nerve and ascends to supply the shoulder joint 2. Posterior division: passes along the posterior border of the deltoid and ends as the upper lateral cutaneous nerve of the arm. It gives off the following branches: - Branches to the deltoid. -Branch to the teres minor. -Upper lateral cutaneous nerve of the arm: supplies the skin of the upper part of the lateral side of the arm (over the lower 1/2 of the deltoid). 3. Anterior division: runs anteriorly in front of the surgical neck and ends in the deltoid. EFFECT OF INJURY: The axillary nerve is exposed to injury in:-Fracture of surgical neck of the humerus. -Downward dislocation of the head of the humerus. -Compression by an axillary crutch. Injury of the nerve leads to: Paralysis of the deltoid and teres minor: results in -failure of abduction of the arm from 15° to 90°. There is also flattening of the rounded contour of the shoulder due to loss of tone in the deltoid. -Affection of external rotation Loss of cutaneous sensation: over the lower 1/2 of deltoid (the skin over the upper 1/2 of deltoid is supplied by the lateral supraclavicular nerve from the cervical plexus). SUPRASCAPULAR NERVE COURSE AND RELATIONS: It arises from the upper trunk of the brachial plexus in the neck (C. 5. 6). It runs downwards and laterally to reach the upper border of the scapula in company with the suprascapular artery. The nerve passes deep to the suprascapular ligament, while the suprascapular vessels pass superficial to the ligament. * The nerve enters the supraspinous fossa and then passes through the spinoglenoid notch to reach the infraspinous fossa. DISTRIBUTION: It supplies the following: Supraspinatus muscle. Infraspinatus muscle. Shoulder and acromio-clavicular joints. PRASCAPULAR NERVE INJURY A suprascapular nerve injury presents as a vague shoulder pain with associated weakness in shoulder abduction and external rotation The suprascapular nerve supplies both the supraspinatus and infraspinatus muscles. When this nerve is compromised, there is significant atrophy of the supraspinatus and infraspinatus muscles, and the superior scapular fossa appears hollow SUPRASCAPULAR ARTERY COURSE AND RELATIONS: It is a branch of the thyro-cervical trunk of the 1st part of subclavian artery. It runs in the side of the neck behind the clavicle in company with the suprascapular nerve to reach the scapula. (It may rarely arise from the 3rd part of the subclavian artery.) It passes superficial to the suprascapular ligament and enters the supraspinous fossa. It continues through the spinoglenoid notch to enter the infraspinous fossa. It Joins the anastomosis around the scapula and gives branches to the shoulder joint, and to both the clavicle and scapula. BRANCHES: It gives branches to the anastomosis around the scapula. Acromial branch : anastomoses with the acromial branch of the thoraco-acromial artery. Nutrient branches: to the clavicle and scapula. Articular branches : to the shoulder and acromio- clavicular joints.