The ArmThe Arm

Maribel G. Castro-Enano, MDMaribel G. Castro-Enano, MD

CPU College of MedicineCPU College of Medicine

A. HumerusA. Humerus- a long bone which has a cylindrical shaft which - a long bone which has a cylindrical shaft which

flattens anteroposteriorly downwards flattens anteroposteriorly downwards

- distal end has articular and non-articular parts- distal end has articular and non-articular parts

Articular part:Articular part:1. Capitulum – for the head of the radius1. Capitulum – for the head of the radius

2. Trochlea – for the trochlear notch of the ulna2. Trochlea – for the trochlear notch of the ulna

- 2 projections at the distal end- 2 projections at the distal end1. medial epicondyle1. medial epicondyle

2. lateral epicondyle2. lateral epicondyle

- 3 fossae- 3 fossae1. radial fossa anterior1. radial fossa anterior

2. coronoid fossa2. coronoid fossa

3. olecranon fossa – posterior; receives the olecranon of 3. olecranon fossa – posterior; receives the olecranon of the ulna when the elbow is extendedthe ulna when the elbow is extended

A. HumerusA. Humerus- lower half of the body is flattened and is divided - lower half of the body is flattened and is divided

by the medial and lateral supracondylar ridges by the medial and lateral supracondylar ridges into into anterior and posterior surfacesanterior and posterior surfaces for the for the brachialis and medial head of the tricepsbrachialis and medial head of the triceps

- supracondylar ridges- supracondylar ridges give attachment to the give attachment to the intermuscular septa for additional attachment of intermuscular septa for additional attachment of musclesmuscles

- the lateral ridge ascends to a broad shallow - the lateral ridge ascends to a broad shallow groove, the groove, the spiral groove spiral groove (radial nerve)(radial nerve)

B. MusclesB. Muscles

- muscles are muscles are enveloped in a sleeve enveloped in a sleeve of tough deep fasciaof tough deep fascia

- sleeve divided into an sleeve divided into an anterior and a anterior and a posterior posterior compartment by the compartment by the medial and lateral medial and lateral intermuscular septaintermuscular septa

B. MusclesB. Muscles

1. Anterior Compartment1. Anterior Compartment

a. corachobrachialis a. corachobrachialis – – shares a common tendon from the tip of the coracoid shares a common tendon from the tip of the coracoid process with the process with the short head of the biceps short head of the biceps

- - important mainly as a landmark (e.g. musculocutaneous important mainly as a landmark (e.g. musculocutaneous nerve pierces it)nerve pierces it)

- origin: tip of coracoid process- origin: tip of coracoid process

- insertion: medial surface of humerus- insertion: medial surface of humerus

- action: helps to flex and adduct arm- action: helps to flex and adduct arm

1. Anterior Compartment cont…..1. Anterior Compartment cont…..

b. bicepsb. biceps- has 2 heads- has 2 heads

1.) long head – descends in the intertubercular 1.) long head – descends in the intertubercular sulcus encased in a synovial sheath continuous with the sulcus encased in a synovial sheath continuous with the synovial cavity of the shoulder jointsynovial cavity of the shoulder joint

- origin: supraglenoid tubercle of the - origin: supraglenoid tubercle of the scapulascapula

2.) short head – origin: tip of coracoid process of 2.) short head – origin: tip of coracoid process of scapulascapula

- insertion: tuberosity of radius and bicipital aponeurosis- insertion: tuberosity of radius and bicipital aponeurosis

- action: supinates forearm and, when it is supine, flexes - action: supinates forearm and, when it is supine, flexes forearmforearm

c. brachialisc. brachialis

- origin: distal half of anterior surface of - origin: distal half of anterior surface of humerus and intermuscular septahumerus and intermuscular septa

- insertion: coronoid process and tuberosity - insertion: coronoid process and tuberosity of ulnaof ulna

- action: flexes forearm in all positions- action: flexes forearm in all positions

2. Posterior Compartment2. Posterior Compartment

a. triceps brachii a. triceps brachii - has 3 heads- has 3 heads

1.) long head – from infraglenoid tubercle of scapula1.) long head – from infraglenoid tubercle of scapula

2.) lateral head – from posterior surface of humerus, 2.) lateral head – from posterior surface of humerus, superior to the radial groovesuperior to the radial groove

3.) medial head – from posterior surface of humerus 3.) medial head – from posterior surface of humerus below the level of the spiral groovebelow the level of the spiral groove

- insertion: olecranon process of ulna- insertion: olecranon process of ulna

- action: - action: chief extensor of the forearmchief extensor of the forearm

keep the elbow extended when pushing an keep the elbow extended when pushing an objectobject

long head steadies head of abducted long head steadies head of abducted humerushumerus

*b. aconeus*b. aconeus

- appears like an extension of the triceps- appears like an extension of the triceps

- should be considered as part of the medial - should be considered as part of the medial head of the triceps head of the triceps

- origin: lateral epicondyle of humerus- origin: lateral epicondyle of humerus

- insertion: lateral surface of olecranon and - insertion: lateral surface of olecranon and superior part of posterior surface of ulnasuperior part of posterior surface of ulna

- action: assists triceps in extending forearm- action: assists triceps in extending forearm

stabilizes elbow jointstabilizes elbow joint

abducts ulna during pronationabducts ulna during pronation

C. NERVESC. NERVES1. Musculocutaneous n.1. Musculocutaneous n.

- arises from the lateral cord of the brachial plexus (C5,6,7)- arises from the lateral cord of the brachial plexus (C5,6,7)

- pierces the corachobrachialis and continues between the - pierces the corachobrachialis and continues between the biceps and brachialisbiceps and brachialis

- at the lateral border of the tendon of the biceps it - at the lateral border of the tendon of the biceps it emerges as the emerges as the lateral cutaneous nerve of the forearmlateral cutaneous nerve of the forearm

2. Ulnar n.2. Ulnar n.- arises from the medial cord (C7,8,T1)- arises from the medial cord (C7,8,T1)

- without any branching extends to the posterior surface of - without any branching extends to the posterior surface of the medial epicondyle and onward into the forearmthe medial epicondyle and onward into the forearm

- in the elbow region, it is accompanied by the superior - in the elbow region, it is accompanied by the superior ulnar collateral artery and the ulnar collateral artery and the ulnar collateral nerveulnar collateral nerve, sent , sent by the radial nerve to the medial head of the tricepsby the radial nerve to the medial head of the triceps

3. Median n.3. Median n.- the 2 roots unite in the axilla on the lateral side of the - the 2 roots unite in the axilla on the lateral side of the arteryartery

- slowly slips across the brachial artery, lying medial to it at - slowly slips across the brachial artery, lying medial to it at the elbowthe elbow

- no branches in the axilla or the arm- no branches in the axilla or the arm

- commonly receives a large communication from the - commonly receives a large communication from the musculocutaneous n. and occasionally gives one to itmusculocutaneous n. and occasionally gives one to it

4. Radial n.4. Radial n.- “continuation” of the posterior cord (C5,6,7,8 (T1))- “continuation” of the posterior cord (C5,6,7,8 (T1))

- largest branch of the brachial plexus- largest branch of the brachial plexus

- lies posterior to the axillary artery and then the brachial - lies posterior to the axillary artery and then the brachial artery anterior to the long head of the tricepsartery anterior to the long head of the triceps

- passes inferolaterally with the profunda brahii artery - passes inferolaterally with the profunda brahii artery around the body of the humerus in the around the body of the humerus in the radial grooveradial groove

4. Radial n. cont…..4. Radial n. cont…..

- as it reaches the lateral border of the humerus, it pierces - as it reaches the lateral border of the humerus, it pierces the lateral intermuscular septum between the brachialis the lateral intermuscular septum between the brachialis and brachioradialis lateral epicondyle divides into and brachioradialis lateral epicondyle divides into deep and superficial branchesdeep and superficial branches

a. a. superficial radial nervesuperficial radial nerve – sensory branch to the – sensory branch to the dorsum of the hand and digitsdorsum of the hand and digits

b. b. posterior interosseous nerve posterior interosseous nerve (deep radial nerve)(deep radial nerve)

- entirely motor - entirely motor

- disappears into the substance of the supinator - disappears into the substance of the supinator just below the elbowjust below the elbow

- at the lateral side of the arm and at the elbow, branches - at the lateral side of the arm and at the elbow, branches pass from the radial and posterior interosseous nerves to pass from the radial and posterior interosseous nerves to

a. brachioradialisa. brachioradialis

b. extensor carpi radialis longusb. extensor carpi radialis longus

c. extensor carpi radialis brevisc. extensor carpi radialis brevis

d. supinatord. supinator

D. BLOOD VESSELSD. BLOOD VESSELS1. Brachial Artery1. Brachial Artery

- arises from the axillary artery- arises from the axillary artery

- pulsations and walls can be felt readily- pulsations and walls can be felt readily

- divides into its 2 terminal branches at the level - divides into its 2 terminal branches at the level of the neck of the radius, 2-3 cm distal to the of the neck of the radius, 2-3 cm distal to the crease of the elbowcrease of the elbow

a. ulnar arterya. ulnar artery

b. radial artery – smallerb. radial artery – smaller

Collateral Branches of the Brachial Collateral Branches of the Brachial ArteryArtery

1. Profunda brachii a.1. Profunda brachii a.-- largest and most superior branch largest and most superior branch

- accompanies the radial nerve in the radial groove- accompanies the radial nerve in the radial groove

- posterior to the humerus, divides into anterior and - posterior to the humerus, divides into anterior and posterior descending branches which help to form the posterior descending branches which help to form the arterial anastomoses of the elbow regionarterial anastomoses of the elbow region

2. Superior ulnar collateral a.2. Superior ulnar collateral a.- arises from brachial a. near the middle of the arm- arises from brachial a. near the middle of the arm

- accompanies the ulnar n. posterior to the medial - accompanies the ulnar n. posterior to the medial epicondyleepicondyle

- anastomoses with the posterior ulnar recurrent branch - anastomoses with the posterior ulnar recurrent branch of the ulnar artery and the inferior ulnar collateral a.of the ulnar artery and the inferior ulnar collateral a.

3. Inferior ulnar collateral a.3. Inferior ulnar collateral a.- arises from the brachial a. about 5 cm proximal to the elbow - arises from the brachial a. about 5 cm proximal to the elbow creasecrease

- passes inferomedially anterior to the medial epicondyle , - passes inferomedially anterior to the medial epicondyle , where it joins the anastomoses of the elbow regionwhere it joins the anastomoses of the elbow region

4. Nutrient humeral a.4. Nutrient humeral a.- arises from the brachial artery around the middle of the arm- arises from the brachial artery around the middle of the arm

- enters the nutrient canal on the anteromedial surface of the - enters the nutrient canal on the anteromedial surface of the humerushumerus

5. Muscular branches5. Muscular branches

The brachial artery and its collaterals

VEINSVEINS1. Venae comitantes – accompany the brachial artery and 1. Venae comitantes – accompany the brachial artery and

make a very open network around itmake a very open network around it

2. Cephalic vein – located in the superficial fascia along the 2. Cephalic vein – located in the superficial fascia along the anterolateral surface of the biceps and is often visible anterolateral surface of the biceps and is often visible through the skinthrough the skin

3. Basilic vein – also located in the superficial fascia and 3. Basilic vein – also located in the superficial fascia and passes on the medial side of the inferior part of the armpasses on the medial side of the inferior part of the arm

- near the middle and inferior 3- near the middle and inferior 3rdrd of the of the arm, it passes deep to the brachial fascia and runs arm, it passes deep to the brachial fascia and runs superiorly to the axillasuperiorly to the axilla

4. Medial cubital vein – forms the communication between the 4. Medial cubital vein – forms the communication between the basilic and cephalic veins in the cubital fossabasilic and cephalic veins in the cubital fossa

- lies anterior to the bicipital - lies anterior to the bicipital aponeurosisaponeurosis

Good Afternoon!Good Afternoon!