Anatomy - Arm and Cubital Fossa

The trochlea of the humerus articulates with

ulna

Capitellum of humerus articulates with

Radius

Medial epicondyle of humerus is an attachment site for

Muscles in anterior compartment of forearm

Lateral epicondyle of humerus is an attachment site for

Muscles of the posterior compartment of forearm

The interosseous membrane is

Fibrous membrane that exists between the radius and ulna

Fascia of the arm

Surrounds muscles and separates them into compartments

What is aponeurosis

Thickening of fascia

The anterior compartment of the arm contains which kinds of muscles

Flexors

The posterior compartment of the arm contains which kinds of muscles

Extensors

All forearm/elbow flexors are supplied by

Musculocutaneous nerve

How many times stronger are the forearm flexors than extensors

About twice

Brachialis also takes innervation from

Radial nerve, C7

The biceps brachii crosses how many joints

3 (GHJ, elbow, radioulnar)

How does the biceps brachii assist the rotator cuff muscles

It helps to depress the humeral head

In a forearm pronated position, the biceps brachii

Does not contribute to flexion of the forearm, most powerful supinator

In a semi pronated position, the biceps brachii

Only activates against resistance

Course of tendon of long head of biceps

Sits between insertion of pec major and teres major superficial to insertion of lats

The long head biceps tendon is supported by

Transverse humeral ligament

Tendon kinks can lead to an increase in

Load on a tendon

If a tendon were to completely rupture, strength of shoulder abduction decreases by

Approximately 20%

Where does the brachialis lie in relation to the biceps

Deep

Why is the brachialis the "workhorse" of the elbow

It always contracts to flex the forearm, and produces the greatest amount of flexion

The musculocutaneous nerve pierces the

Coracobrachialis

The Shunt muscles include

Coracobrachialis, short head of the biceps, long head of triceps

As a shunt muscle, the coracobrachialis

Helps resist downward dislocation of the head of humerus

The coracobrachialis might compress which structures that run deep to it

Median nerve and brachial artery

All muscles of the posterior compartment of the arm are innervated by

Radial nerve

The medial head of the triceps is akin to the

Brachialis, "workhorse" of forearm extension

The lateral head of the triceps is akin to the

Biceps long head, strongest

As a shunt muscle, the triceps long head

Helps to resist inferior displacement of head of humerus

The long head triceps aids in

Extension and adduction of the arm

How does the anconeus prevent pinching of the elbow joint in extension

It tenses the capsule

What is the function of collateral arteries

They continue to deliver blood when the main artery becomes occluded (blocked)

The brachial artery is a continuation of

Axillary artery

What branches come off of the brachial artery

- Profunda brachial artery

- Humeral nutrient artery

- Superior ulnar collateral artery

- Inferior ulnar collateral artery

The profunda brachial artery branches into

Radial collateral artery and middle collateral artery

The brachial artery branches into

Radial and ulnar artery under bicipital aponeurosis

Pulsation of the brachial artery is possible in the

Medial arm

Musculocutaneous nerve function in arm vs forearm

In the arm it innervates motor function, in the forearm it is sensory

Superficial veins of the arm supply

Skin

Deep veins accompany

Arteries

Course of the musculocutaneous nerve

- Exits lateral cord at lateral border of pec minor

- extends through the anterior axilla

- pierces the coracobrachialis

- runs between the biceps and brachialis

The musculocutaneous nerve branches

At the musculotendinous transition of the biceps muscle (elbow) it becomes the lateral cutaneous nerve

The lateral cutaneous nerve supplies to

Radial side of the forearm

Radial nerve course

- Extends from the posterior cord

- Travels towards posterior side of the arm in the radial groove

- Runs distally between the long and medial heads of the triceps (travels with profunda brachial artery)

- Pierces lateral intermuscular septum at lateral border of humerus

- Continues inferior between brachialis and brachioradialis

The radial nerve branches into

Posterior cutaneous nerve of arm/forearm

Posterior cutaneous nerve of arm/forearm supply to

Skin of the posterior upper arm forearm

What 5 nerves pass through the arm to the forearm

- Median

- Ulnar

- Radial

- Musculocutaneous (lateral cutaneous)

- Medial cutaneous n of forearm

Anterior to the lateral epicondyle, the radial nerve divides into

Superficial and deep branches

Median nerve course

- Emerges from medial and lateral cords and runs anterior to axillary artery

- Runs distal in arm lateral to brachial artery

- Descends into the cubital fossa deep to the bicipital aponeurosis and median cubital vein

The median cubital vein is a joining of

Cephalic and basilic veins

The median nerve supplies what in the elbow joing

Articular branches

Ulnar nerve course

- Passes anterior to the insertion of the teres major and long head of the triceps and medial to the brachial artery

- Passes posterior to the medial epicondyle and medial to the olecranon

- Enters the forearm posterior to the medial epicondyle (funny bone)

Axillary nerve supplies sensation to the

Lateral shoulder region

Which nerves do not supply musculature or skin on the arm

Median and Ulnar

Articulation of the elbow joint includes the

- Humero-ulnar

- Humero-radial

- Proximal radioulnar

The Proximal radioulnar joint is involved in what motion

Pronation and supination

The proximal radioulnar joint is what type of joint

Pivot

The humeroulnar joint is what type of joint

Hinge

The humeroulnar and humeroradial joint allows for what motion

Forearm (elbow) flexion

The humeroradial joint is what type of joint

Hinge and pivot

Why is the elbow joint capsule weaker anterior/posterior

The elbow flexes a lot

Why is the elbow joint stronger mediolaterally

Less motion in those directions

The synovial membrane in the elbow lines the

internal surface of the capsule and the intracapsular non-articular parts of the humerus

The synovial membrane is separated by

Pads of fat in regions that overly the fossa

The function of fat pads in the elbow joint is to

Accommodate the bony processes during extension and flexion of the elbow

The collateral ligaments of the elbow joint includes the

Radial (lateral) collateral ligament and ulnar (medial) collateral ligament

The radial collateral ligament complex extends from

Lateral epicondyle to the lateral part of the annular ligament

The ulnar collateral ligament extends from

Medial epicondyle of the humerus to the olecranon + coranoid of the ulna

The three bands of the ulnar collateral ligament includes

- Anterior, cord-like

- Posterior, fan-like

- Oblique/transverse

The anterior cord of the ulnar collateral ligament

Is the strongest and provides stability through range

The posterior band of the ulnar collateral ligament

Is the weakest and stabilizes in flexion

The oblique band of the ulnar collateral ligament

Deepens the socket for the trochlea and humerus but does not provide stability

The radial collateral ligament prevents

Excessive varus force in the elbow joint

The ulnar collateral ligament prevents

Excessive valgus force at the elbow joint

The annular ligament is located

At the radius, it encircles and holds the head in the radial notch of ulna

The annular ligament permits what motions of the forearm

Pronation and supination

The annular ligament holds the

Head of the radius against the capitellum

What is the carrying angle

The angle away from the body that is created when the forearm is supinated next to the body

What are the borders of the cubital fossa

- Superiorly, an imaginary line between medial and lateral epicondyles

- Medially, pronator teres

- Laterally, brachioradialis

The major contents of the cubital fossa from lateral to medial includes

-Radial nerve

-Tendon of biceps brachii muscle

- Brachial artery (terminal part)

- Median nerve

The medial cubital vein located in the overlying skin connects the

Cephalic vein and basilic

In the absence of resistance, which muscles help to flex the forearm

Brachioradialis and pronator teres

Where would intratendinous olecranon bursa sometimes be found

Tendon of triceps brachii

Where would subtendinous olecranon bursa be located

Between the olecranon and the triceps tendon just proximal to its attachment to the olecranon

Where would subcutaneous olecranon bursa be located

Subcutaneous connective tissue over the olecranon

Why is "Nursemaid's elbow" (dislocation of radius) common in children

The ossification of the UE is not yet complete, so there is a lot less stability in the elbow joints

Medial (ulnar) collateral ligament injury is caused by

Valgus stress, usually during throwing

Joint pain in children is usually due to

Growth plates