80 Questions
What is the primary function of the extensor digitorum?
Extension of the proximal phalanges
What happens to the retinacular ligament during flexion of the distal interphalangeal joint?
It becomes taut and pulls the proximal joint into flexion
What is the primary attachment point of the extensor digiti minimi tendon?
Dorsal digital expansion of the little finger
What is the function of the collateral reinforcements of the extensor digitorum?
To extend the middle and distal phalanges
What is the role of the retinacular ligament in extending the proximal joint?
It pulls the proximal joint into flexion
What is the purpose of pronating the forearm when testing the extensor digitorum?
To isolate the extensor digitorum
What is the direction of the retinacular ligament?
Obliquely across the middle phalanx and two interphalangeal joints
What is the secondary function of the extensor digitorum?
To extend the middle and distal phalanges
What is the orientation of the median nerve in relation to the brachial artery as it passes inferolaterally?
It crosses anterior to the artery
Which of the following arteries is NOT a branch of the brachial artery?
Radial artery
Where does the ulnar nerve pierce to enter the posterior compartment?
Medial intermuscular septum
What is the function of the collateral arteries in the elbow region?
To form the peri-articular arterial anastomoses
What is the course of the profunda brachii artery in relation to the humerus?
It passes posteriorly around the shaft of the humerus
What is the name of the artery that arises from the lateral aspect of the brachial artery?
Humeral nutrient artery
What is the termination of the profunda brachii artery?
It terminates by dividing into the middle and radial collateral arteries
What is the relationship between the recurrent branches of the radial, ulnar, and interosseous arteries and the elbow joint?
They run superiorly anterior and posterior to the elbow joint
What is the function of the tubercle in relation to the extensor pollicis longus?
To act as a pulley to change the line of pull
What is the anatomical snuff box bounded by?
The tendons of the APL and EPB anteriorly, and the tendon of the EPL posteriorly
What is the action of the extensor indicis on the index finger?
It confers independence to the index finger
Where do the ulnar and radial arteries usually arise from?
The brachial artery in the cubital fossa
What is the location of the radial artery in relation to the anatomical snuff box?
It lies in the floor of the snuff box
What is the action of the extensor pollicis longus on the thumb?
It adducts the thumb and rotates it laterally
What can be palpated proximally in the anatomical snuff box?
The radial styloid process
What can be felt in the floor of the anatomical snuff box?
The scaphoid and trapezium bones
Why do the muscles that operate the distal forearm, wrist, and hand have their bulky, fleshy, contractile parts located proximally in the forearm?
To minimize bulk and maximize functionality
What is the function of the long, slender tendons extending from the muscles to the operative site?
To transmit force from the muscle to the site of action
Why do the muscles of the forearm have long contractile parts?
Because the structures on which they act have an extensive range of motion
What is the purpose of the medial and lateral extensions of the distal humerus?
To provide the required attachment sites for the flexors and extensors of the wrist and fingers
Why do the flexors and extensors of the wrist and fingers have their proximal attachments in the arm?
Because the forearm is not long enough to provide the required length
What is the relationship between the flexors and extensors of the elbow and the aspects of the distal humerus?
The flexors and extensors occupy the anterior and posterior aspects of the humerus
In the proximal forearm, what is the actual location of the 'anterior' flexor–pronator compartment?
Anteromedially
What is the relationship between the 'posterior' extensor–supinator compartment and the aspects of the proximal forearm?
It lies posterolaterally
What is the structure that anchors the extensor retinaculum to the radius and ulna?
Fascia on the posterior aspect of the distal-most forearm
What are the three outcropping muscles of the thumb that emerge from between the extensor carpi radialis brevis and extensor digitorum?
Abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus
What is the nerve that supplies the muscles in the posterior compartment of the forearm?
Radial nerve
What is the structure that the four flat tendons of the extensor digitorum pass deep to?
Extensor retinaculum
What are the names of the two muscles in the superficial group that are attached proximally to the lateral supra-epicondylar ridge of the humerus and adjacent lateral intermuscular septum?
Brachioradialis and extensor carpi radialis longus
What is the name of the muscle that has been exposed by opening the furrow proximally to the lateral epicondyle?
Supinator muscle
What is the common attachment of the four superficial extensors (extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris)?
Lateral epicondyle
What is the structure that the tendons of the extensor indicis and extensor digiti minimi join on their medial sides near the knuckles?
Common tendons of the index and little fingers
The pectoralis major and minor muscles are reflected inferolaterally.
False
The musculocutaneous nerve arises from a segment of the posterior cord.
False
The posterior cord gives rise to six peripheral nerves.
False
The biceps brachii has three heads.
False
The triceps is particularly important for wheelchair activity.
True
The pectoralis major and minor muscles are reflected medially.
False
The brachialis is innervated by a branch of the radial nerve.
True
The biceps brachii has one head.
False
The brachial artery lies posterior to the triceps and brachialis throughout its course.
False
The radial nerve and accompanying profunda brachii artery wind anteriorly around the humerus.
False
The radial and ulnar arteries arise from the lateral aspect of the brachial artery.
False
The brachial artery is relatively deep and not palpable throughout its course.
False
The radial nerve divides into a superficial (motor) and a deep (sensory) branch.
False
The cubital fossa is opened widely by retracting the flexor muscles laterally and the extensor muscles medially.
False
The brachial artery passes posterior to the medial supra-epicondylar ridge and trochlea of the humerus.
False
The radial nerve pierces the medial intermuscular septum to enter the anterior compartment.
False
The interosseous membrane is thin and weak.
False
The head of the radius is at the distal end of the forearm.
False
The forearm bones are not joined by an interosseous membrane.
False
The forearm movement occurs at the wrist and radio-ulnar joints.
False
The ulnar artery emerges from its oblique course posterior to the flexor digitorum profundus.
False
The muscles of similar purpose and innervation are not grouped within the same fascial compartments in the forearm.
False
The proximal boundary of the forearm is defined by the joint plane of the wrist.
False
The distal humerus is not functionally part of the forearm.
False
The head of the humerus is surrounded by muscles on all sides.
False
The medial and lateral epicondyles of the humerus are not subcutaneous.
False
The brachial artery is palpable superior to the medial border of the biceps.
False
The arm forms a column with the radius at its center.
False
The median cubital vein crosses the bicipital aponeurosis as it runs inferomedially connecting the cephalic to the basilic vein.
False
The muscular masses of the long flexors of the forearm form the lateral border of the cubital fossa.
False
The lateral group of forearm extensors is a hard mass that cannot be grasped separately.
False
The cephalic and basilic veins in the subcutaneous tissue are not visible when a tourniquet is applied to the arm.
False
The distal forearm, wrist, and hand are operated by intrinsic muscles having their bulky, fleshy, contractile parts located distally in the forearm.
False
The long, slender tendons extend proximally to the operative site.
False
The proximal attachments of the muscles must occur distal to the elbow—in the forearm.
False
The flexors and extensors of the elbow occupy the posterior and anterior aspects of the distal humerus, respectively.
False
The 'anterior' flexor–pronator compartment lies posterolaterally in the proximal forearm.
False
The 'posterior' extensor–supinator compartment lies anteromedially in the proximal forearm.
False
The medial and lateral extensions of the distal humerus provide proximal attachment sites for the flexors and extensors of the elbow.
False
The muscles that operate the distal forearm, wrist, and hand have their bulky, fleshy, contractile parts located in the hand.
False
Study Notes
Course of Nerves and Arteries in the Arm
- The ulnar nerve pierces the medial intermuscular septum to enter the posterior compartment and lies in the groove for the ulnar nerve on the posterior aspect of the medial epicondyle of the humerus.
- The median nerve and brachial artery descend in the arm to the medial side of the cubital fossa, where they are well protected and rarely injured.
- The brachial artery gives rise to many unnamed muscular branches and the humeral nutrient artery during its course through the arm.
- The main named branches of the brachial artery arising from its medial aspect are the profunda brachii artery and the superior and inferior ulnar collateral arteries.
Profunda Brachii Artery
- The profunda brachii artery is the largest branch of the brachial artery and has the most superior origin.
- It accompanies the radial nerve along the radial groove as it passes posteriorly around the shaft of the humerus.
- The profunda brachii terminates by dividing into middle and radial collateral arteries, which participate in the peri-articular arterial anastomoses around the elbow.
Forearm and Wrist
- The forearm, wrist, and hand are operated by "remote control" by extrinsic muscles having their bulky, fleshy, contractile parts located proximally in the forearm, distant from the site of action.
- The proximal attachments (origins) of the muscles must occur proximal to the elbow—in the arm—and are provided by the humerus.
- The medial and lateral extensions (epicondyles and supra-epicondylar ridges) of the distal humerus have developed to provide the required attachment sites for the flexors and extensors of the wrist and fingers.
Forearm Muscles
- Flexors lie anteriorly and extensors posteriorly in the forearm.
- The "anterior" flexor-pronator compartment actually lies anteromedially, and the "posterior" extensor-supinator compartment lies posterolaterally in the proximal forearm.
- The distal extensor tendons have been removed from the dorsum of the hand without disturbing the arteries because they lie on the skeletal plane.
Extensor Muscles of the Forearm
- The four flat tendons of the extensor digitorum pass deep to the extensor retinaculum to the medial four fingers.
- The common tendons of the index and little fingers are joined on their medial sides near the knuckles by the respective tendons of the extensor indicis and extensor digiti minimi.
Extensor Digitorum
- The extensor digitorum acts primarily to extend the proximal phalanges, and through its collateral reinforcements, it secondarily extends the middle and distal phalanges as well.
- It helps extend the hand at the wrist joint.
Extensor Digiti Minimi
- The extensor digiti minimi is a partially detached part of the extensor digitorum.
- The tendon of this extensor of the little finger runs through a separate compartment of the extensor retinaculum, posterior to the distal radio-ulnar joint, within the tendinous sheath of the extensor digiti minimi.
Extensor Pollicis Longus
- The extensor pollicis longus uses the tubercle as a trochlea (pulley) to change its line of pull as it proceeds to the base of the distal phalanx of the thumb.
- It adducts the extended thumb and rotates it laterally.
Arteries of Forearm
- The main arteries of the forearm are the ulnar and radial arteries, which usually arise opposite the neck of the radius in the inferior part of the cubital fossa as terminal branches of the brachial artery.
The Importance of Extensors in the Elbow
- Extensors of the elbow are crucial for raising oneself out of a chair and for wheelchair activity, making conditioning of the triceps particularly important in elderly or disabled persons.
Nerves and Muscles of the Arm
- The posterior cord of the brachial plexus gives rise to five peripheral nerves, four of which supply the muscles of the posterior wall of the axilla and posterior compartments of the upper limb.
- The muscles of the arm, including the biceps brachii, have attachments, innervation, and actions that are described in Table 3.9.
Biceps Brachii
- The biceps brachii muscle has two heads that begin at the inferior border of the teres major and end in the cubital fossa opposite the neck of the radius.
- The muscle divides into the radial and ulnar arteries under cover of the bicipital aponeurosis.
Arterial Supply of the Arm and Forearm
- The radial nerve and accompanying profunda brachii artery wind posteriorly around the humerus in the radial groove.
- The brachial artery lies anterior to the triceps and brachialis, and its pulsations are palpable in the medial bicipital groove.
Cubital Fossa
- The cubital fossa is a triangular region bounded by the brachialis and brachioradialis, and contains the radial nerve, which divides into superficial and deep branches.
- The brachial artery lies anterior to the triceps and brachialis in the cubital fossa.
Forearm and Wrist
- The forearm extends from the elbow to the wrist and contains two bones, the radius and ulna, which are joined by an interosseous membrane.
- The forearm is divided into anterior and posterior compartments, with flexors and extensors of the wrist and fingers located in the anterior and posterior compartments, respectively.
Compartments of the Forearm
- The forearm has compartments of flexors and extensors, which are grouped according to their purpose and innervation.
- The forearm flexors are located anteromedially, while the extensors are located posterolaterally.
Quiz on the anatomical structure of the arm, including the ulnar nerve, median nerve, and brachial artery.
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