Muscles Of The Forearm And Carpal Tunnel Flashcards
How many muscles are in the anterior compartment of the forearm
8
How are the muscles arranged in the anterior compartment of the forearm
3 layers: superficial, middle and deep
Number of muscles in superficial layer of the anterior compartment of the forearm
4
Muscles in superficial layer of the anterior compartment of the forearm from lateral to medial
Pronator teres
Flexor carpi radialis
Palmaris longus
Flexor carpi ulnaris
What are the superficial muscles of the anterior compartment of the forearm attached to
Medial epicondyle of humerus
Pronator teres function
Pronator of proximal radioulnar joint
Flexor carpi radialis function
Flexes and abducts the wrist
Palmaris longus
Small muscle belly but a long thin easily recognisable tendon when present
Tendon inserts into the fascia of the palm of the hand
Flexor carpi ulnaris function
Flexes and adducts the wiret
Flexor carpi ulnaris innervation
Ulnar nerve
Pronator teres innervation
Median nerve
Flexor carpi radialis innervation
Median nerve
Palmaris longus innervation
Median nerve
Which muscle makes up the middle layer of the anterior compartment of the forearm
Flexor digitorium superficialis
Flexor digitorum superficialis
Gives rise to 4 tendons
Flexor of the digits
Flexor digitorum superficialis innervation
Median nerve
Path of median nerve in anterior compartment of the forearm
Travels between flexor digitorum superficialis and flexor digitorum profundus
Number of muscles in deep layer of anterior compartment of the forearm
3
Muscles in deep layer of anterior compartment of the forearm
Flexor digitorum profundus
Flexor pollicis longus
Pronator quadratus
Flexor pollicis longus function
Flexes the thumb
Flexor digitorum profundus function
Flexor of the digits
Gives rise to 4 tendons
Innervation of lateral half of flexor digitorum profundus
Median nerve
Index to middle finger
Innervation of medial half of the flexor digitorum profundus
Ulnar nerve
Ring and little fingers
Pronator quadratus
Deepest forearm muscle
Square-shaped
Located over the distal ends of the radius and ulnar
Function of Pronator quadratus
Pronates the distal radioulnar joint
All anterior forearm muscles are flexors except…
Pronator teres and Pronator quadratus
All anterior forearm muscles are innervated by the median nerve except…
Flexor carpi ulnaris and medial half of flexor digitorum profundus— ulnar nerve
Layers of muscles in the posterior compartment of the forearm
Superficial and deel
What are all muscles of the posterior compartment of the forearm innervated by
Radial nerve
Number of muscles in the superficial layer of the posterior compartment of the forearm
7
Muscles in the superficial layer of the posterior compartment of the forearm
Brachioradialis
Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor digitorum
Extensor digiti minimi
Extensor carpi ulnaris
Anconeus
What are the muscles of the superficial layer of the posterior compartment of the forearm attached to proximally
Lateral epicondyle of the humerus
Where is the common extensor origin
Lateral epicondyle of humerus
Where is the common flexor origin
Medial epicondyle of humerus
Extensor digiti minimi function
Extends the little finger via its insertion into the dorsum of the little finger
Extensor carpi ulnaris function
Most medial
Extends and adducts the wrist via insertion onto the 5th metacarpal
Extensor digitorum function
Extends the digits via 4 long tendons that insert into the dorsal aspects if the fingers
Connected by fibrous bands
Why is it difficult to fully extend the middle or ring fingers independently
Tendons of the extensor digitorum are connected by fibrous bands
What does the extensor carpi radialis longus insert into
2nd metacarpal
What does the extensor carpi radialis brevis insert into
3rd metacarpal
Function of the extensor carpi radialis longus and brevis
Extend and abduct the wrist
Brachioradialis location
On the boundary between the anterior and posterior compartments of the forearm
Originates at the humerus, proximal to the lateral epicondyle and inserts on the distal radius
Brachioradialis functions
Weak flexor of the elbow joint
Extensor retinaculum
A band of tissue which prevents the tendons from bowing when the wrist is extended
Anconeus location
Small muscle found proximally near the olecranon
Anconeus function
Very weak extensor of the elbow
Number of muscles in the deep layer of the posterior compartment of the forearm
5
Muscles in the deep layer of the posterior compartment of the forearm
Supinator
Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus
Extensor indicis
Supinator function
Supinates forearm
Supinator location
Attached proximally to humerus
Wraps around the proximal part of the radius
Abductor pollicis longus function
Abducts the thumb
Where does the abductor pollicis longus insert
1st metacarpal
Extensor pollicis longus and brevis function
Extend the thumb
Extensor indicis
Inserts on the dorsum of the index finger
Allows independent extension
Extensor pollicis brevis insertion
Proximal phalanx- so extends the metacarpophalangeal joint
Extensor pollicis longus inserts
Distal phalanx- so extends the interphalangeal joint of the thumb
Where do the tendons of the extensor pollicis brevis and longus lie
Superficially at the wrist as they wrap around the distal radius
All posterior forearm muscles are extensors except…
Brachioradialis
Supinator
Abductor pollicis longus
Except for the Supinator, where do all muscles of the deep layer of the posterior compartment of the forearm attach
Proximally to the forearm bones and interosseous membrane
Which arteries anastomose in the palm of the hand to form the palmar arches
Radial and ulnar
2 terminal branches of the brachial artery
Radial and ulnar artery
Path of radial artery
Lateral aspect of forearm
Path of ulnar artery
Medial aspect of forearm
Where can the radial artery be palpated
At the wrist by locating the tendon of the flexor carpi radialis at the level of the distal radius and palpating just lateral
Where can the ulnar artery be palpated
Not easily as deep to the flexor carpi ulnaris tendon
Carpal tunnel
A narrow passageway at the wrist
What forms the floor and sides of the carpal tunnel
Carpal bones
Flexor retinaculum
A fibrous band which forms the roof of the carpal tunnel
What forms the roof of the carpal tunnel
Flexor retinaculum
What does the flexor retinaculum attach to laterally
Scaphoid and trapezium
What does the flexor retinaculum attach to medially
Hook of the hamate and pisiform
Which tendons of the anterior forearm muscles travel through the carpal tunnel
Flexor digitorum superficialis (4)
Flexor digitorum profundus (4)
Flexor pollicis longus (1 to thumb)
What travels through the carpal tunnel
Median nerve
Tendons of anterior forearm muscles
Tendon of the FCR travels through the flexor retinaculum which forms the roof of the carpal tunnel
Carpal tunnel syndrome
The carpal tunnel is very narrow, so the tendons and median nerve are tightly packed into it. Any condition that further reduces space in the carpal tunnel, such as swelling of the tendons or arthritis between the joints of the carpal bones, will decrease the space and increase the pressure in the carpal tunnel. This can compress the median nerve and cause carpal tunnel syndrome (CTS). A patient with carpal tunnel syndrome typically presents with:
• impaired or altered sensation over the skin of the hand supplied by the median nerve. The patient may experience tingling, numbness, or pain in the hand.
• weakness of the hand muscles supplied by the median nerve – particularly the small muscles of the thumb.
It is important to recognise and treat CTS. If left untreated, the small muscles of the thumb may atrophy and weakness may be permanent, which has serious consequences for a patient. The flexor retinaculum is divided to alleviate the compression. The radial artery, ulnar artery and ulnar nerve do not travel through the carpal tunnel.
Injury to the flexor tendons
The flexor tendons are at risk from lacerations over the anterior forearm and wrist. In patients with such injuries, it is important to test the movements of the wrist and fingers to ascertain whether any tendons have been injured. Patients with confirmed or suspected tendon injuries require a surgical assessment. Failure to recognise tendon injuries may leave patients with permanent impairment.
Wrist drop
This describes an inability to extend the wrist (and fingers) due to weakness or paralysis of the posterior forearm muscles. It results from injury to the radial nerve proximal to the forearm. It is typically caused by a mid-shaft humeral fracture, as the radial nerve lies close to the bone here. Sensation is also impaired over the lateral aspect of the dorsum of the hand (i.e. in the regions of skin of the hand supplied by the radial nerve).
Lateral and medial epicondylitis
This is inflammation of the tendinous insertions of the superficial extensor muscles in the forearm at the lateral epicondyle, or the superficial flexor muscles in the forearm at the medial epicondyle. It tends to be caused by repetitive use and strain of the muscles, such as during a tennis serve for lateral epicondylitis (‘tennis elbow’), or a golf swing for medial epicondylitis (‘golfer’s elbow’). Pain is felt around the affected epicondyle and may radiate down the forearm.
Arterial blood gas sampling
The vast majority of blood tests require venous blood, which can be relatively easily taken from the superficial veins in the forearm and hand as discussed. However, to accurately assess a patient’s blood-oxygen and blood-carbon dioxide level, a sample of arterial blood is required. Most often, this is taken from the radial artery. As it a deep structure, clinicians must know the anatomy well to be able to use one hand to palpate the pulse and use the other to direct a needle into the radial artery to acquire the sample.
- Name the three major nerves that enter the forearm. What muscle compartments do they supply?
Radial- posterior
Median -anterior
Ulnar - some muscles in anterior (flexor carpi ulnaris and ulnar half of flexor digitorum profundus)
- Which nerve supplies the muscles in the posterior forearm? Which region of skin in the hand does this nerve also innervate?
Radial nerve
Skin over the dorsal surface of the lateral side of the hand and the dorsum of the lateral 3 1/2 digits as far as the DIP joitns
- Which muscles would be affected by an ulnar nerve injury in the mid-forearm?
Muscles distal to the mid forearm i.e. most of the small muscles of the hand (abductor pollicis, the hypothenar eminence muscles, the medial two lumbricals and all the interossei)
- Where is the common flexor origin? Which sport often causes inflammation of this joint?
Medial epicondyle of humerus
Golf
- How would you test the muscles of the forearm supplied by the median nerve?
Flexion of thumb and lateral 2 fingers
Movement of the thumb under the control of the thenar eminence muscle
- Where can the brachial, radial, and ulnar pulses be palpated? Which is easier to palpate, and why?
Brachial- in the cubital fossa, immediately medial to the biceps tendon
Radial- just proximal to the wrist joint and immediately lateral to the flexor carpi radialis tendon
Ulnar - just proximal to the wrist joint and immediately lateral to the flexor carpi ulnaris tendon
Radial as not covered by a tendon or deep
Which muscles allow supination
Supinator
Biceps- when the elbow is flexed
Which muscles allow pronation
Pronator teres
Pronator quadratus
Flexor muscles of the elbow
Brachioradialis
Biceps brachii
Brachialis
Elbow extensor muscles
Triceps
Pronator muscles
Pronator teres
Pronator quadratus
Supinator muscles
Supinator
Biceps brachii
What percentage of people don’t have Palmaris longus
15%
