Forearm Flashcards
Where do the superficial veins lie within the forearm?
Within the subcutaneous fat
What is the common origin of the flexor muscles of the forearm?
Medial epicondyle
How many layers of muscles are there within the anterior compartment, what are they?
1) Superficial
2) Intermediate
3) Deep
What are the superficial muscles of the anterior compartment of the forearm?
Medial to lateral
1) Flexor carpi ulnaris
2) Palmaris longus
3) Flexor carpi radialis
4) Pronator teres
What shape is the pronator teres muscle?
Cyclindrical
What characterises the palmaris longus muscle?
Small muscle with very long tendon
Which muscle makes up the intermediate layer of the anterior compartment?
Flexor digitorum superficialis
How many tendons does flexor digitorum superficialis split into and where do they pass?
Splits into 4 tendons, they pass through the carpal tunnel
What lies on the underside of flexor digitorum superficialis?
Median nerve
Which muscle lies deep to flexor digitorum superficialis?
Flexor digitorum profundus
Which muscles make up the deep layer of the anterior compartment?
Flexor digitorum profundus
Flexor pollicis longus
Pronator quadratus
How many tendons does flexor digitorum profundus split into and where do they pass?
Splits into 4 tendons, pass through the carpal tunnel
Which muscle lies in the deep layer of the anterior compartment lateral to flexor digitorum profundus?
Flexor pollicis longus
Which muscle lies deepest in the deep layer of the anterior compartment of the forearm and where does it run from and to?
Pronator quadratus, can be viewed by separating flexor digitorum profundus and flexor pollicis longus, runs from radius to ulnar
What is the common origin of the extensor muscles of the forearm?
The lateral epicondyle
Which muscle is most lateral/radial in the superficial layer of the posterior compartment of the forearm?
Brachioradialis
What is unusual about brachioradialis muscle?
So far to the radial side that its almost in the anterior compartment
Considered part of the posterior/extensor compartment but it acts as a flexor of the arm
How many layers of muscles make up the posterior compartment of the forearm what are they called?
1) Superficial layer
2) Deep layer
Which muscle lies medial to brachioradialis in the posterior compartment of the forearm?
Extensor carpi radialis longus
From lateral to medial which muscles make up the superficial layer of the posterior compartment of the forearm?
1) Brachioradialis
2) Extensor carpi radialis longus
3) Extensor carpi radialis brevis
4) Extensor digitorum (lies in the midline)
5) Extensor digiti minimi
6) Extensor carpi ulnaris
How many tendons does extensor digitorum split into where do they pass?
Splits into 4 tendons which pass deep to the extensor retinaculum
Which 4 muscles make up the deep layer of the posterior compartment of the forearm from medial to lateral?
1) Extensor indicis
2) Extensor pollicis longus
3) Extensor pollicis brevis
4) Abductor pollicis longus
Abductor pollicis longus muscle wraps around what?
The radius
Which tendons form the medial and lateral boundaries of the anatomical snuff box?
Medial boundary - Tendon of extensor pollicis longus
Lateral boundary - tendons of extensor pollicis brevis and abductor pollicis longus
Why is the anatomical snuff box important clinically?
Running along the floor of it is the radial artery so its a pulse point
Its also an area to palpate the carpal bones in suspected fractures
What is the role of supinator muscle and what compartment is it found in?
Found in the deep layer of extensor compartment
Wraps around the radius, works together with biceps brachii to supinate the forearm
What is the cubital fossa?
Triangular shaped area anterior to the elbow
What are the boundaries of the cubital fossa?
Lateral = brachioradialis Medial = pronator teres Superiorly = imaginary line between the 2 epicondyles of the humerus
What muscle forms the floor of the cubital fossa?
Brachialis
What forms the roof of the cubital fossa?
Deep fascia of the forearm and the bicipital aponeurosis
What is the bicipital aponeurosis?
Thickening of the deep fascia that runs medially from the bicipital tendon
What are the contents of the cubital fossa?
Tendon of biceps brachii (most lateral) Brachial artery Median nerve (most medial)
What happens to the brachial artery at the level of the cubital fossa?
At this level the brachial artery divides into the radial and ulnar arteries
Do superficial veins lie within the cubital fossa?
No they lie superior to the roof, they lie within the subcutaneous fat
Which superficial vein lies laterally?
Cephalic vein
Which superficial vein lies medially?
Basilic vein
Which vein joins the cephalic and basilic vein, why is it important clinically?
Median cubital vein
Blood is normally sampled from the median cubital vein
Why is the median cubital vein still a safe place to sample blood from in spite of lying superficial to the brachial artery and median nerve?
The brachial artery and median nerve are protected by the roof of the cubital fossa
Which ligament holds the radius in place at the superior radioulnar joint and what are its attachments?
Annular ligament
Proximal attachment = anterior margin of radial notch of ulnar
Distal attachment = posterior margin of radial notch of ulnar from trochlear notch to supinator crest
In pronation what happens to the position of the ulna and radius?
Radius crosses over the top of the ulna
What is the anatomical name for the wrist joint?
Radiocarpal joint
Which carpal bones articulate with the radius at the radiocarpal joint?
The lunate and scaphoid bones
Why are multiple x-rays of the scaphoid necessary?
Because of the small size and shape of scaphoid, you would need a series of x rays to identify a fracture
How can a fall on an outstretched hand result in compression of the median nerve?
Because a fall on an outstretched hand can result in dislocation of the lunate bone leading to compression of the median nerve
What effect would median nerve damage from dislocation of the lunate bone have on movements of the digits?
Would affect digit 1 and 2
Supplies 1st and 2nd lumbricals so lose flexion at the metacarpophalangeal joint and extension at the interphalangeal joint
Wouldnt be able to abduct, flex or oppose thumbs as thenar muscles are supplied by the median nerve
Other than brachioradialis what other muscle may be considered to make up the lateral border of the cubital fossa?
Supinator
What happens to the brachial artery at the level of the cubital fossa?
Brachial artery normally bifurcates into the radial and ulnar arteries at the apex of the fossa
Which superficial vein runs more medially on the anterior forearm?
The basilic vein
Which superficial vein runs more laterally on the anterior forearm?
The cephalic vein
Which vessel joins the basilic and cephalic vein?
Median cubital vein
What effect would damage to the median nerve in the cubital fossa have on the movements of the upper limb?
Difficulty in flexing the wrist as the median nerve supplies many of the anterior flexors of the wrist
Difficulty flexing the digits at the metacarpophalangeal and interphalangeal joints
Where does the ulnar nerve run past the elbow joint?
Behind the medial epicondyle
What divides the arm into anterior and posterior compartments?
The deep fascia
Other than pronating the arm what else does pronator teres do?
Acts as a weak flexor of the forearm
Other than flexion of the wrist, what actions do flexor carpi radialis and ulnaris produce?
Flexor carpi radialis - flexes and abducts the wrist
Flexor carpi ulnaris - flexes and adducts the wrist
Palmaris longus is present in approximately what percentage of individuals?
85%
What is the nerve supply of brachioradialis?
radial nerve
Brachioradialis is particularly important in what action?
Returning the forearm to the midprone position from either full supination or full pronation
To which phalanges does flexor digitorum superficialis attach?
Middle phalanges of digits 2-5
Where does the median nerve lie in relation to flexor digitorum superficialis?
Deep to flexor digitorum superficialis
Which neurovascular bundle lies median to flexor digitorum superficialis?
Ulnar nerve and artery
Where do the tendons of flexor digitorum profundus insert?
Onto the palmar surfaces on the distal phalanges of digits 2-5
What is the interosseous membrane and where is it located?
A thin, fibrous sheet which connects the medial border of the radius with the lateral border of the ulna
Free upper margin is situated just inferior to the radial tuberosity, it also has a small circular aperture in the distal 1/3
In which direction do the collagen fibres run in the interosseous membrane?
Run predominantly inferiorly from the radius to the ulna
What are the 3 roles of the interosseous membrane?
1) Connects the radius and ulna restricting pronation and suppination
2) Provides attachment for muscles in the anterior and posterior compartments
3) Orientation of the collagen fibres is consistent in its role of transferring forces from the radius to the ulna and ultimately from the hand to the humerus
Which 4 structures run through the carpal tunnel?
1) Flexor pollicis longus tendon
2) Flexor digitorum superficialis tendons
3) Flexor digitorum profundus tendons
4) Median nerve
Which structures pass deep to the extensor retinaculum?
Tendons of extensor digitorum and digiti minimi
Which compartment is anconeus muscle part of and where is it situated?
Superficial posterior
Small muscle located on the posterior compartment of the elbow
Where does anconeus insert and what is its function?
Inserts into the olecranon and proximal posterior surface of the ulna
Its function is abduction of the ulna and is an accessory extensor of the elbow joint
The deep extensor muscles arise from what generally?
The shaft of the radius and ulna and the interosseous membrane
Which vein runs over the anatomical snuff box?
The cephalic vein
What bony elements can be palpated in the floor of the anatomical snuff box?
Floor is formed by the scaphoid and trapezium carpal bones
Which 2 muscles are responsible for pronation of the forearm?
Pronator teres and pronator quadratus
Which 2 muscles are responsible for supination of the forearm and how powerful are they?
Biceps - superficial and powerful
Supinator - deeper and less powerful
