MSK Upper Arm and Forearm Flashcards
Okay lets start with the muscles of the anterior compartment of the upper arm.
Can you name them?
Biceps brachii- long and short head
Brachialis
Coracobrachialis
What is the innervation for the nerves in the anterior compartment of the upper arm?
Musculocutaneous nerve
What is the overall compartment function for the anterior compartment of the upper arm?
Flexion
Time to get a bit more specific :)
Let’s start with the biceps brachii.
What is it’s action?
Flexion at the elbow joint
Supination of the forearm
What is the action of the brachialis?
Flexion at elbow joint
What is the function of the coracobrachialis?
Flexion at shoulder joint
Weak adduction at shoulder joint
Yay, pretty simple :)
Now let’s move onto the posterior compartment of the upper arm.
What muscle is found here?
Triceps brachii- long, medial and lateral head
One of the heads of the triceps is deep to the other two.
Which one?
Medial head lies deep to the lateral and long heads
Where do the heads of the triceps originate from?
Lateral- superior to radial groove of humerus
Medial- inferior to radial groove of humerus
Long- infraglenoid tubercle of scapula
The three heads of the triceps come together to form a common tendon. Where does this tendon insert?
Olecranon of ulna
What is the innervation for the posterior compartment of the upper arm?
Radial nerve
Oops let me go back for a minute
What are the nerve roots of the musculocutaneous nerve?
C5-7
What are the nerve roots for the radial nerve?
C5-T1
What is the action of the posterior compartment of the upper arm?
Extension of elbow joint
Moving onto the forearm…
How many layers of muscles are there in the anterior compartment of the forearm?
Three- superficial, intermediate and deep
Name the muscles in the superficial layer of the anterior compartment of the forearm.
Flexor carpi ulnaris
Flexor carpi radialis
Palmaris longus
Pronator teres
What is the innervation of the superficial layer of the anterior compartment of the forearm and what is the exception to this?
Supplied by median nerve except for flexor carpi ulnaris which is supplied by the ulnar nerve
What are the muscles in the intermediate layer of the anterior compartment of the forearm
Flexor digitorum superficialis
What is the innervation of the flexor digitorum superficialis, the only muscle in the intermediate layer of the anterior compartment of the forearm?
Median nerve
What are the muscles in the deep layer of the anterior compartment of the forearm?
Flexor pollicus longus
Flexor digitorum profunda
Pronator quadratus
What is the innervation for the deep layer of the anterior compartment of the forearm and what is the exception to this?
Median nerve
EXCEPT for flexor digitorum profundus- medial half (right and little finger) get innervation from the ulnar nerve and lateral half (middle and index) gets innervation from median nerve
Let’s talk about the actions of the muscles in the anterior compartment of the forearm, starting with the superficial layer.
What is the action of the flexor carpi ulnaris?
Flexion at wrist
Adduction of wrist
Let’s talk about the actions of the muscles in the anterior compartment of the forearm, starting with the superficial layer.
What is the action of the flexor carpi radialis?
Flexion at wrist
Abduction of wrist
Let’s talk about the actions of the muscles in the anterior compartment of the forearm, starting with the superficial layer.
What is the action of the palmaris longus?
Flexion at wrist
Let’s talk about the actions of the muscles in the anterior compartment of the forearm, starting with the superficial layer.
What is the action of the pronator teres?
Pronation of the forearm
Let’s talk about the actions of the muscles in the anterior compartment of the forearm, continuing with the intermediate layer.
What is the action of the flexor digitorum superficialis?
Flexion at MCP joints
Flexion at PIP joints
Flexion at wrist
Let’s talk about the actions of the muscles in the anterior compartment of the forearm, finishing with the deep layer.
What is the action of the flexor digitorum profundus?
Flexion of DIP joints
Flexion of MCP joints
Flexion of wrist
Let’s talk about the actions of the muscles in the anterior compartment of the forearm, finishing with the deep layer.
What is the action of the flexor pollicus longus?
Flexes IP joints and MCP joints of thumb
Let’s talk about the actions of the muscles in the anterior compartment of the forearm, finishing with the deep layer.
What is the action of the pronator quadratus?
Pronation of the forearm
Which muscle in the anterior compartment of the upper arm can be absent in approx. 15% of the population?
Palmaris longus
Okay, let’s move onto the posterior compartment of the forearm now :)
Just to recap (mostly to help me making the flashcards haha), so far we have covered the anterior and posterior compartments of the upper arm and the three layers (superficial, intermediate and deep) of the anterior compartment of the forearm.
So, what are the two layers of muscles in the posterior compartment of the forearm?
Superficial and deep
What are the muscles found in the superficial layer of the posterior compartment of the forearm?
There’s quite a few!!
Brachioradialis
Extensor Carpi Radialis Longus
Extensor Carpi Radialis Brevis
Extensor Carpi Ulnaris
Extensor Digitorum
Extensor Digiti Minimi
Anconeus
What is the innervation for the muscles of the superficial layer of the posterior compartment of the forearm?
Radial nerve
Let’s work out the actions of the muscles in the superficial layer of the posterior compartment of the forearm before moving onto the deep layer.
What is the action of the brachiradialis muscle?
Flexion at elbow
->only muscle which breaks the rule that flexors are found in the anterior compartment
Let’s work out the actions of the muscles in the superficial layer of the posterior compartment of the forearm before moving onto the deep layer.
What is the action of the extensor carpi radialis longus and brevis?
Extends the wrist
Abducts the wrist
Let’s work out the actions of the muscles in the superficial layer of the posterior compartment of the forearm before moving onto the deep layer.
What is the action of the extensor carpi ulnaris?
Extends the wrist
Adducts the wrist
Let’s work out the actions of the muscles in the superficial layer of the posterior compartment of the forearm before moving onto the deep layer.
What is the action of the extensor digitorum?
Extension of digits at interphalangeal joints and MCP joints
Let’s work out the actions of the muscles in the superficial layer of the posterior compartment of the forearm before moving onto the deep layer.
What is the action of the extensor digiti minimi?
Extends little finger
Contributes the extension at wrist
Let’s work out the actions of the muscles in the superficial layer of the posterior compartment of the forearm before moving onto the deep layer.
What is the action of the anconeus?
Extends elbow joint
Abducts ulna during pronation
Right, onto the deep layer of muscles :)
Name the muscles found in the deep layer of the posterior compartment of the forearm.
Supinator
Abductor Pollicus Longus
Extensor Pollicus Brevis
Extensor Pollicus Longus
Extensor Indicis
Innervation of the muscles in the deep layer of the posterior compartment of the forearm?
Radial nerve
Let’s work out the actions of the deep muscles in the posterior compartment of the forearm!
What is the action of the supinator muscle?
Supinates forearm
Let’s work out the actions of the deep muscles in the posterior compartment of the forearm!
What is the action of the abductor pollicus longus?
Abducts thumb
Let’s work out the actions of the deep muscles in the posterior compartment of the forearm!
What is the action of the extensor pollicus brevis?
Extension at MCP joints and carpometacarpal joints of thumb
Let’s work out the actions of the deep muscles in the posterior compartment of the forearm!
What is the action of the extensor pollicus longus?
Extends all joints of thumb; CMC, MCP, IP
Let’s work out the actions of the deep muscles in the posterior compartment of the forearm!
What is the action of the extensor inidicis?
Extension of the index finger
Just more generally now, what is the point on the humerus where the tendon of the wrist flexor muscles attach?
Medial epicondyle of humerus
Just more generally now, what is the point on the humerus where the tendon of the wrist extensor muscles attach?
Lateral epicondyle of humerus
Borders of cubital fossa?
Please sit and work them out on yourself, before or after flipping the card over x
Lateral- medial border of brachioradialis
Medial- lateral border of pronator teres
Superior- line between two epicondyles of humerus (imaginary)
Roof- bicep aponeurosis, fascia, subcutaneous fat and skin
Floor- brachialis and supinator
Contents of cubital fossa?
Radial nerve
Median nerve
Brachial artery
Biceps tendon (can feel if flex arm)
What makes up the anatomical snuff box?
Look at hand pls
Ulnar border- tendon of extensor pollicis longus
Radial border- tendons of extensor pollicis brevis and abductor pollicis longus
Muscles of the hand can be extrinsic or intrinsic. We have already covered the extrinsic ones as they are located within the anterior and posterior compartments of the forearm.
What are the groups of intrinsic muscles of the hand?
Thenar muscles
Hypothenar muscles
Lumbricals
Interossei
Name the thenar muscles.
Opponens pollicis
Abductor pollicis brevis
Flexor pollicus brevis
Innervation of thenar muscles?
Median nerve
(but deep head of flexor pollicus brevis is innervated by ulnar nerve branch)
Time for the action of the thenar muscles :)
What is the action of the opponens pollicis?
Oposes thumb
Time for the action of the thenar muscles :)
What is the action of the abductor pollicis brevis?
You’ll never guess it… it abducts the thumb
Time for the action of the thenar muscles :)
What is the action of the flexor pollicis?
Flexion of MCP joint of thumb
Okay, where would you find the thenar muscles?
Base of thumb on palmar aspect of hand
Where would you find the hypothenar muscles?
Base of little finger on palmar aspect of hand
Name the hypothenar muscles.
Opponens digiti minimi
Abductor digiti minimi
Flexor digiti minimi brevis
Innervation of the hypothenar muscles?
Ulnar nerve
Right, time for the actions of the hypothenar muscles!
What is the action of the opponens digiti minimi?
Opposition by moving little finger towards palm
Right, time for the actions of the hypothenar muscles!
What is the action of the abductor digit minimi?
Abduction of the little finger
Right, time for the actions of the hypothenar muscles!
What is the action of the flexor digiti minimi brevis?
Flexion of MCP joint of little finger
How many lumbrical muscles are there?
Four- one for each finger
What are the actions of the lumbricals?
Flexion at MCP joints
Extension at IP joints
Describe the innervation of the lumbricals.
Lateral two lumbricals (index and middle) = median nerve
Medial two lumbricals (ring and little) = ulnar nerve
RECAP-
nerve roots of
1. Musculocutaneous
2. Radial
3. Ulnar
4. Median
- C5-7
- C5-T1
- C8-T1
- C6-T1
What are the two types of interossei?
Dorsal and palmar
What is the innervation of all the interossei?
Ulnar nerve
->C8-T1
Action of the palmar interossei?
Adduction of digits (PAD)
Assist with flexion at MCP joints and extension at IP joints
Action of dorsal interossei?
Abduction of digits (DAB)
Assists with flexion at MCP joints and extension at IP joints