Week 3: The Arm and Elbow Flashcards
What is the brachial plexus and where is it located?
- nerve network that innervates the upper limb
- located in the neck and the axilla
Explain how the brachial plexus is divided:
- Roots
- Trunks
- Divisions (anterior or posterior)
- Cords
- Branches
The brachial plexus is composed of ventral rami of spinal nerves from which spinal cord segments?
C5-T1
How do spinal nerves transmit sensory and motor information?
- spinal nerves contain motor information that goes out to muscles to stimulate contraction
- sensory information also comes in from the body, back through the spinal nerves into the CNS
What are the 5 terminal branches of the brachial plexus?
- Musculocutaneous
- Axillary
- Median
- Radial
- Ulnar
What happens to anterior and posterior rootlets?
they join together to form a spinal nerve and exit through the vertebral foramen
How is a spinal nerve divided after it leaves the cord?
- into an anterior (ventral) ramus and a posterior (dorsal) ramus
- anterior ramus is larger
Which spinal cord roots do each of the terminal divisions of the brachial plexus come from?
- Musculocutaneous - C5-7
- Axillary - C5-6
- Median - C5-T1
- Radial - C5-T1
- Ulnar - C8-T1
What does the musculocutenous nerve supply?
muscles of the anterior arm, skin of the arm
What does the axilllary nerve supply?
deltoid, teres minor and skin on upper lateral arm
What does the radial nerve supply?
- posterior arm and forearm muscles
- skin of the arm and hand
What does the median nerve supply?
-most anterior forearm muscles, small muscles of the thumb, skin of the hand
What does the ulnar nerve supply?
2 anterior forearm muscles, most small muscles of the hand, skin of the hand
What forms the superior trunk of the brachial plexus?
C5 and C6 joining together
What forms the inferior trunk of the brachial plexus?
C8 and T1 join together
What forms the middle trunk of the brachial plexus?
C7
How is the BP divided after its divided into superior, middle and inferior trunks
Into anterior and posterior divisions:
- posterior divisions of each trunk come together
- the anterior division of the superior and middle trunk come together
- the anterior division of the inferior trunk continues on its own
After the BP has divided into anterior and posterior divisions, what is the next segment?
The chords:
- Lateral cord - formed from the anterior division of the superior and middle trunk
- Posterior chord - formed from the posterior divisions of all the trunks
- Medial chord - formed by the anterior division of the inferior trunk
What are the chords named after?
their position in relation to the axillary nerve
Which bones does the distal humerus articulate with?
ulna and radius
Which 3 bones are involved in the elbow joint?
- humerus
- ulna
- radius
Which 3 joint articulations are present for the elbow joint?
- humero-ulnar = between trochlea and trochlear notch
- humero-radial = between capitulum and radial head
- proximal radio-ulnar joint = between the radial head and radial notch of the ulnar
What features are found on the anterior surface of the distal humerus?
- lateral and medial supracondylar ridge
- lateral and medial epicondyle
- coronoid fossa
- capitulum
- trochlea
What features are found on the posterior surface of the distal humerus?
- olecranon fossa
- trochlea
Which ligament reinforces the elbow joint laterally?
radial collateral ligament
Which ligament reinforces the elbow joint medially?
ulnar collateral ligament
What type of joint is the elbow and which movements does it allow?
Elbow is a hinge joint
We can only flex and extend
Which joint allows pronation and supination (turning it up and down) of the hand?
radioulnar joint
What action does the anterior muscle compartment of the arm have on the elbow?
Allows flexion (bending) of the elbow
What action does the posterior muscle compartment of the arm have on the elbow?
Allows extension (straightening) of the elbow
What are the 3 muscles of the anterior arm?
- Biceps
- Brachialis
- Coracobrachialis
Which nerve are the muscles of the anterior arm innervated by?
Musculocutaneous nerve (C5-C7)
Biceps have 2 heads. What is the short head attached to?
The coracoid process of the scapula
What is the long head of the biceps attached to?
supraglenoid tubercle of the scapula
What is the bicep attached to distally?
radial tuberosity
What is the function of the biceps?
- flexes the elbow and shoulder
- powerful supinator of the forearm when the elbow is flexed
Where is the brachialis?
deep to biceps
What is the proximal and distal attachment of the brachialis?
Proximal attachment - humeral shaft
Distal attachment - ulna
What is the function of brachialis?
flexes the elbow
What is the proximal and distal attachment of the coracobrachialis?
proximal attachment - attach to coracoid process
distal attachment - humeral shaft
What is the function of the coracobrachialis?
Weak flexor of the shoulder
Which muscle is found in the posterior arm?
triceps
Which nerve innervates the triceps?
radial nerve
What are the 3 heads of the triceps muscle and what do each attach to?
- Long head - attaches to the infraglenoid tubercle on the scapula
- Lateral head - attaches proximally to the posterior shaft of the humerus
- Medial head - deep to the long and lateral heads, attached to the shaft of the humerus
Where do all of the tricep heads insert onto?
the olecranon of the ulna
what does the axillary artery give rise to?
brachial artery
What does the brachial artery give rise to?
the deep artery of the arm (profunda brachii)
Which nerves are at risk if you fracture:
- Surgical neck of humerus
- Radial groove of humerus
- Medial epicondyle
- Axillary nerve
- Radial nerve
- Ulnar nerve
What is another word for medial epicondyle?
funny bone - the painful sensation is when you hit your ulnar nerve
What is the term for a trapped muscle or tendon?
impingement
What is a ‘pulled elbow’ in children
- injury where force causes radial head to subluxate from anular ligament
- lump caused by displacement of head of radius
- muscle pulls radial head superiorly
What is ‘golfers elbow’?
medial epicondylitis = inflammation at the medial epicondyle
What is ‘tennis elbow’?
lateral epicondylitis = inflammation at the lateral epicondyle
What is a bursae?
fluid filled sacs located around the joints
What is bursitis?
inflamed bursae
Which nerve is at risk in a humeral supracondylar fracture?
median nerve
The axillary and radial nerve come from which cord
posterior cord
The medial nerve comes from which cord?
lateral and medial
The anterior divisions of the superior and middle trunks combine to form the?
lateral cord
The C8 and T1 spinal nerves form which trunk?
inferior trunk
What does the capitulum articulate with?
the head of the radius
What structure is lateral to the capitulum?
trochlea
What is the attachment site for brachialis?
ulnar tuberosity
Where does pronation and supination occur?
at the proximal and distal radio-ulnar joint
What is a tendon and what colour are they?
- a tendon is a tough band of fibrous connective tissue that connects muscle to bone
- has a whiteish appearance
Where is the infraglenoid tubercle? (the attachment site for the long head of triceps)
Just below the glenoid fossa
What are the boundaries of the cubital fossa?
- an imaginary line across the lateral and medial epicondyles
- the pronator teres muscle
- brachioradialis
Where does the brachial artery bifurcate into the radial and ulnar artery?
at the region of the cubital fossa
Which nerve runs along side the brachial artery?
median nerve
Which nerve runs down the medial aspect of the arm and hooks around the medial epicondyle?
ulnar nerve
What structures run in the radial groove?
Profunda brachii artery and radial nerve
Which artery supplies the posterior compartment of the arm?
profunda brachii artery
How do we test the triceps reflex?
To test the triceps reflex, the patient’s arm is held across their body and the weight of the limb supported. The examiner palpates the triceps tendon superior to its insertion onto the olecranon process and taps it with the tendon hammer.