Anatomy 17 Flashcards
What does the shaft of the humerus expand distally to form?
Bony prominences called the medial and lateral epicondyles
What are the names of the prominences that the distal humerus bears?
Trochlea
Capitellum
What do the trochlea and capitellum articulate with?
Trochlear notch of the ulna and the head of the radius,
respectively, at the elbow joint
What is the anterior wall of the axilla?
Pectoralis major and minor
What is the posterior wall of the axilla?
Subscapularis
Teres major
Latissimus dorsi
What is the lateral wall of the axilla?
Upper humerus
What is the medial wall of the axilla?
Serratus anterior and chest wall
What is the apex of the axilla?
First rib, clavicle and scapula.
It is the passage between the neck and the axilla
What is the base of the axilla?
Skin and fascia between the chest wall and arm
What is the function of the lymph nodes in the axilla?
Drain the upper limb, chest and the abdominal wall as far as the umbilicus
What is the axillary artery?
The major artery of the upper limb
What is the axillary vein?
The major vein draining the upper limb
What is the function of the brachial plexus?
Innervates the upper limb
How many groups of lymph nodes are in the axilla?
5
Which part of the axilla are the lymph nodes located?
Apex of the axilla
What is the function of the apical nodes?
Receive lymph from all other lymph nodes in the axilla
What disease can the axillary lymph nodes be involved in?
Cancer (metastasis) - as they drain lymph from a large area
Which type of cancer are the axillary lymph nodes particularly associated with?
Breast cancer
What may be the first sign of breast malignancy?
Detection of a lump in the armpit
The axillary artery is a continuation of which artery?
Subclavian artery
Where does the subclavian artery travel through?
Travels under the clavicle and into the axilla
Which branches does the axillary artery give rise to?
one above pectoralis minor,
two behind it and three below it
What does the axillary artery continue into the arm as?
Brachial artery
At what point does the axillary artery become the brachial artery?
As it crosses the inferior border of teres major
What is the axillary vein?
Large vein which drains the upper limb and is continuous with the subclavian vein
What does the axillary vein travel alongside?
Axillary artery
What is the axillary vein formed by?
Union of the deep veins of the arm with the basilic vein
What happens if the axillary vein or artery is injured?
It can cause life-threatening bleeding
How can you halt bleeding of the axillary vessels?
Compress them against the humerus
What is the brachial plexus?
Network of nerves that provides motor and sensory
innervation to the upper limb
What is the brachial plexus formed by?
Spinal nerves C5, C6, C7, C8 and T1
What are the 5 segments of the brachial plexus?
Roots
Trunks
Divisions
Cords
Branches
What are the ‘roots’ of the brachial plexus?
5 spinal nerves (C5 - T1) that exit the spinal cord and collectively give rise to the brachial plexus.
They are found in the neck
What are the ‘trunks’ of the brachial plexus?
Located in the neck
* C5 and C6 combine to form the superior trunk
* C7 continues as the middle trunk
* C8 and T1 combine to form the inferior trunk
What are the ‘divisions’ of the brachial plexus?
Each trunk divides into an anterior and a posterior division under the clavicle
What are the ‘cords’ of the brachial plexus?
Named relative to their position around the second part of the axillary artery
What is the lateral cord of the brachial plexus?
Anterior divisions of the superior and middle trunks combine
What is the posterior cord of the brachial plexus?
Posterior divisions of all the trunks combine
What is the medial cord of the brachial plexus?
Anterior division of the inferior trunk continues as the medial cord
Where are the branches of the brachial plexus located?
In the axilla
What is the axillary branch?
A branch from the posterior cord
What is the radial branch?
The continuation of the posterior cord
What is the musculocutaneous branch?
A branch from the lateral cord
What is the ulnar branch?
A branch from the medial cord
What is the median branch?
Formed by branches from the lateral and medial cords
What does the axillary nerve innervate?
Innervates deltoid and teres minor and a small region of skin over the upper lateral arm
What is the axillary nerve a branch of?
Posterior cord
What spinal nerves does the axillary nerve contain fibres from?
Spinal nerves C5 and C6
What does the axillary nerve run close to?
The surgical neck of the humerus
What is the axillary nerve vulnerable to?
Injury in fractures of the surgical neck of the humerus or dislocations of the humeral head
What does the radial nerve innervate?
- Triceps
- All the muscles in the posterior compartment of the forearm – these muscles are extensors of the wrist and digits
- Regions of skin over the arm, forearm and hand
What is the radial nerve a continuation of?
The posterior cord
What spinal cords does the radial nerve contain fibres from?
C5 - T1
What does the radial nerve run along?
The radial (spiral) groove on the posterior surface of the humerus
Where is the radius vulnerable in?
Radial (spiral) groove, mid-shaft fractures of the humerus
What does the musculocutaneous nerve innervate?
3 muscles in the anterior arm
What does the musculocutaneous nerve arise from?
Lateral cord
What spinal nerves does the lateral cord contain fibres from?
C5 - C7
What does the musculocutaneous nerve continue as?
Sensory nerve that innervates a region of skin over the forearm
What is a benefit of the location of the musculocutaneous nerve?
Rarely injured in isolation
What do the median and ulnar nerves innervate?
Innervate muscles in the anterior forearm and the hand
(Flexors of the wrist and digits)
Small muscles of the thumb. It innervates skin over the
lateral aspect of the palm of the hand and over the lateral digits
Which cords is the medial nerve formed from?
Lateral and Medial
Which spinal fibres does the medial nerve contain fibres from?
C6 - T1
Where is the median nerve most vulnerable?
Cubital fossa - region where it crosses the anterior aspect of the elbow
Which cord is the ulnar formed by the continuation of?
Medial
Which spinal nerves does the ulnar nerve contain fibres from?
C8 - T1
What does the ulnar nerve innervate?
- Most of the small muscles in the hand and therefore is vital for fine movements of the digits
- It also innervates skin over the medial aspect of the hand and medial digits
Where is the ulnar nerve vulnerable to injury?
Behind the medial epicondyle as it lies in a superficial position here
What is the most catastrophic type of brachial plexus injury?
When all five roots of the brachial plexus are injured
What are the 3 muscles found in the anterior compartment of the arm?
Biceps brachii
Brachialis
Coracobrachialis
What do the biceps brachii, brachialis and coracobrachialis act as?
Flexors
What nerve are the biceps brachii, brachialis and coracobrachialis innervated by?
Musculocutaneous nerve
Where does the biceps brachii lie?
Most superficially in the anterior arm
How many muscle bellies does the biceps brachii have?
2 muscle bellies – the long head and the short head
What are both muscle heads of the biceps brachii attached to?
Scapula
Long head to the supraglenoid tubercle
Short head to the coracoid process
What do the two biceps muscle bellies converge via?
Common tendon onto the radial tuberosity of the radius
What does the tendon of the long head pierce?
Pierces the capsule of the shoulder joint and helps to stabilise the joint
What movements does the biceps execute?
Flexion of the elbow joint
Flexion of the shoulder joint
Supination of the forearm when the elbow is flexed
Where is the brachialis located?
Deep to biceps
Where is the brachialis attached?
Attached to the anterior aspect of the lower half of the shaft of the humerus
Where does the brachialis insert?
Inserts distally upon the ulna tuberosity
Where does the brachialis insert?
Inserts distally upon the ulna tuberosity
What movement does the brachialis execute?
Flexion of the elbow
Where does the coracobrachialis attach?
Attaches proximally to the coracoid process of the scapula
Distally to the medial aspect of the middle part of the humerus
What movement does the coracobrachialis execute?
Crosses the shoulder joint and acts upon it as a weak flexor
What is the cubital fossa?
Region anterior to the elbow joint
Referred to as antecubital fossa and abbreviated in medical notes to ‘ACF
What is the lateral border of the cubital fossa?
Formed by brachioradialis, a posterior forearm muscle
What is the medial border of the cubital fossa?
Formed by pronator teres, an anterior forearm muscle
What is the superior border of the cubital fossa?
Formed by an imaginary line drawn between the medial and lateral epicondyles of the humerus
What is the apex of the cubital fossa?
Most distal, ‘pointing’ towards the forearm and hand
Where does the tendon of the biceps brachii travel in the cubital fossa?
Travels to its insertion point on the radial tuberosity
How is the bicep reflex examined?
Biceps tendon is tapped with a tendon hammer
What is the bicipital aponeurosis?
Fascial extension of the biceps tendon
What is the function of the biciptal aponeurosis?
It separates the superficial veins from deeper structures in the fossa; the brachial artery and the median nerve
Where does the brachial artery lie?
Medial to the biceps tendon
What does the brachial artery bifurcate into?
Its terminal branches – the radial and ulnar arteries
– in the cubital fossa
Where is the median nerve located?
Medial to the brachial artery
Does the median nerve innervate any muscles in the arm?
No - travels through the anterior compartment of the arm and the cubital fossa on its journey to the anterior forearm and hand
What does the median nerve innervate?
Muscles in the anterior forearm and hand
What does the radial nerve pass through?
Lateral aspect of the cubital fossa
Where is the radial nerve located?
Deep to the brachioradialis
Why are the superficial veins that lie in the subcutaneous tissue over the cubital fossa clinically important?
Commonly accessed for:
* venepuncture (taking blood)
* intravenous access (i.e. placing a cannula for administering fluids or drugs)
What nerves are at risk when removing axillary lymph nodes?
Long thoracic nerve
Thoracodorsal nerve
What does the long thoracic nerve innervate?
Serratus anterior
Where is the long thoracic nerve located?
Lies superficially on the surface of the muscle in the medial wall of the axilla
What happens if there is an injury to the long thoracic nerve?
Causes weakness or paralysis of serratus anterior
What is the function of the serratus anterior?
Hold the medial border of the scapula flat against the posterior chest wall
What would happen if the serratus anterior were paralysed?
the medial border lifts off the chest wall and appears to ‘stick out’. This is called a ‘winged’ scapula
Why is the thoracodorsal nerve vulnerable to injury?
Runs along the subscapularis muscle, which forms the posterior wall of the axilla
Why is the ulnar nerve vulnerable in the lower arm?
As it travels behind the medial epicondyle
– it is superficial here
What may injure the ulnar nerve?
Fractures of the medial epicondyle
What may injury to the ulnar nerve lead to?
Motor impairments of the hand (as it innervates most of the small muscles of the hand)
and causes sensory impairment in the hand (the medial side of the hand and the medial 1½ fingers)
What happens if you bang your elbow in the region of the ulnar nerve?
The region is referred to as the ‘funny bone’.
A blow to the nerve here causes pain and tingling in the same regions of the hand
What is the injury to the upper brachial plexus referred to?
‘Erb’s Palsy’
What spinal cords are involved when the upper brachial plexus is injured?
C5 - C6, or C5 - 7
What happens when the upper brachial plexus is injured?
Paralysis of the lateral rotators of the shoulder and the extensors of the wrist
The affected limb typically appears medially rotated with the wrist flexed
What can injury to the upper brachial plexus be caused by?
Typically caused by trauma – specifically mechanisms that stretch the head away from the shoulder.
This is typically seen when someone is thrown from a motorbike or a horse.
It may also be seen in newborns if the baby’s shoulder becomes stuck during delivery and its neck is excessively stretched
What is injury to the lower brachial plexus referred to?
‘Klumpke’s Palsy’
What spinal cords are involved when the lower brachial plexus is injured?
Typically C8 and T1
What happens when the lower brachial plexus is injured?
Paralysis of the small muscles of the hand
What can injury to the lower brachial plexus be caused by?
Typically caused by trauma – specifically mechanisms that forcefully and suddenly pull the arm upwards – this stretches the lower nerves of plexus.
It may be sustained by babies during delivery if the arm is forcefully pulled.
What is horner’s syndrome?
Triad of drooping of the eyelid (ptosis),
a constricted pupil (miosis) and
lack of sweating (anhidrosis) on one side of the face
What is horner’s syndrome a result of?
Sympathetic nerve supply to the face is interrupted
Which spinal nerve carries sympathetic fibres which are destined to supply the face?
T1
What is a brachial plexus block?
Form of regional anaesthesia and can be used as an alternative to general anaesthesia for surgery on the upper limb
