Upper Limb 2 Flashcards
what is a nerve plexus?
Formed when peripheral spinal nerve roots split + merge to produce a network of nerves from which new multisegmental peripheral nerves emerge
Plexus supplying upper limb?
Brachial plexus
Plexus supplying lower limbs?
Lumbo-sacral plexus
Describe organisation of brachial plexus from spine → divisions in upper limbs
- The roots enter the inferior neck from the spinal cord where the form trunks.
- Superior (enters from C5 and C6), middle (C7) and inferior trunk (C8 and T1)
- Trunks pass under clavicle to enter axillary region, where they form 6 divisions
- the trunks divide to each give anterior and posterior division (fibres of anterior division supply anterior structures -> posterior innervates posterior structures)
- anterior division from superior and middle trunk form the lateral cord
- single anterior division from inferior trunk forms medial cord
- all 3 posterior divisions merge to form posterior cord
- cords give off terminal branches which are the larger peripheral nerves of the upper limbs
![](https://s3.amazonaws.com/brainscape-prod/system/cm/343/766/758/a_image_thumb.jpeg?1619188509)
Summarise brachial plexus organisation
Roots > trunks > divisions > cords >
How are the cords of the brachial plexus named?
Named according to relationship of axillary artery e.g. posterior cord = posterior to axillary artery
Also named with functional significance-> lateral cord innervates lateral structures, medial cord innervates medial structures +
![](https://s3.amazonaws.com/brainscape-prod/system/cm/343/767/244/a_image_thumb.jpeg?1619189104)
Label this diagram
![](https://s3.amazonaws.com/brainscape-prod/system/cm/343/768/417/q_image_thumb.png?1619190423)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/343/768/417/a_image_thumb.png?1619190405)
Where do spinal nerves leave the spinal cord?
Invertebral foramina of vertebral column
What are the three trunks that form the brachial plexus?
Superior
Middle
Inferior
Which 2 nerves arise from the superior trunk? (supraclavicular branches)
Suprascapular nerve and subclavian nerve
Which spinal nerves form the superior trunk?
Union of anterior rami of c5 & C6
Which root forms the middle trunk?
Directly from anterior rams of C7
Which roots form the inferior trunk?
Arises from anterior rami of C8 and T1
Which nerve is continuous with the lateral cord?
Musculocutaneous nerve
What are supraclavicular branches?
From the roots and the trunks (dorsal scapular nerve, long thoracic nerve)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/343/770/953/a_image_thumb.png?1619191161)
What are infraclavicular branches?
side branches to pectoral girdle muscles and the main peripheral nerves. e.g. branches to some scapular muscles and the large terminal branches e.g. radial, ulnar and median.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/343/771/159/a_image_thumb.png?1619191206)
What nerve is formed from the merger of the terminal parts of the lateral and medial cords (lateral and medial root)?
Median nerve
What nerve is the major terminal branch of the medial cord?
Ulnar nerve
Nerves formed from the lateral or parts of lateral cord?
Musculocutaneous and median nerve (lateral root merges with medial root)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/343/771/427/a_image_thumb.png?1619191372)
What is the musculocutaneous nerve and what does it innervate?
Terminal branch of the lateral cord of the brachial plexus.
Muscular innervation to the anterior muscles of the arm.
Cutaneous innervation of the lateral forearm.
Does the musculocutaneous nerve innervate any muscles in the forearm or hand?
No
Outline pathway of musculocutaneous nerve
- Branches off from the lateral cord of the brachial plexus
- exits the axilla into the anterior arm piercing the coracobrachialis muscle
- It then gives off branches to the biceps and the brachialis muscle.
- Terminal branch of the nerve crosses the elbow
- supplies cutaneous innervation to the anterolateral surface of the forearm
- This branch is termed the lateral cutaneous nerve of the forearm.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/343/771/749/a_image_thumb.jpg?1619191827)
Label this diagram
![](https://s3.amazonaws.com/brainscape-prod/system/cm/343/772/297/q_image_thumb.png?1619191881)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/343/772/297/a_image_thumb.png?1619191890)
What is the ulnar nerve?
Terminal branch of medial cord of the brachial plexus
Where does the ulnar nerve pass?
Passes behind the medial epicondyle of the humerus
Where is the ulnar nerve easily damaged?
Medial epicondyle of the humerus
Outline pathway of ulnar nerve
- passes from axilla to medial aspect of arm
- crosses elbow by passing posteriorly to medial epicondyle of humerus
- after crossing elbow, ulnar nerve gives branches to 2 of the more medial of the anterior forearm muscles
- bulk of the nerve continues to pass distally, crossing wrist at anterolateral aspect
- enters hand to innervate many of intrinsic muscles + region of cutaneous innervation
![](https://s3.amazonaws.com/brainscape-prod/system/cm/343/835/811/a_image_thumb.jpg?1619269762)
Where is the ulnar nerve most palpable and what can this make it more susceptible to?
Medial epicondyle
More susceptible to injury
Does the ulnar nerve innervate the arm?
No innervation on the arm
Where does the ulnar nerve cross to enter the hand?
Crosses the wrist
Does the ulnar nerve innervate the forearm?
Limited innervation in forearm
Does the ulnar nerve innervate the hand?
Cutaneous innervation of the medial aspect of hand (middle half of ring finger and little finger)
What muscles does the ulnar nerve innervate?
Flexor carpi ulnaris muscle
Medial flexor digitorum profundus muscle
Branches to intrinsic hand muscles -> muscles of hypothenar eminence + 2 medial lumbricals (palmar interossei + dorsal interossei)
Cutaneous innervation to medial aspect of hand, including the little finger, and the medial half of the ring finger.
Label this diagram
![](https://s3.amazonaws.com/brainscape-prod/system/cm/343/842/015/q_image_thumb.png?1619269342)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/343/842/015/a_image_thumb.png?1619269359)
How is the median nerve formed?
C6-T1
Branches of lateral cord + medial cord (cores of brachial plexus)
Does the median nerve innervate the arm?
No significant innervation in arm
What does the median nerve innervate?
Most of the anterior forearm muscles
Innervates some intrinsic hand muscles
Cutaneous innervation of lateral hand
Outline pathway of the median nerve
- Passes distally out of the axilla to run medially in arm (no significant branches in the arm)
- Crosses the elbow joint into the forearm where it supplies most of the anterior muscles.
- Passes under flexor digitorum (forms roof of carpal tunnel)
- crosses wrist and enters hand through carpal tunnel
- Supplies thenar eminence muscles + large part of skin of palm and digits