Brachial Plexus Flashcards
Where do all the major nerves that innervate the upper limb originate?
brachial plexus
What is the brachial plexus and how is it formed?
somatic plexus formed by the anterior rami of spinal nerves C5 to C8 and T1
Describe the path of the brachial plexus from origin to end.
It originates in the neck, passes laterally and inferior over rib 1 enters the axilla and associates with the axillary artery
What are the parts of the brachial plexus from proximal to distal?
roots, trunks, divisions, cords and terminal branches
What 2 functions do the terminal branches provide?
Motor innervation to the muscles of the upper limb sensory innervation to specific regions of the skin.
What happens when a nerve is completely severed at a particular location?
function of the nerve proximal to the injury is normal and the function of the nerve distal to the injury is lost, resulting in loss of muscle function and regions of numbness on the skin.
What terminal branch of the lateral cord immediately enters the anterior compartment of the arm and runs between the brachialis and biceps brachii?
musculocutaneous nerve
Describe the path of the median nerve.
is a terminal branch from the lateral and median cords in the axilla and runs distally in association with the brachial artery in the medial aspect of the arm. Crosses anterior to the elbow join and enters the forearm. The upper part of the forearm the median nerve gives off a deep branch (anterior interosseous n.) and continues through the forearm into the hand through the carpal tunnel.
In the upper part of the forearm the median nerves gives off a deep branch of what nerve?
anterior interosseous nerve
Describe the path of the ulnar nerve.
a terminal branch of the medial cord that runs distally in association with the brachial artery and median nerve in the medial aspect of the arm. The nerve passes posterior to the medial epicondyle of the humerus and enters the forearm. The nerve travels down the medial aspect of the forearm close to the ulna and divides into a superficial and deep branch of the wrist.
What nerve is a terminal branch of the posterior cord that exits through the posterior wall of the axilla and passes posterior to the surgical neck of the humerus?
axillary nerve
Describe the path of the radial nerve.
terminal branch of the posterior cord that passes out the axilla into the posterior compartment of the arm in close association to the posterior aspect of the shaft of the humerus. The nerve enters the forearm posterior to the lateral epicondyle of the humerus and travels to the posterior aspect of the hand. As it travels through the forearm it gives off a deep branch the posterior interosseous nerve.
What deep branch comes off the radial nerve as it passes through the forearm?
posterior interosseous nerve
Loss of a nerve to a muscle results in what?
atrophy/disuse of that muscle
Movement that is accomplished by 2 or more muscles innervated by different nerves will result in what when only one of the nerves is damaged?
weakness of movement
Movement that is accomplished by muscles that are all innervated by the same nerve will result in what when the nerve is damaged?
completely loss of movement
Loss of muscle function nearly always results in what?
opposite function/motion being dominant
In addition to motor deficits injury to a nerve is often associated with what?
sensory loss
What are the 2 most common injuries to the axillary nerve?
anterior dislocation of the humerus and a fracture of the surgical neck of the humerus
What is the most common site of injury to the radial nerve?
midshaft fractures of the humerus
What are the motor and sensory deficits with anterior dislocation fo the glenohumeral joint and fracture of the surgical neck of the humerus?
Motor: weakness of the arm abduction Sensory: lateral shoulder and upper arm
What are the motor and sensory deficits with mid shaft fracture of the humerus?
Motor: loss of wrist and digit extension, weakness of hand and forearm supination sensory: posterior arm and forearm and dorsal of hand.
What are the most common injuries to the median nerve?
fractures of the elbow and distal humerus or within the carpal tunnel (carpal tunnel syndrome)
What are the motor and sensory deficits with a supraepicondylar fracture of the humerus?
Motor: weakness of wrist flexion, loss of index and middle finger flexion, weakness of thumb abduction, loss of thumb opposition and flexion, loss of pronation Sensory: palmar aspect of thumb, Palma r and dorsal aspect of index, middle and half of ring finger.
