Upper Limb: Innervation Flashcards
Describe the general distribution of spinal roots to the Proximal, Intermediate, and Distal Arm.
What are the (3) Trunks? What spinal roots are associated with each?
Superior: C5,6
Middle: C7
Inferior: C8, T1
What are the (3) Cords of the Brachial plexus? Which Trunks are associated with each one?/
Lateral: Superior & Middle
Posterior: Superior, Middle, & Inferior
Medial: Inferior
What are the (5) Terminal branches of the Brachial Plexus? Which cords are associated with each?
Musculocutaneous: Lateral
Axillary: Posterior
Radial: Posterior
Median: Lateral & Medial
Ulnar: Medial
Where does the Dorsal Scapular n. originate?
Off the C5 Spinal Root
Where does the Long Thoracic n. originate?
LT n. originates from the C5, C6, & C7 roots.
Where do the Suprascapular n. & nerve to subclavius originate?
Both the Suprascapular & Nerve to Subclavius originate at the Superior Trunk
Where does the Lateral Pectoral n. originate? What about the Medial Pectoral n.?
The Lateral Pec n. originates at the Lateral cord, while the Medial Pec. n. originates at the Medial cord.
Where do the Subscapular n’s originate in the Brachial Plexus?
What other proximal n. originates here?
The Subscapular n.’s originate at the posterior Cord along with the Thoracodorsal n.
Where do the Medial cutaneous n. of the Arm & Forearm originate?
The Mcut. n’s originate at the Medial Cord
Which muscles does the Musculocutaneous n. innervate?
Sensory innervation region?
Key attributes?
Musculocutaneous n. innervates the Anterior Comp. of the Arm (Flexors)
Sensory innervation of the Lateral Forearm
It pieces through the Coracobrachialis n.
Which muscles does the Axillary n. innervate?
Sensory innervation region?
Key attributes?
The Axillary n. Innervates;
Motor: Deltoid & Teres Minor
Sensory: Upper Lateral Arm
Travels near the Surgical Neck of the humerus with the Posterior Circumflex Humeral a.
Which muscles does the Radial n. innervate?
Sensory innervation region?
Key attributes?
The Radial n. Innervates;
Motor: Posterior Comp. of the Arm & Forearm (Extensors)
Sensory: Lateral & Posterior Arm, Posterior Forearm, Dorsolateral hand
Travels in the radial groove on the posterior aspect of the humerus with the Deep Brachial a.
Which muscles does the Median n. innervate?
Sensory innervation region?
Key attributes?
The Median n. Innervates;
Motor: Most Anterior forearm muscles (flexors) & some hand muscles (Thenar muscles)
Sensory: Lateral Palm & tips of digits 1-3
Travels through the Carpal Tunnel (only nerve to do so)
Which muscles does the Ulnar n. innervate?
Sensory innervation region?
Key attributes?
The Ulnar n. Innervates;
Motor:
- 1 1/2 muscles in Anterior Forearm ( FCU & medial half of FDP)
- Most intrinsic Hand muscles
Sensory:
- Medial Hand
Clinical Landmark
- Travels Just posterior to the Medial Epicondyle of the Humerus
Identify which colors represent cutaneous innervation of that region.
MARMU;
Musculocutaneous: Red
Axillary: Green
Radial: Purple
Median: Blue
Ulnar: Pink
Medial Cutaneous n. of Arm: Light blue
Medial Cutaneous n. of forearm: Yellow
Which nerve innervates the Anterior compartment of the arm?
What is it’s defining characteristic?
What is it’s one exception?
Musculocutaneous n. innervates the anterior arm (Biceps brachii, Coracobrachialis, & Brachialis). It pierces through the Coracobrachialis m. and runs between the biceps brachii & brachialis.
*The brachialis also receives a small contribution by the radial n.
Which nerve innervates the Deltoid & Teres minor?
What is it’s significant landmark?
The Axillary n. innervates the Deltoid & Teres minor.
It travels with the Posterior Circumflex Humeral a. at the surgical neck of the humerus, where it is vulnerable to trauma.
Which nerve Innervates both the posterior arm & posterior forearm?
What is it’s significant landmark/
The radial n. innervates the posterior arm (TB & AN) and forearm (see following).
It travels in the Radial Groove with the Deep Brachial a. of the arm, where it is vulnerable to midshaft fractures.
Posterior arm;
- TB
- AN
- Small contribution to Brachialis
Posterior Forearm;
- Brachioradialis
- Extensor Carpi radialis longus
- Extensor Carpi Radialis Brevis
- Extensor Digitorum
- Extensor Digitorum minimi
- Extensor Carpi Ulnaris
- Supinator
- Extensor Indices
- Adductor Pollicis Longus
- Extensor Pollicis Longus
- Extensor Pollicis Brevis
Which nerve innervates the anterior forearm?
What are the (2) exceptions?
What is it’s clinical landmark?
The Median n. innervates the Anterior Forearm.
It is the Only nerve to pass through the carpal tunnel, where it is susceptible to damage.
Anterior Forearm;
Superficial:
- Pronator Teres
- Flexor Carpi Radialis
- Palmaris Longus
Intermediate:
- Flexor Digitorum Superficialis
Deep:
- Flexor Digitorum Profundus (Lateral 1/2)
- Flexor Pollicis Longus
- Pronator Quadratus
The (2) exceptions of innervation are the Flexor Carpi Ulnaris & Medial 1/2 of the FDP, which are innervated by the Ulnar n.
Which nerve innervates the FCU, the Medial half of the FDP, and most of the hand?
What is it’s clinically significant landmark?
The ulnar n. innervates the FCU, medial half of the FDP, and most of the hand muscles.
The ulnar n. runs just posterior to the medial epicondyle of the Humerus, making it vulnerable to trauma.
Patient presents with a stab would to the upper anterior arm.
Which nerve may be damaged?
What symptoms would be present?
Musculocutaneous n. may be damaged.
Symptoms;
- Motor:
- Difficulty flexing the elbow (& shoulder)
- Difficult supinating the arm
- Absent bicep reflex
- Sensory:
- Numb Lateral Forearm
Patient presents with a fractured humerus at the surgical neck.
Which nerve (and associated artery) may be damaged?
What symptoms would be present?
The Axillary n. & Posterior Circumflex humeral a. may be damaged.
Symptoms;
- Motor:
- Difficulty with;
- Shoulder abduction
- Shoulder flexion
- Shoulder extension
- Shoulder external Rotation
- Difficulty with;
- Sensory:
- Numb Upper lateral arm (Sergeants patch)
Patient presents with a midshaft fracture of the Humerus.
What nerve (and associated artery) may be damaged?
What are the symptoms?
The Radial n. & Deep Brachial a. of the arm may be damaged.
Symptoms;
- Motor
- Difficulty with;
- Extending the elbow
- Extending the wrist
- Finger MCPJ extension
- Absent Triceps reflex & Supinator reflex
- Difficulty with;
- Sensory
- Numb Posterior arm & Forearm
- Numb Radial distribution of hand
Patient presents with trauma to the anterior forearm/wrist.
Which nerve may be damaged?
What symptoms would be present?
The Median n. may be damaged
Symptoms;
- Motor;
- Difficulty with;
- Forearm pronation
- Flexing the Wrist
- Abducting the wrist
- Finger Flexion
- Grip Strength
- Difficulty with;
- Sensory:
- Numb Thenar Eminence
- Numb Median dist. of hand
Patient presents with trauma to the posterior aspect of the medial epicondyle of the humerus.
Which nerve may be damaged?
What symptoms would be present?
The ulnar n. may be damaged.
Symptoms;
- Motor:
- Difficulty with;
- Flexing the Wrist
- Adducting the wrist
- Flexion of the ring & pinky finger
- Finger Abduction
- Difficulty with;
- Sensory:
- Numb Thenar Eminence
- Numb Ulnar dist. of hand.
