Upper limb nerves (wk11)

Question 1

Draw the system of the brachial plexus

Question 2

Brachial plexus
-Order of roots, trunks, divisions and cords

Answer 2

-The brachial plexus starts at C5, C6, C7, C8 and T1 (the nerve roots – which leave the spinal cord in between 2 vertebrae in the spinal cord) e.g. The C5 root is going to be coming out between the C4 and C5 vertebrae. However, C8 is going to be coming from C7 and T1 as there is no 8th cervical spinal area.
-C5 and C6 join together, the C7 is on its own and C8 and T1 join together
-The roots converse at the trunks. Superior (C5/C6), Middle (C7) and Inferior (C8/T1)
-The trunks then rise to divisions. Superior trunk + Middle trunk = Anterior division. Inferior trunk = Carries on its own as an anterior division. Superior trunk + Middle trunk + Inferior trunk = Posterior division.
-Cords -> Lateral cord is made up of anterior division of superior and middle trunk. Posterior cord is made up of posterior divisions of superior, middle and inferior trunks. Medial cord is made up of anterior divisions of the inferior trunks.
-The divisions run superior and posterior to the clavicle. The divisions then become cords as they run past the armpit of the body.

Question 3

Brachial plexus
-Terminal branches

Answer 3

-Terminal branches -> Lateral cord is going to terminate in the musculocutaneous nerve. The lateral and medial cord are going to give fibres and form the median nerve. The medial cord is also going to give rise to the ulnar nerve. The posterior cord is going to terminate in the axillary nerve and the radial nerve

Question 4

Smaller nerves arising from the brachial plexus
-Root C5, C5/6/7, Superior trunk, Lateral cord, Medial cord, Posterior cord

Answer 4

-Root C5 -> Dorsal scapula nerve (supplies nerves to our scapula and muscles on our back e.g rhomboids and levator scapulae)
-Roots of C5, C6, C7 -> Long thoracic nerve (supplies nerves to our serratus anterior and muscles in protraction of the shoulder blade)
-Superior trunk -> Subclavius muscle and Suprascapula nerve -> Provides innervation to the muscles that sat on the back aspects of the scapula e.g. Supraspinatus and Infraspinatus
-Lateral cord -> Lateral pectoral nerve -> Supply pectoral major and the clavicular head of the pec major
-Medial cord -> Medial pectoral nerve -> Supplies other parts of pec major and some of pec minor. There are also cutaneous nerves which arise off the medial cord – medial cutaneous nerve of the forearm and medial cutaneous nerve of the arm -> They supply some of the skin on the forearm.
-Posterior cord -> Upper and Lower subscapular nerve and middle/Thurrock dorsal nerve. Thurrock dorsal nerve -> Innervating latissimus dorsi. Upper and Lower subscapular nerves -> Innervating Subscapularis. Innervate mostly muscles around the shoulder girdle.

Question 5

Smaller nerves arising from the brachial plexus and the muscle it innervates

Answer 5

-Brachial plexus gives rise to the nerves and innervates these muscles before it gets into the lower peripheral nerves which run down the arm. Explains why we get small nerves branching off before we get into the terminal branches (musculocutaneous, artillery, median, radial, ulnar)
-Dorsal scapular nerve -> Root of C5 -> medial border of the scapula -> innervates scapular and rhomboids
-Long thoracic nerve -> Root of C5, C6, C7 -> serratus anterior -> arises off ribs -> insert into medial border of the scapular -> serratus anterior muscle
-Suprascapular nerve -> Leaves superior trunk -> supplies muscle on back of scapula -> supraspinatus muscles
-Subscapular nerve -> Posterior cord -> supplies subscapularis muscle
-Thurrock dorsal nerve -> innervates latissimus dorsi muscle
-Pectoral nerves -> runs off lateral and medial cords -> pec major and pec minor muscles through pec major/minor nerves

Question 6

Name all of the nerves supplying the following muscles
-Latissimus dorsi, The rhomboids, Supraspinatus, Subscapularis, Pectoralis major

Answer 6

• Latissimus dorsi -> Thurrock dorsal nerve
• The rhomboids -> Root C5 and Dorsal Scapular nerve
• Supraspinatus -> Suprascapular nerve + posterior cord
• Subscapularis -> Subscapular nerve
• Pectoralis major -> Pectoral nerves

Question 7

Peripheral nerve - Posterior Cord
-Describe the broad course and location of the axillary and radial nerves

Answer 7

-Axillary nerve: Posterior cord -> inferiorly wrapping underneath the neck of the humerus -> posteriorly wraps around the rest of the humerus. Muscular innervation: Teres minor and deltoid
-Radial nerve: Posterior compartment of the arm (through a triangle consisting of: teres major, humerus and long head of triceps -> Anteriorly where the brachial plexus is -> Posterior compartment of the upper arm -> Sits alongside the spiral groove of the humerus -> Runs anteriorly down the humerus and slots in just superior to the elbow joints -> Nerve passes back across the front of the elbow joint to form the lateral border to the humerus fossa. Muscular innervation: Muscles of the posterior arm and forearm and the skin of the posterior arm, forearm and dorsum of the hand.

Question 8

Peripheral nerves - Posterior cord
-Describe the sensory distribution of the axillary and radial nerves

Answer 8

-Axillary nerve -> Anterior: Superior lateral cutaneous nerve of the arm. Posterior: Superior lateral cutaneous nerve of the arm.
-Radial nerve -> Anterior (T2): Inferior lateral cutaneous nerve of the arm. Posterior: Inferior lateral cutaneous nerve of the arm, Posterior cutaneous nerve of the arm and Posterior cutaneous nerve of the arm + superficial branch on the posterior of the hand

Question 9

Peripheral nerves - Lateral and medial cords
-Describe the course and location of the musculocutaneous, median and ulnar nerves

Answer 9

-Musculocutaneous: 3rd part of axillary artery om the lower part of the axilla -> Separates coracobrachialis and enters -> Inserts into anterior arm -> Descends between biceps brachii and brachialis muscle. Muscular innervation -> Motor innervation to flexor muscles of the arm
-Median: Arm and cubital fossa -> Travels adjacent to the brachial artery -> Runs in the forearm -> Posterior to the flexor digitorum superficialis, anterior to the flexor digitorum profundus. Accompanied by anterior interosseous artery. Muscular innervation -> Pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis
Ulnar -> Descends on the medial side of the brachial artery -> Pierces medial intermuscular septum to enter the posterior arm -> Passes behind the medial epicondyle of the humerus -> Descends in the forearm -> Nerve enters the palmar aspects of the hand. Muscular innervation -> Medial half of flexor digitorum profundus, flexor carpi ulnaris, palmaris brevis, skin of the medial palmar and dorsal aspect of the hand

Question 10

Peripheral nerves - Lateral and medial cords
-Describe the sensory distribution of the musculocutaneous, median and ulnar nerves

Answer 10

-Musculocutaneous -> Sensory innervation to skin of the lateral side of the forearm and elbow joint. Anterior and Posterior sensory nerve distribution to the lateral cutaneous nerve of the forearm.
-Median nerve -> Sensory and motor innervation. Supplies the elbow, wrist, and intercarpal joints, the anterior muscles of the forearm, muscles of the digits, skin of the palm, thenar eminence.
-Ulnar nerve -> Sensory innervation to the last 2 digits of the hand