Neurology of the thoracic limb

Question 1

What are the roots of the brachial plexus?

Answer 1

C6, C7, C8, T1 and T2

Question 2

Route and connections of N. suprascapularis

Answer 2

• Enters the intermuscular space between m. supraspinatus ans m. subscapularis.
• Accompanied by the supraspinous artery and vein.

Question 3

What does N. suprascapularis innervate?

Answer 3

• After passing over the scapular notch, innervates m. supraspinatus.
• Sends a small branck to the lateral part of the shoulder joint.
• Continues across the scapular neck to the end of the spine, where it innervates m. infraspinatus

Question 4

Origin of Nn. subscapularis

Answer 4

• Usually a single, but occasionally double.
• Arises from the union of a branch from C6 nerve with C7 nerve.
• Divides into cranial and caudal part, before entering the medial surface of m. subscapularis.
• Only 5cm long. Allows extensive sliding movement in the shoulder.

Question 5

What does Nn. subscapularis innervate?

Answer 5

m. subscapularis

Question 6

What does N. axillaris innervate?

Answer 6

• The true flexors of the shoulder: m. teres major, m. teres minor and m. deltoideus.
• M. cleidobrachialis (which used to be the clavicular part of the deltoideus).
• Supplies a branch to the shoulder joint capsule.
• Gives off a cutaneus branch: n. cutaneus antebrachii cranialis

Question 7

Route and connections of N. musculocutaneus

Answer 7

• From the brachial plexus runs towards the elbow joint on the caudo-medial surface of m. biceps brachii.
• Lies cranial to a. brachialis, n. medianus and n. ulnaris.
• Gives off a small branch at the shoulder joint to m. coracobrachialis.
• Distally to the shoulder, gives off r. muscularis proximalis to m. biceps brachii.
• Proximal to the elbow, gives off r. communicans to n. medianus.
• Distally gives off r. muscularis distalis to m. brachialis and a small branch to the elbow joint.
• Terminates as n. cutaneus antebrachii medialis.

Question 8

Route and connections of N. radialis

Answer 8

• From the brachial plexus, it runs over the tendinous insertion of m. latissimus dorsi.
• Enters between caput mediale and caput longum of m. triceps brachii.
• Divides into two branches: superficial and deep
• Continues disto-laterally on the caudal and lateral surfaces of m. brachialis.

Question 9

What does N. radialis innervate?

Answer 9

All extensors of the elbow, including the triceps and the anconeus

Question 10

Route and connections of R. superficialis of N. radialis

Answer 10

• Appears at the cranio-ventral edge of the triceps’ lateral head.
• Divides into two parts: lateralis and medialis
• The lateral branch gives off n. cutaneus antebrachii lateralis.

Question 11

What does R. superficialis of N. radialis innervate?

Answer 11

The skin on the cranio-lateral, cranial and cranio-medial aspects of the antebrachium

Question 12

Route and connections of R. profundus of N. radialis

Answer 12

• Runs beneath m. extensor carpi radialis and across the flexor surface of the elbow.
• Reaches the deep lateral aspect of the antebrachium by passing under m. supinator.

Question 13

What does R. profundus of N. radialis innervate?

Answer 13

• All the extensors of the crpus and digits, including m. extensor carpi ulnaris (which is functionally a flexor)
• M. brachioradialis.
• M. supinator.
• M. abductor digiti I longus.
• Sends a small branch to the elbow joint’s capsule.

Question 14

Route and connections of N. medianus

Answer 14

• Innitially bound to n. ulnaris by fascia, but separates in the proximal brachium.
• Proximal to the elbow recieves the r. communicans from n. musculocutaneus.
• Distal to the elbow, passes beneath m. pronator teres.
• Runs between the superficial and deep digital flexors, accompanied by a. mediana.

Question 15

What does N. medianus innervate?

Answer 15

• M. pronator teres.
• M. pronator quadratus.
• M. flexor carpi radialis.
• M. flexor digitorum superficialis.
• Parts of m. flexor digitorum profundus
• The elbow joint’s capsule.

Question 16

Route and connections of N. ulnaris

Answer 16

• Initially bound to the n. medianus by fascia, but separates from it in the proximal brachium.
• In the mid-brachium, gives off n. cutaneus antebrachii caudalis, which runs over the medial aspect of the olecranon and innervates the skin on the caudal antebrachium.
• Goes over the medial epicondyle.
• Runs between the superficial digital flexor and m. flexor carpi ulnaris caput ulnare.

Question 17

What does N. ulnaris innervate?

Answer 17

• M. flexor carpi ulnaris.
• Parts of the deep digital flexor.
• Small branch supplied to the elbow joint’s capsule.

Question 18

Origin of N. suprascapularis

Answer 18

C6-C7

Question 19

Origin of N. subscapularis

Answer 19

C6-C7

Question 20

Origin of N. axillaris

Answer 20

C6-C8

Question 21

Origin of N. musculocutaneus

Answer 21

C6-C8

Question 22

Origin of N. radialis

Answer 22

C6-T2

Question 23

Origin of N. medianus

Answer 23

C7-T1

Question 24

Origin of N. ulnaris

Answer 24

C8-T2