Nerves of the Thoracic Limb

Question 1

Nerves supplying the thoracic limb

(3 main sources)

Answer 1

• Dorsal branch of cranial nerve XI (aka accessory nerve)
• Ventral branches of thoracic & spinal nerves
• Brachial plexus (major contributor!!!)

Question 2

Dorsal Branch of Cranial Nerve XI

Answer 2

• Supplies trapezius m.
• Supplies parts of brachiocephalicus m.

Question 3

Ventral branches of

cervical spinal n. & thoracic spinal n.

Answer 3

• Supply omotransversarius m.
• Supply rhomboideus m.

Question 4

Brachial plexus

Answer 4

• Ventral branches of spinal n. & thoracic n.
• (+/-) C5
• C6= cranial spinal nerve 6
• C7= cranial spinal nerve 7
• C8 = cranial spinal nerve 8
• T1= thoracic spinal nerve 1
• T2 = thoracic spinal nerve 2
• Major contributor to thoracic limb
• Motor to skeletal muscle
• Cutaneous sensory from skin

Question 5

Suprascapular n.

Answer 5

• Supplies supraspinatus m. & infraspinatus m.
• Goes in front of the scapula
• Courses between supraspinatus m. & subscapularis m.

“Sweeny” in horses

Question 6

What causes “Sweeny” in horses?

Answer 6

• Damage to suprascapular n.
• Atrophy of supraspinatus m. & infraspinatus m.
• Shoulder pulls outward, slips out of the way
• No muscle backing

Question 7

Subscapular n.

Answer 7

• Courses into the subscapularis m.
• Sole innervation = subscapularis m.

Question 8

Which two nerves supply the subscapular m.?

Answer 8

• Axillary n.
• Subscapular n.

Question 9

Axillary n.

Answer 9

• Need to reflect deltoideus m. in order to see axillary n.
• Courses btwn subscapularis m. & teres major m.

Innervation:

• Parts of subscapularis m.
• Teres major m.
• Teres minor m. (Laterally)
• Deltoideus m. (Laterally)

Question 10

Musculocutaneous n.

Answer 10

• Courses alongside the biceps brachii m.

Innervation:

• Biceps brachii m. (obvious)
• Brachialis m. (deeper)
• Coracobrachialis m. (obvious)

Question 11

Radial n.

Answer 11

Major n. of the thoracic limb

Supplies all & any extensors of the forelimb (carpus, digits, etc)

Courses towards triceps brachii mm. & appears on the lateral side deep to the lateral head of the triceps brachii m.

Innervation:

• Triceps brachii m. (lateral, long, medial, accessory)
• Tensor fasciae antebrachii m.
• Anconeus m.
• Extensor carpi radialis m.
• Common digital extensor m.
• Lateral digital extensor m.
• Ulnaris lateralis m. (flexor not extensor) - exception
• Supinator m.
• abductor digit I longus m. (dogs)
• Extensor carpi obliquus m. (large animals)

Radial n. deep branch = motor

Radial n. superficial branches = sensory

Question 12

What would be the clinical implication of damage to the radial n.?

Answer 12

• The animal is unable to bear weight
• Radial n. paralysis
• Radial n. disease
• Elbow is dropped
• Digits knuckled onto their dorsal surface

Question 13

Median n.

Answer 13

• Courses along with the brachial a.
• Inntervation: pronator teres m.
• Flexor carpi radialis m.
• Superficial digital flexor m.
• Deep digital flexor m.- only the radial head
• Becomes sensory to the palmar paw

Question 14

Ulnar n.

Answer 14

• Courses along with the median n. & continues towards the olecranon

Inntervation:

• Flexor carpi ulnaris m.
• Deep digital flexor m.
• Caudal cutaneous antebrachial n. (sensory)
• Becomes sensory to the lateral paw (digit - large animals)

Need to move flexor carpi ulnaris to see how deep it goes

Question 15

Lateral thoracic n.

Answer 15

Inntervation: Cutaneous trunci m.

• Cut out when skinning

no clinical importance

Question 16

Long thoracic n.

Answer 16

Innervation: Serratus ventralis m.

• Surface
• No clinical importance

Question 17

Thoracodorsal n.

Answer 17

• Runs with thoracodorsal a.
• Innervation: thoracodorsal a.
• No clinical importance

Question 18

Cranial & caudal pectoral nn.

Answer 18

• Innervation: superficial and deep pectoral mm.
• Not clinically important