Lesson 29 - Neuroanatomy of the Neck and Forelimb

What is the length of the spinal cord in relation to the vertebral column?

shorter

What does the neural canal extend to in most cases?

5th coccygeal vertebra

How many vertebra and spinal cord segments do dogs have?

35 vertebrae, 36 spinal cord segments

How many vertebra and spinal cord segments do horses have?

41 vertebrae, 42 spinal cord segments

How many vertebra and spinal cord segments do bovine have?

36 vertebrae, 37 spinal cord segments

What are the five major segments of the spinal cord?

1. C1 - C5 (Cervical)

2. C6 - T2 (Cervico-thoracic)

3. T3 - L3 (Thoraco-lumbar)

4. L4 - S1 (Lumbo-sacral)

5. S2 - Cd5 (Sacro-caudal)

What is the conus medullaris?

terminal conical part of spinal cord

Where is the conus medullaris in dogs?

L6 or L7

Where is the conus medullaris in cats?

variably between L6 and S3

Where is the conus medullaris in horses?

S2

What is the filum terminale?

thin extension of the modified pia matter surrounded by dura matter

What is the cauda equina?

bundle of spinal nerves spinal nerves L6-Cd5 that continue caudally after spinal cord terminates

What nerves are included in the cauda equina?

sciatic (L6-S2) and pudendal (S1-S3) nerves

Where do spinal nerves lie in relation to their respective vertebra in the cervical region?

in front of the respective cervical vertebra

Where does the 8th spinal nerve exit the neural canal?

caudal to the 7th cervical vertebra

What regions of the spinal cord have an equal number of spinal cord segments and vertebrae?

thoracic, lumbar, sacral

Where do spinal nerves lie in relation to their respective vertebra from the thoracic region to the end of the spinal cord?

behind/caudal to the respective vertebra

Which segments of the spinal cord are shorter?

caudal lumbar (L5, L6, L7), sacral (S1, S2, S3), and caudal/coccygeal (Cd1 to Cd5)

What is a sulcus?

groove in the brain/spinal cord

What are the sulci on the surface of the spinal cord?

dorsal median, dorsal intermediate, dorsolateral, ventrolateral

Where is the dorsal intermediate sulcus found?

cervical and cranial thoracic spinal cord only

What extends from the dorsolateral and ventrolateral sulci?

dorsal rootlets and ventral rootlets

What structures are seen on the surface of the spinal cord?

sulci, dorsal median septum, ventral median fissure, central canal

Where is the grey matter located in the spinal cord?

center (dorsal and ventral horns)

What does grey matter consist of?

neuronal cell bodies, dendrites, mostly unmyelinated axons, unmyelinated interneurons and neuroglia, blood vessels

Where do the dorsal and ventral roots/rootlets come from?

respective horns

What is 1?

General Somatic afferent column - Somatic Sensory

What is 2?

General visceral afferent column - Visceral sensory

What is 3?

General visceral efferent column - Visceral motor

What is 4?

General somatic efferent column - Somatic motor (lower motor neurons)

What is 7?

central canal

Where is white matter located in the spinal cord?

surrounding grey matter

Where do sensory/afferent axons originate?

dorsal horn

Where do motor/efferent axons originate?

ventral horn

Where do sensory/afferent axons carry impuses?

cranially to cranial segments of the spinal cord and then to the brain

Where do motor/descending axons carry impulses?

caudally in the spinal cord

What are funiculi made of?

ascending (sensory) and descending (motor) nerve fibers

What are the funiculi in the spinal cord?

dorsal, lateral, ventral

What is a fasiculus?

funiculus fibers grouped by common origin, destination, and function (sensory and motor pathways)

What is 2?

fasciculus cuneatus (sensory tract)

What is 5?

dorsal spinocerebellar tract (sensory tract)

What is 10?

ventral corticospinal tract (motor tract)

What is 11?

vestibulospinal tract (motor tract)

What is a dermatome?

area of the skin innervated by afferent nerve fibers (sensory innervation) from a single spinal nerve

How are dermatomes organized in the neck and trunk?

segments

What are myotomes?

set of muscles innervated (motor innervation) by a specific, single spinal nerve

What are the cervical spinal nerves?

ventral and dorsal branches, phrenic nerve, and fifth, sixth, and seventh cervical nerves

What are the superficial veins of the neck?

external jugular, omobrachial, axillobrachial

What is 1?

accesory n.

What is 2?

omobrachial v.

What is 3?

axillobrachial v.

What is 4?

cephalic v.

What is the brachial plexus?

nerve network formed by the ventral branches of the spinal cord (sensory and motor innervation of the forelimb)

What kind of neurons are mostly present in the distal limb?

mostly sensory (loses motor)

What is 1?

C4

What is 2?

C5

What is 3?

C6

What is 4?

C7

What is 5?

C8

What is 6?

T1

What is 7?

T2

Where does the suprascapular n. originate?

C6-C7

Where does the musculocutaneous n. originate?

C6-C8

Where does the radial n. originate?

C6-T2

Where does the median n. originate?

C7-T1

Where does the ulnar n. originate?

C8-T2

Where does the lateral thoracic n. originate?

C8-T1

Where does the axillary n. originate?

C6-C8

What is 1?

suprascapular n.

What is 2?

musculocutaneous n.

What is 3?

median n.

What is 4?

axillary n.

What is 5?

radial n.

What is 6?

median and ulnar n.

What is 7 and 8?

ulnar n.

What does the suprascapular n. innervate?

supraspinatus, infraspinatus

What does the subscapular n. innervate?

subscapularis (one or more branches)

What does the musculocutaneous n. innervate?

coracobrachialis, biceps brachii, brachialis

What does the axillary n. innervate?

deltoideus, teres major, teres minor

What does the thoracodorsal n. innervate?

latissimus dorsi

What does the cranial pectoral n. innervate?

superficial pectoral muscles

What does the caudal pectoral n. innervate?

deep pectoral muscles

What does the radial n. innervate?

Triceps brachii (all heads), Tensor fasciae antebrachii, Anconeus, Extensors of the carpus and digits (Extensor carpi radialis, Common digital extensor, Lateral digital extensor, Ulnaris lateralis, Abductor digiti I longus, Supinator)

What does the median n. innervate?

Flexor carpi radialis, Pronator teres, Superficial digital flexor, Deep digital flexor (humeral, radial, ulnar heads), Pronator quadratus

What does the ulnar n. innervate?

Flexor carpi ulnaris (ulnar & humeral heads), Deep digital flexor (ulnar head), Interossei

What does the lateral thoracic n. innervate?

cutaneous trunci

What does the long thoracic n. innervate?

serratus ventralis thoracis

What are the nerves of the manus in the horse?

median and ulnar

What is the main innervation of the manus in the horse?

median n.

Where does the median n. divide into medial and lateral palmar nerves?

above the carpus

What does the ulnar nerve branch into above the carpus?

dorsal and palmar branches

Where does the median palmar n. lie?

between the interosseus muscle and deep flexor tendon

Where does the medial palmar n. go in the mid-metacarpus region?

sends a communicating branch obliquely and ventrolaterally to the lateral palmar n.

What does the medial palmar n. become just above the fetlock?

medial (palmar proper) digital n

Which branch of the median n. has ulnar n. contribution?

lateral palmar n.

What does the lateral palmar n. branch into in the metacarpal groove?

medial and palmar metacarpal nerves

What does the lateral palmar n. become just above the fetlock?

lateral palmar proper digital nerve

What is the dorsal aspect of the distal forelimb innervated by?

1. dorsal branch of the ulnar nerve

2. medial cutaneous antebrachial nerve (branch of musculocutaneous n.)

3. dorsal branches from medial and lateral (palmar proper) digital nn.

What is 1?

ulnar n.

What is 2?

palmar br. of ulnar n.