D18 - Motor cranial nerves

Question 1

List the motor cranial nerves

Answer 1

• III. n. oculomotorius
• IV. n. troclearis
• VI. n. abducent
• XI. n. accessorius
• XII. n. hypoglossi

Question 2

Cranial nerve III.

Answer 2

• N. oculomotorius

Origin:

• Nucl. parasympatheticus (visceral motor fibers)
• Nuc. motorius (somatic motor fibers)

Leaves the cranial cavity through:

• Fissura orbitalis
• Ru: for. orbirotundum

(shares a common dural sheath with n. opthalmichi and n. abducent before leaving the cranial cavity)

Division when entering the orbit:

• R. dorsalis
• ​R. ventralis

Motor innervation:

• R. dorsalis:
  
  • M. levator palpebrailis
  • M. rectus dorsalis
• R. ventralis:
  
  • M. rectus medialis
  • M. rectus ventralis
  • M. obliquus ventralis

Parasympathetic innervation:

• Travels with r. dorsalis + synapse in ggl.ciliare
• Post ggl. fibers to:
  
  • M. ciliaris (optic)
  • M. sphinter papillaris (light accomondation)

Sensory innervation:

• Some sensory fibers join V₁ → terminal ggl.

Question 3

Cranial nerve IV.

Answer 3

• N. trochlearis

Origin:

• Nucl. trochlearis

Leaves the cranial cavity through:

• Only nerve to leave brain at dorsal side, crosses to contralateral side at decussation n. trochlearium
• Penetrates dura mater at ventral fold of tentorium cerebelli
• Leaves the skull via:
  
  • For. rotundum
  • Eq: for. trochleare
  • Ru: for. orbirotundum​ ?

Motor innervation:

• M. obliquus dorsalis (of the eye)

Question 4

Cranial nerve VI.

Answer 4

• N. abducent

Origin:

• Motor nucleus of n. abducent

Leaves the cranial cavity through:

• Fissura orbitalis (with V₂, III. and IV)

Motor innervation:

• M. rectus bulbi lateralis (of the eyeball)
• M. retractor bulbi (of the eyeball)

Question 5

Cranial nerve XI

Answer 5

• N. accessorius
• Part of vagus group
• Parasympathetic? fibers from ggl. cervicale craniale

Origin:

• Caudal part of nucl ambiguus (ikke rostral???)
  
  • ​Medulla oblongata
  • Fibers leave XI to joint X
• Nucl. accessorius
  
  • ​Cervical part of spinal cord
  • Fibers leaves spinal cord at lateral aspect and combine in a trunk that rung along the cord to enter the skull via for. magnum

Leaves the cranial cavity through:

• For. jugulare (with the other nerves of the vagus group: IX, X

Branches:

• Divides ventral to ala atlantis:
  
  • R. dorsalis
  • R. ventralis

Motor innervation:

• R. dorsalis:
  
  • M. brachiocephalicum (ø m. cleidobrachialis)
  • M. omotransversarius
  • M. trapezius
• R. ventralis:
  
  • M. sternocephalicus

Question 6

Cranial nerve XII

Answer 6

• N. hypoglossus

Origin:

• Nucl. hypoglossus (of caudal medulla)

Leaves the cranial cavity through:

• Canalis n. hypoglossi

Branches:

• Passes rostral between X and XI to reach the tongue and branches into:
  
  • Rr. superficialis
  • Rr. profundus

Motor innervation:

• Extrinsic and intrinsic muscles of the tongue (n. hypoglossus is the only motor nerve to the tongue)

Horse:

• Passes through medial compartments of gutteral pouch
  
  • ​Runs parallell with tr. linguofacialis to radix linguae