Nerves Of Orbit: Motor Nerve

Question 1

Oculomotor 3rd cranial nerve deep origin

Answer 1

Arises from midbrain by 2 nuclei:
1. Motor: lateral cell mass and central nucleus
2. Parasympathetic: edinger westphal nucleus

Question 2

Oculomotor 3rd cranial nerve superficial attachment and exit from brain

Answer 2

From anterior surface of midbrain in interpeduncular fossa

Question 3

Oculomotor 3rd cranial nerve course and end

Answer 3

1. Passes forwards between posterior cerebral and superior cerebellar artery
2. Pierces dura in front of decussation point between Tentorium free and attached borders
3. Passes in cavernous sinus lateral wall
4. Enter orbit via superficial orbital fissure by 2 divisions: superior and inferior

Question 4

Superior division supply (2)

Answer 4

2 muscles
1. Superior rectus muscle
2. Levator palpebrae muscle

Question 5

Inferior division supply (5)

Answer 5

1. Medial rectus muscle
2. Inferior rectus muscle
3. Inferior oblique muscle
   Parasympathetic fibers to:
4. Ciliary muscle
5. Sphincter pupillae muscle

Question 6

Applied anatomy: oculomotor nerve injury produces: (4)

Answer 6

1. Ptosis
2. Lateral squint
3. Pupil dilatation
4. Loss of accommodation

Question 7

Ptosis

Answer 7

(Upper eyelid dropping)
Due to Levator palpebrae paralysis

Question 8

Lateral squint

Answer 8

1. Due to medial rectus paralysis
2. Unopposed action of lateral rectus

Question 9

Lateral squint

Answer 9

1. Medial rectus paralysis
2. Unopposed action lateral rectus

Question 10

Pupil dilatation

Answer 10

Due to sphincter pupillae paralysis

Question 11

Loss of accommodation

Answer 11

Due to ciliary muscle paralysis