1. The Orbit, Orbital Contents and Cranial Nerves III, IV and VI

2. Lecture Objectives Describe the location of the orbit.
Make a list of structures making the orbit starting from orbital margin.
Define each component.
Describe openings into orbital cavity.
Define the orbital fascia.
Describe muscles of the orbit, their cone arrangement, origin, insertion, nerve supply and their function.
Describe the nerves of the orbit, their courses, important relations and their targets
Describe blood supply and lymph drainage of the orbit.

3. The Orbit: Orbital Margin

4. The Orbit: Orbital Cavity
Shape ..
Orientation ..
Walls ..

5. Openings into Orbital Cavity
Supraorbital notch (foramen)
Infraorbital groove, canal, & foramen
Nasolacrimal canal
Inferior & superior orbital fissures
Anterior & posterior ethmoidal foramina

6. Orbit: Content Eyelid Lacrimal apparatus Eyeball Fascia
Extraocular muscles
Nerves
Blood vessels
Fatty tissue

7. Eye: Fascia Covers the eye
Separate the eye from surrounding orbital fat
Facilitates movement of eye
Pierced by orbital muscles
Tubular sheath
Attaches to orbital walls
Medial & lateral check ligaments
Suspensory ligament of the eye

8. Eye: Muscles Extrinsic muscles Intrinsic muscles Superior rectus
Inferior rectus
Medial rectus
Lateral rectus
Superior oblique
trochlea
Inferior oblique
Intrinsic muscles
Ciliary m. ‐ parasympathetic
Constrictor pupillae of the iris
‐ parasympathetic
– Dilator pupillae of the iris ‐ sympathetic

9. Axes of Eyeball movements

10. Movements around transverse axis

11. Movements around vertical and A-P axes

12. Movements of Eyeball

14. Nerves of the Orbit

15. Nerves that Moves the Eyeball
Oculomotor (III)
Trochlear (IV)
Abducens (VI)

16. Oculomotor Nerve (III)
Mixed nerve; principally motor (GSE, GVE) (with proprioseptive)
Midbrain (anteriorly)
Cavernous sinus
Superior and inferior branches
Superior orbital fissure

17. Oculomotor Nerve Nuclei
Main motor nucleus (GSE)
Location
Relations
PAG, superior colliculus
Connections
Cortex, superior colliculus
Fibers course
Accessory parasympathetic nucleus (Edinger‐Westphal nucleus)(GVE)
Main motor nucleus
Pretectal nucleus

18. Pupillary Light Reflex

19. Oculomotor Nerve (III)
The superior branch
Superior rectus and levator palpebrae superioris mm.
The inferior branch
Medial rectus, inferior rectus, and inferior oblique mm.
Parasympathetic innervation via the ciliary ganglion to the intrinsic eye muscles
Major functions
Regulating movements of upper eyelid and eyeball
Adjustment of lens for near vision, and constriction of pupil

20. Oculomotor Nerve (III): Lesion
Ptosis (denervation of levator palpebrae)
External ophthalmoplegia: Eye look down & out (denervation of extraocular muscles)
Diplopia
Internal ophthalmoplegia: Dilated, fixed pupil & Paralysis of accommodation
Test
Asked to move the eye
Unable to move up, down, or medial
At rest looks down & lateral

21. Trochlear Nerve (IV)
Mixed nerve; primarily motor (GSE) (with proprioceptive)
Smallest of the cranial nerves
Midbrain*
Cavernous sinus
Superior orbital fissure
Innervate the superior oblique muscle
*Only one to arise from the posterior aspect of the brain stem
‐ Decussate and rotate around the brainstem

22. Trochlear Nerve (IV): Lesion
Difficulty to turn eye downward & laterally
Diplopia in looking downward

23. Trochlear Nerve Nucleus
Trochlear nerve nucleus (GSE)
Location
Relations
PAG, inferior colliculus, main oculomotor nerve nucleus
Connections
Cortex, superior colliculus
Fibers course

24. Abducens Nerve (VI)
Mixed nerve; primarily motor (GSE) (with proprioceptive)
Pons (anteriorly)
Cavernous sinus
Superior orbital fissure
Called abducens because it causes abduction of the eyeball (lateral rotation)
Innervates the lateral rectus muscle

25. Abducens Nerve (VI): Lesion
Nerve lesion causes internal strabismus & diplopia
Unable to turn eyeball laterally

26. Abducens Nerve Nucleus
Abducent nerve nucleus (GSE)
Location
Relations
4th ventricle
Colliculus facialis
Connections
Cortex, superior colliculus
Fibers course

27. Nerves of the Orbit Branches of ophthalmic nerve (V1) Frontal nerve
Superior orbital fissure
Frontal nerve
Scalp
Branches:
Supraorbital & Supratochlear nn.
Lacrimal nerve
Lateral part of upper eyelid
– Carry parasympathetic fibers to lacrimal gland via zygomaticotemporal nerve

28. Nerves of the Orbit Branches of ophthalmic nerve (V1)
Nasociliary nerve‐ Branches:
Comunicating branch to ciliary ganglion‐ sensory fibers from short ciliary nn.
Long ciliary nn.‐ carry sympathetic fibers (dilator pupillae m.)
Posterior ethmoidal n. (ethmoid & sphenoid sinuses)
Anterior ethmoidal n.
External nasal branch (tip of nose)
Infratrochlear n. (medial part of upper eyelid & part of nose)

30. Nerves of the Orbit

31. Orbit: Ophthalmic Artery
Optic canal
Branches of ophthalmic artery
Supraorbital a.
Supratrochlear a.
Central retinal a.
Ciliary aa. (short & long)
Ethmoidal aa. (anterior & posterior)
Lacrimal a.
Dorsal nasal a.

32. Orbit: Ophthalmic Veins
** No lymphatic vessels or nodes in orbit