The document describes the anatomy of the eye and orbit. It details the bones that make up the orbit, including the frontal, sphenoid, maxilla, palatine and zygomatic bones. It then discusses the layers of the eyeball, muscles of the eyelid and extraocular muscles. The document outlines the parasympathetic and sympathetic innervation of the eye as well as the blood supply and venous drainage of the orbit.

1. ANATOMY OF
THE EYE AND
ORBIT
REVISION

2. WHAT BONES MAKE
UP THE BOUNDARIES
OF THE ORBIT?
Wall Bones
Superior • Orbital plate of frontal
bone
• LW sphenoid
Inferior • Orbital surface of
maxilla
• Palatine bone
• Orbital surface of
zygomatic
Medial • Ethmoid (orbital plate)
• LW sphenoid
• Frontal bone
• Lacrimal bone
• Frontal process of
maxilla
Lateral (thickest) • Zygomatic
• GW sphenoid

3. ORBIT SURROUNDED
BY PARANASAL AIR-
FILLED SINUSES
 Air filled sinuses located within
the bones of the skull and face
 Functions:
 Lightening weight of the head
 Humidifying and heating inhaled
air
 Increasing resonance of speech
 Protect vital structures in injury
 Superior to the orbit- frontal
sinus
 Inferiorly- maxillary sinus
 Medially- ethmoid sinus

4. THE EYEBALL
 Has 3 layers:
 Fibrous outer layer:
 Sclera: dense, white, avascular, continuous with the cornea
 Vascular middle layer
 Choroid: pigmented, vascular, continuous with ciliary body and iris
 Ciliary body = muscular thickening that provides attachment for the lens.
Secretes aq humor
 Iris = on anterior surface of the lens. It is a thin contractile diaphragm
 Inner retina layer
 Light sensitive
 Sensory neural layer

5. THE PUPIL
 Two involuntary muscles control
the size of the pupil:
 Dilator pupillae- sympathetic
innervation (makes the pupil
larger)
 Sphincter pupillae-
parasympathetic

6. ACCOMMODATION
 Ciliary m. control the shape of the lens- which
enables the eye to focus (accommodation)
 To focus on near objects:
 Ciliary m. contract through parasympathetic
innervation
 Release tension on the zonal fibers
 Lens becomes rounder/ convex- increased
curvature shifts focal point closer to the eye

7. MUSCLES OF THE EYELID
 Levator palpebra superioris m.
 Only in the UPPER eyelid
 Raises the eyelid
 Innervation via CN3
 Inserts into the tarsus
 In companion with the LPS m. is a collection of SM
fibers = superior tarsal m.
 Raises the eyelid
 Innervation via the sympathetic fibers from superior
cervical ganglion
Thus, CN3 lesion/ sympathetic
lesion leads to ptosis – drooping
eyelid

8. MUSCLES OF THE EYELID
 Orbicularis Oris m.
 A sphincter muscle located in the upper and lower eyelids
 Palpebral part of the muscle close the eyelids during
blinking and sleep
 Orbital part: voluntary action- screws the eyes tightly shut
for protection
 Innervated by the zygomatic and temporal branches of CN7
 Damage to CN7  paralysis  eyelids don’t close fully +
eversion of the lower eyelid  drying + damage to cornea
 Also assists in pumping tears into nasolacrimal duct system

9. EXTRA-OCULAR MUSCLES
Muscle Attachements Actions Innervation
LPS From LW sphenoid to the superior tarsal
plate of upper eyelid
Elevates upper eyelid CN3
Superior rectus Superior part of the common tendinous
ring to the superior and anterior sclera
Elevation
Adduction
Medial rotation
CN3
Inferior rectus Inferior common tendinous ring to the
inferior and anterior sclera
Depression
Adduction
Lateral rotation
CN3
Medical rectus Medical part of common tendinous ring to
the anteromedial sclera
Adducts eyeball CN3
Lateral rectus Lateral part of the common tendinous ring
to the anterolateral sclera
Abducts CN4
Superior oblique Body of the sphenoid, attaches to the
sclera posterior to superior rectus
Depresses
Abducts
Medially rotates
CN4
Inferior oblique Anterior aspect of the orbital floor to the
sclera of the eye, posterior to lateral rectus
Elevates
Abducts
Laterally rotates
CN3
Located in the orbit, but extrinsic to the eyeball.
They act to control movements of the eyeball and
superior eyelid.

10. EYELIDS, CONJUNCTIVA
AND TEARS PROTECT THE
EYE
 Eyelids:
 Dense connective tissue
called Tarsus
 Embedded in tarsus = tarsal
glands
 Sebaceous secretions
which prevent tears from
evaporating
 Conjunctiva:
 Provides protection and
lubrication
 Contains blood vessels to combat
infection
 Consists of an epithelial layer
composed of stratified squamous
and stratified columnar epithelium
 Non-keratinized with
interspersed goblet cells
 Within the epithelial layer there
are BVs, fibrous tissue,
lymphatics, melanocytes, T/B
cells, Langerhan's cells,
accessory lacrimal glands
Note: the suspensory ligament is hammock
shaped thickening, enclosing the inferior
rectus m. it supports the eyeball

11. TEARS
Tears/ lacrimal fluid from lacrimal gland
produced by parasympathetic impulses from
CN7
Secreted through lacrimal ducts to surface of
conjunctiva
When eyelids blink, it pushes tears medially
over the cornea
Fluid containing foreign material pushes to
medial angle of the eye
Drains through lacrimal canaliculi into the
lacrimal sac
Nasolacrimal duct conveys the fluid to the
nasal cavity
Function of tears:
 Lubricate – basal tears
 Removing irritants – reflex
tears
 Aiding immune system

12. PARASYMPATHETIC
AUTONOMIC
INNERVATION OF THE
EYE
 Parasympathetic preganglionic
fibers for the eye are axons of cells
in the accessory oculomotor
nucleus.
 They run in the CN3 and exit in
the motor root of the ciliary
ganglion
 The axons of the ciliary root
ganglion are postganglionic
parasympathetic fibers which
reach the eye in the short ciliary
nerves and are distributed to the
sphincter pupillae, ciliary m. and
BVs

13. SYMPATHETIC
AUTONOMIC
INNERVATION OF THE
EYE
 Some of the filaments passing
through the superior orbital
fissure form the sympathetic root
of the ciliary ganglion
 Some pass through the ganglion
as short ciliary nerves.
 Other filaments join the
ophthalmic nerve or its nasociliary
branch and reach the eye in long
ciliary nerves that supply the
dilator pupillae
 Both long and short ciliary nerves
also contain afferents to the
cornea, iris and choroid

14. SYMPATHETIC
AUTONOMIC
INNERVATION OF THE
EYE
 Some of the fibers in the short
ciliary nerves pass through a
communicating ramus from the
ciliary ganglion to the
nasociliary nerve-
 This ramus is called the sensory
root of the ciliary ganglion
 Involved in reflex actions
 Other sympathetic fibers from
the internal carotid plexus reach
the eye through the ophthalmic
periarterial plexus

15. SUPERIOR ORBITAL
FISSURE AND OPTIC
CANAL
 ”What structures run through the
foramina of the orbit?”
 Superior orbital fissure: CN3,
4, 6 and sensory innervation to
the eye
 Optic canal: CN2 and
opothalmic a. and optic n.

16. BLOOD SUPPLY TO
THE ORBIT
 Ophthalmic a:
 First branch of the internal carotid,
runs anteriorly through the optic
canal along with optic n.
(inferolaterally)
 Branches supply all structures in
the orbit in addition to the nose,
face, meninges
 Central retinal a. is the first branch
of the ophthalmic a. which runs in
the dura mater inferior to the optic
n.
 Supplies the internal retinal layers
 Second branch is the lacrimal a.
which runs along the superior
edge of the lateral rectus m.
 Supplies the lacrimal gland, eyelids
and conjunctiva

17. VENOUS DRAINAGE
OF THE ORBIT
 Ophthalmic v.
 Superior and inferior subdivisions-
pass through the superior orbital
fissure and enter the cavernous
sinus
 Central retinal v.
 Drains blood from the capillaries
of the retina into the superior
ophthalmic v. or the cavernous
sinus directly