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It is pyramidal in shape, having a base, an apex & 4 walls.

Base: has 4 margins.

Apex: Optic canal.

4 Walls:Roof

1- Orbital plate of frontal b. 2-Lesser wing of sphenoid b.

Floor

1- Orbital surface of maxilla 2-Zygomatic bone

Orbital process of palatine b.

Medial wall

1- Lacrimal bone 2-Orbital plate of ethmoid b.Body ofsphenoid b.

Lateral wall

1- Zygomatic b. 2-Greater wing of sphenoid b

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The orbital cavity communicates with the:

Anterior cranial fossa via ant. and post. ethmoidalforamina

Middle cranial fossa viaoptic canal and the superior

orbital fissure Infratemporal fossa viainferior orbital fissure

Nasal cavity vianasolacrimal canal

At the meeting of the medial wall &the roof, there are:

Optic canal (optic nerve, ophthalmic artery & meninges)

Posterior ethmoidal foramen

Anterior ethmoidal foramen

There are 2 fissures related to lateral wall:

Superior orbital fissure (between lesser & greater wing of

sphenoid, pass through it: lacrimal, frontal, trochlear, superiordivision of oculomotor, nasociliary, inferior division ofoculomotor , abducent nerves & ophthalmic veins)

Inferior orbital fissure (between greater wing of sphenoid and

maxilla, passes through it: infra-orbital artery, maxillary nerve ,zygomatic nerve & emissary vein between inf. ophthalmic v. &

pterygoid plexus of veins.

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The eyeball.

The extra-ocular

m. Vessels:

Ophthalmic

artery &veins.

Nerves:

Sensory:

optic , Ophthalmic& its branches(lacrimal,frontal &nasociliary)

and zygomatic Motor: 3,4,6

Ciliary ganglion

Lacrimalapparatus

Orbital fat

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There are 4 recti ,2 obloquies & thelevator palpebrae superioris.

1-Levator palpebrae superioris

2- Superior rectus

3- Inferior rectus

4-Lateral rectus5-Medial rectus

6- Superior oblique

7-Inferior oblique

Intra-ocular: Dilator pupillae

Constrictor pupillae

Ciliary muscle

1 2

3

45

6

7

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Origin:

roof of the orbit in front of the

optic canal

Insertion :

superficial lamella: front of

superior tarsus & skin of upper

eyelid &deep lamella: upperborder of superior tarsus &

superior fornix of conjunctiva

Action:

elevation of upper eyelid andsup. fornix of conjunctiva

Nerve supply:

sup division of oculomotor n.&

smooth muscle by sympathetic

fibers from ( SCSG).

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Recti Muscles

Origin:common tendinous

ring, according to

their position (the

lateral rectus m.arises by 2 heads)

Insertion:

into the sclera, 6mm

from the limbus

(corneo-scleral

junction)

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Superior Rectus

Action:

Elevation , adduction

& intortion of eye. Nerve supply:

Superior division of

oculomotor.

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Inferior Rectus

Action:

depress, adduct &

extort the eye

Nerve supply: inferior

division of oculomotor

nerve.

Lateral rectus :

Abduct the eye &

supplied by abducent

nerveMedial rectus:

Adduct the eye &

supplied by inferior

division of oculomotor

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Superior Oblique origin:

Body of the sphenoid Insertion:

its tendon passes through thetrochlea, inserted into the sclerabehind the equator of eyeball

Action:

directs the cornea downwardsand laterally (depression.abduction and intortion)

Nerve Supply:Trochlear n.

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Inferior Oblique

Origin:

anterior part of the floor of the

orbit

Insertion: runs laterally and

upwards, inserted into the sclera

behind the equator of the eyeball

Action:

directs the cornea upwards and

laterally (depress, abduct & extortthe eye).

Nerve Supply:

inferior division of oculomotor n.

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S

OMR

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Action of the extraocular muscles About thevertical (X) axis the eye moves fromside-to-side Temporal displacements =Abduction Nasal displacements =Adduction

About the horizontal (Y) axis the eye movesup and down Downward displacements: Depression

Upward displacements: Elevation

About the anterior-posterior, or sagittal (Z) axis the eyerotates Temporal rotations of the superior cornea: Extorsions

Nasal rotations of the superior cornea: Intorsions

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The horizontal rod goingthrough the cornea represents

the visual axis. The vertical

rod with the arrow at the top

represents the vertical axis. As

the eye turns around the

vertical axis, the visual axis

sweeps along the horizontal .

Adduction & abduction

The rod going through thecornea represents the visual

axis. The horizontal rod with

the arrow represents the

horizontal axis. As the eye

turns around the horizontal

axis, the visual axis sweeps

along the vertical plane.

Elevation& depression

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The third plane of actionare Intortion andextortion refer to rotationaround the visual axis, asillustratedbelow. Intortion refers toa nasal rotation from the

12 o'clockposition. Extortion refersto a temporal rotationfrom the 12 o'clock

position. intortion or extortion of

the globe to keep theeyeballs level as the head

tilts.

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Anterior view

Posterior view

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Direct elevation:

Superior rectus &

inferior oblique.

Direct depression:

Inferior rectus &

superior oblique

Abduction or medialrotation:

Medial rectus, superior

and inferior recti.

Abduction or lateral

rotation:

Lateral rectus, superior

& inferior oblique

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M

L

L

M

Actions of Extra-Ocular M. Assuming That Each one Acting

Alone

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Muscle action action action testing

position

LR abduction abduction

MR adduction adduction

SR elevation intortion adduction up and out

IR depression extortion adduction down and out

IO extortion elevation abduction up and in

SO intortion depression abduction down and in

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Clinical Testing

Anatomical Action

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Innervation of the Extraocular Muscles

Medial, Inferior & Superior Rectus; InferiorOblique: Oculomotor nerve (III)

Superior Oblique:Trochlear nerve (IV)

N.B.: tendon of superior oblique passes throughthe trochlea

Lateral Rectus:Abducent nerve (VI)

N.B.: action of lateral rectus is abduction

(abducent)

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Intra-Ocular Muscles The muscles of the iris:

1- sphincter pupillae: circular in shape and are arranged aroundthe margin of the pupil.

Action: constrict the pupil in the presence of bright light.&during accomodation.

Nerve supply : parasympathetic

fibers from the oculomotor nerve(short ciliary branches of ciliary

ganglion.

2- dilator pupillae:

Radial fibers

Action:

Dilate the pupil in the presence

of light of low intensity & excessive

sympathetic stimuli as in fear.

Nerve supply : sympathetic fibers along long ciliary nerve.

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The Ciliary Muscle

Action:

Pulls the ciliary body forward.

Relax the suspensory ligament

and lens becomes more convex.

This increases the refractive

power of the lens.

Nerve supply:

Parasympathetic fibers from the

oculomotor after synaping in the

ciluiary ganglion.

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Ophthalmic artery:Branches:

Central a. of the retina

Muscular

Posterior ciliary

Anterior ciliary

Lacrimal

Supratrochlear

Supraorbital

Dorsal nasal anastomse

with facial artery.

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It is an end artery, so

thrombus of it leads to

blindness.

Branches:

Sup.&inf. Nasal

& sup.&inf. Temporal.

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Superior ophthalmic vein Inferior ophthalmic vein.

The 2 veins communicatewith facial vein anteriorly

& end posteriorly in thecavernous sinus.

The inf. Ophthalmic veincommunicate with pterygoid

plexus of veins by emissaryvein passing through the inf.orbital fissure.

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Sensory :

Optic nerve:

for vision.

Ophthalmic n.:

for general sensation.

Zygomatic n.

Motor: 3,4,6 nerves

Ciliary ganglion.

Sympathetic fibers:

from sup. Cervical

ganglion.

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Formed of axons of ganglion cells

of the retina & pierces the sclera

medial to the center of the eyeball Runs backwards and medially

and leaves the orbital cavity

through the optic canal.

Ends in the optic chiasma,

medial to the termination of ICA

The intraorbital part is sinuous,

to allow free movement of the eyeballStructures crossing optic n.

from lateral to medial: Ophthalmic artery

Nasociliary nerve

Superior ophthalmic vein

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the opthalmic artery runs below and lateral tothe optic nerve (and within its meningeal

sheath)The nerve is pierced by the central artery and

vein of the retina, 12 mm behind the eyeball

The nerve surrounded by meninges

&subarachnoid space contains CSF , So rise in CSF pressure will compress the

retinal veins & cause bulging of the optic disc(papilledema).

section of optic nerve leads to total blindnessof one eye.

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Branches:

Lacrimal:

Enters the orbit through the sup orbitalfissure (outside the common tendinous

ring)

Runs forwards and lateral, above the

lateral rectus receives a communication

from the zygomatico-temporal nerve

(which carries secretory fibers to thelacrimal gland)

Supplies the lacrimal gland

Gives palpebral branches to the lateralpart of upper eyelid

Frontal: Runs forwards beneath theroof, above the levator palpabrae

superioris &has 2 branches:

Supratrochlear & supraorbital

Nasociliary

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Nasociliary Nerve

Branches:

Communicating branch

to the ciliary ganglion

Long ciliary n. to dilatorpupillae m.

Posterior ethmoidal n.

Infratrochlear n.Anterior ethmoidal n.

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Position:

In the posterior part of the orbit on

the lateral side of the optic n.

Suspended from the nasociliary n

Roots: 1- parasympathetic:

Preganglionic parasympathetic via thenerve of the inf. oblique (oculomotor)

postganglionic short ciliary nerves

supply sphincter pupillae & ciliary

muscles.

2-Sympathetic:postganglionic from

the plexus around the int. carotid a.

3- Sensory: carry sensory fibersfrom

eyeball

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Divides into superior and

inferior divisions Both divisions enter the

orbit through the superiororbital fissure (inside thecommon tendinous ring)

The superior divisionsupplies: superior rectus

levator palpebrae superioris

The inferior divisionsupplies: Medial rectus

Inferior rectus

Inferior oblique

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The nerve to inferior oblique carries the parasympathetic

root to the ciliary ganglion

These parasympathetic fibers arise from the Edinger

Westphal nucleus in the midbrainThe postganglionic fibers supply the constrictor pupillae

and the ciliary muscle

In complete paralysis:

The eye cannot be moved downward, upward orinward.

External ( lateral) strabismus (squint).

Diplopia .

Drooping of the upper eyelid(ptosis).

dilated fixed pupil non reactive

to light.

loss of accomadation.

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Trochlear nerve

Arising fromposterior surface of the lowerlevel mid brain.

Supply superior oblique muscle.

Abd N

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Abducent Nerve Enter the eye inside the common tendinous

ring. Supply lateral rectus muscle.

Responsible for turning the eye laterally.

If cut leads to medial squint (strabismus)

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Lacrimal gland

Lacrimal ducts

Conjunctival sac

Lacrimal puncta

Lacrimal canaliculi

Lacrimal sac

Nasolacrimal duct:

open into inferior

meatus of the nose.

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Divided into orbital

&palpebralpartsby tendone of

levator palpebrae

superioris muscle.

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Lacrimal sac:It lies in the lacrimal

groove behind the medial

palpebral ligament.

Its upper end is blind

Its lower end is

continuous with the

nasolacrimal duct.

Nasolacrimal duct:

It end in the inferior

meatus of the nose.

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parasympatheticsupply:

Originates from:nucleus lacrimalis of facial nerve in pons

Then along nervus intermedius.

Preganglionicparasympathetic: Greater superficial petrosal

branch of facial nerveGreater petrosal nerve unit with deep petrosal nerve to form

nerve of pterygoid canal, which relay in pterygopalatine

ganglion then along zygomatic branch of maxillary nerve.

postganglionic parasympathetic: zygomaticotemporalbranch, then along lacrimal nerve to the gland.

Postganglionic sympathetic via deep petrosal from internal

carotid plexus.

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Orbital Fascia

Medial & lateral

check

ligaments &

suspensory

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References

Gray_s_Anatomy_Student_edition.part2.

Color_Netter_Atlas_of_Human_Anatomy.

Snell clinical anatomy for medical students 7

th

ed.

Clinically oriented anatomy 5th ed Keith Moore
http://rapidshare.com/files/78755044/Color_Netter_Atlas_of_Human_Anatomy.pdbhttp://rapidshare.com/files/78755044/Color_Netter_Atlas_of_Human_Anatomy.pdb

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13854254--Anatomy-of-orbit (1)