The orbital cavity contains the eyeball and surrounding structures. It is pear shaped with seven bones forming its walls. Key structures discussed include the openings like the superior and inferior orbital fissures which connect the orbit to the brain. The document outlines the anatomy, dimensions, walls, openings and relations of the orbital cavity. It also discusses variations with age and surface anatomy landmarks.

1. Anatomy of orbital
cavity
Dr. Othman Al-Abbadi, M.D

2. Introduction
 The orbit is the cavity or socket of the skull, that
contain the eye ball and muscles ,nerve, vessels, fat
and lacrimal apparatus.
 Each cavity is pear shaped ,and its apex is directed
posteriorly ,medially ,and slightly upward.
 The medial wall runs antero-posterior parallel to
sagittal plane ,lateral wall diverges at angle 45degrees.
 Seven individual bones form the orbit (maxilla ,palatine
,zygomatic , sphenoid ,frontal ,ethmoid ,and lacrimal ).

3. O

4. Orbital dimensions
 Depth 42 mm along medial wall
 Depth 50 mm along lat wall
 Base :
 Width 40 mm
 Ht 35 mm
 Orbital index : (ht/width)X100
Racial variations
 Intraorbital width 25 mm
 Exrtraorbital width 100 mm
 Vol: 30 ml

5. Orbital margin
 Quadrilateral in shape with rounded corner.
 In adult : wider than it is high .
 supraorbital margin is formed by frontal bone .
(lat 2/3 sharp , med 1/3 rounded at the junction of two area
supraorbital notch or foramen for passage of supraorbital vessels
and nerve).
 infraorbital margin is formed (lat by zygomatic ,med by
maxilla).
 Lateral margin is the strongest part is formed (above by
frontal , below by zygomatic ).
 Medial margin is formed ( above by frontal , below by
lacrimal crest of maxilla),

6. Orbital margin

8. Walls of orbital cavity
 Walls are lined with periosteum ,and consist of roof ,floor
,medial, lateral wall.
 Apex is at medial end of superior orbital fissure.
 Roof
formed by orbital plate of frontal bone and small extent of lesser
wing of sphenoid posteriorly.
anterolaterally there is slight depression ( lacrimal fossa )for orbital
part of lacrimal gland .
Roof is thin and fragile ,in old age portion of roof may be absorbed.
Roof separates orbital cavity from anterior crainal fossa and frontal
lobe.

9.  Lateral wall
is the thickest wall.
anterior 1/3 is formed by zygomatic bone, separate orbit
from temporal fossa.
posterior 2/3 is formed by greater wing of sphenoid
,separate orbit from temperal lobe of brain.
it is continuous with roof anteriorly but seperated
posteriorly by superior orbital fissure .
marginal tubercle : a small prominence just
posterior to orbital margin on frontal process of zygoma ,
give attachment to aponeurosis of levator palpebrae
superioris ,lateral palpebral ligament ,lateral check
ligament .

10.  Floor
Formed largely by orbital plate of maxilla ,
orbital surface of zygomatic ,small orbital
process of palatine.
separate cavity from maxillary sinus.
Floor is continuous with lateral wall
anteriorly, but seperated posteriorly by
inferior orbital fissure .

11.  Medial wall
very thin wall, Formed by four bone from anterior to posterior :
frontal process of maxilla,
lacrimal bone,
Orbital plate of ethmoid (largest part, very thin separate cavity from
ethmoid sinus),
Small part of body of sphenoid.
Lacrimal groove: on anterior part of medial wall ,for lacrimal
sac , formed by lacrimal bone posterior ,frontal process of maxilla
anterior,bounded by lacrimal crests, continuous below with
nasolacrimal canal.

12. Opening in the cavity

13. Openings

14. Openings  Optic canal:
lies in the lesser wing of sphenoid.
related medially to body of sphenoid.
connect orbital cavity to middle cranial fossa .
transmit optic nerve, ophthalamic artery with surrounding sympathetic
plexus .
 Superior orbital fissure:
Lying between lesser and greater wing of sphenoid.
connect orbital cavity to middle crainal fossa .
widest part at its medial end.
midway on the lower edge of fissure is a small sharp spine give attachment
to common tendinous ring of origin for four rectus muscle.
transmit from lateral to medial (lacrimal nerve ,frontal nerve, trochlear nerve,
upper and lower division of oculmotor nerve , nasociliary nerve, abducent
nerve ,superior ophthalamic vein) .

15.  Inferior orbital fissure :
lies between greater wing of sphenoid and maxilla.
Connect pterygiopalatine and infratemperal fossa to orbital cavity .
transmit maxillary nerve, zygomatic nerve ,branches of pterygiopalatine ganglion,
inferior ophthalamic vein .
 Ethamoidal foramina:
lies in frontoethmoidal suture or in frontal bone.
anterior foramen open in anterior cranial fossa at lateral edge of cribriform plate
transmit anterior ethamoidal artery and nerve.
posterior foramen traverse ethamoidal bone transmit posterior ethamiodal artery
and nerve.
 Zygomaticofacial and zygomaticotemperal
foramen:
lies on the lateral wall of orbit.
zygomaticofacial foramen transmit zygomaticofacial nerve.
zygomaticotemperal foramen transmit zygomaticotemperal nerve.

17. Relation
 Superior
anteromedially : frontal air sinus.
anterior cranial fossa .
 inferior
maxillary air sinus
 Lateral
anteriorly : temperal fossa.
posteriorly :middle cranial fossa.
 Medially
nasal cavity ,ethmoidal sinus , sphenoid sinus.

18. Orbital periosteum( orbital fascia)
Periorbita: is the periosteum of the bone that form the wall
of orbit, loosely attached to bone .
At orbital margin, the periorbita is continuous with
periosteum on external surface of skull, ive attachment
to the orbital septum.
At lacrimal groove it splits to enclose lacrimal sac and
continue inferior to form periosteum of nasolacrimal
canal.
Posteriorly, around optic canal and medial end of superior
palpebral fissure, it thickens to form a fibrous ring
(common tendinous ring).
periorbita receive its sensory innervations from branch of
trigeminal nerve.

19. Orbital muscle
Muscle of Müller (Orbitalis muscle)
Thin layer of smooth muscle that bridge the
inferior orbital fissure .(vestigeal muscle)
Nerve supply : sympathetic
Function : unknown

20. Effect of age on orbital cavity
 At birth :
Relatively large and ossified margins
 Young children :
Look more lat than adult
Superior & inferior orbital fissure are wider become
narrowed by growth of greater wing of sphenoid .
Distance between the orbit are small and increases by
growth of frontal& ethamoidal sinuses
 Old age :
Bony absorption >>> holes in roof , med & lat walls

21. Surface Anatomy
 Superciliary ridges: prominent ridge above upper margin, deep to
ridge frontal sinus.
 Eyebrows
 Orbital margins ( frontal ,maxillary, zygomatic )
Frontozygomatic suture
Supraorbital notch
trochlea
Lat and med palpebral ligament
Ant lacrimal crest
Lac groove
Post lacrimal crest
Infraorbital foramen (5mmbelow lower margin)

22. Trauma to the orbit:
the orbit margin is very strong and not easily fractured .
Sever injury may cause fracture eg: automobile accident.
fracture of superior margin give symptom of superior oblique paralysis.
fracture of lateral margin >>>>depression & prominence of cheek.
comminuted fracture lower margin >>>blow out fracture.
Penetrating wound
surgical instrument, pointed metal object pierce thin roof of orbit
enter crainal cavity and frontal lobe .
Air sinuses
infection of sinus is commonest causes of orbital cellulitis