Boundaries and contents of the orbital cavity

1. The bony orbit & contents
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All the information, including the images and pics
collected from various sources is strictly for
teaching and helping the students in learning.
Dr. G. RAVINDRANATH MBBS; MS
PROFESSOR OF ANATOMY,
NRI INSTITUTE OF MEDICAL SCIENCES

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Learning objectives
1. Describe the boundaries of orbital cavity
2. Name the contents of the orbital cavity

3. The bony orbits
• Skeletal cavities located
on either side of the root of
the nose.
• Shape - quadrilateral
pyramid with its base at the
orbital opening & apex
along a posteromedially
directed axis at the optic
canal
• Each orbit has a roof,
floor, medial and lateral
walls.
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5. The bony orbits
• The medial walls lie
approximately 25 mm apart in
adults and are parallel.
• The angle between the
medial and lateral walls is
about 45°.
• Eyeball is located anteriorly within the orbit & thus occupies
only one fifth of the volume of the orbit , the remainder of the
cavity is filled with vessels and nerves that are contained within
and supported by orbital fat and connective tissue.
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6. The roof of the orbit
Formed by :
1. Orbital plate of the frontal
bone ,
2. Lesser wing of the sphenoid,
Anteromedially it displays a small
trochlear fovea, where the
cartilaginous trochlea (pulley) for
superior oblique is attached.
Anterolaterally there is a shallow
lacrimal fossa which houses the
orbital part of the lacrimal gland. Roof separates the orbital contents
and the brain in the anterior cranial
fossa.
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7. The roof of the orbit
• The roof slopes towards the
apex, joining the lesser wing
of the sphenoid. which
completes the roof.
• The optic canal lies between
the roots of the lesser wing
and is bounded medially by
the body of the sphenoid.
• The lateral wall and roof are
separated posteriorly by the
superior orbital fissure
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8. The medial wall of the orbit
Formed by:
1. Frontal process of the
maxilla
2. Lacrimal bone
3. Paper thin, rectangular
orbital plate (lamina
papyracea) of the ethmoid
bone
4. Body of the sphenoid
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9. The medial wall of the orbit
The orbital plate of the ethmoid bone separates
the middle and posterior ethmoidal air cells
from the orbit .
Posteriorly, it articulates with
the body of the sphenoid, which
forms the medial wall of the
orbit up to the apex.
Anteriorly the medial wall is
formed by the lacrimal bone
which contains a fossa for the
nasolacrimal sac
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10. The medial wall of the orbit
Fossa for the nasolacrimal sac
is limited in front by the anterior
lacrimal crest on the frontal
process of the maxilla and
behind by the posterior
lacrimal crest of the lacrimal
bone (to which the lacrimal part
of orbicularis oculi and lacrimal
fascia is attached).
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11. The medial wall of the orbit
Superiorly , medial wall articulates
with the medial edge of the orbital
plate of the frontal bone at a suture
which is interrupted by anterior and
posterior ethmoidal foramina.
A descending process of the lacrimal
bone at the lower end of the
posterior lacrimal crest contributes
to the formation of the upper part of
the nasolacrimal canal, which is
completed by the maxilla .
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12. The floor of the orbit
Formed by
1. orbital plate of the maxilla
2. orbital process of the palatine
bone.
The floor is thin and largely roofs
the maxillary sinus.
Anteriorly the floor curves and
continues into the lateral wall, but
posteriorly it is separated from the
lateral wall by the inferior orbital
fissure.
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13. The floor of the orbit
The medial lip of the inferior orbital
fissure, is notched by the infraorbital
groove which passes forwards and
sinks into the floor to become the
infraorbital canal, which opens on the
face at the infraorbital foramen.
Proportionally more orbital fractures
involve the floor, particularly in the
region of the infraorbital groove.
The classic ‘blowout fracture’ leaves
the orbital rim intact and typically
entraps soft tissue structures, leading
to diplopia, impaired ocular motility
and enophthalmos.
The inferior orbital fissure connects the
orbit posteriorly to the pterygopalatine
fossa, and more anteriorly to the
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N fratemporal fossa. 13

14. The lateral wall of the orbit
Formed by:
1. Frontal process of the
zygomatic bone (anteriorly),
2. Orbital surface of the greater
wing of sphenoid(posteriorly )
The bones meet at the
sphenozygomatic suture.
The lateral wall is the thickest wall
of the orbit.
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15. The lateral wall of the orbit
The lateral wall is continuous with the
floor anteriorly , but posteriorly it is
separated from the floor by the
inferior orbital fissure.
Similarly, the lateral wall and roof are
continuous anteriorly but are
separated posteriorly by the superior
orbital fissure, which lies between the
greater wing (below) and lesser wing
(above) of the sphenoid, and
communicates with the middle cranial
fossa.
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16. The lateral wall of the orbit
Laterally, the lateral wall separates the
orbit from the temporal and the
infratemporal fossa.
The zygomatic(lateral) surface of the
lateral wall shows the openings of two
minute canals :
1. Zygomaticofacial(near the junction
of the floor and lateral wall) and
2. Zygomaticotemporal (at a slightly
higher level than the former).
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17. The orbital tubercle of
Whitnall, to which the lateral
palpebral ligament,
the check ligament of lateral
rectus and the aponeurosis
of levator palpebrae are all
attached, lies just inside the
midpoint of the lateral
orbital margin.
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The lateral wall of the orbit

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Note the position of the common annular tendon(CAT) in the orbit

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Cavernous sinus

22. IDENTIFY……
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23. Contents of the orbit
The orbit contains the:
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3. Optic , oculomotor, trochlear and abducent nerves,
4. Branches of the ophthalmic and maxillary divisions of
the trigeminal nerve;
5. Ciliary parasympathetic ganglion;
6. Ophthalmic vessels;
7. Lacrimal apparatus.
1. Eyeball
2. Extraocular muscles;

24. THANK YOU
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