Anatomy of orbit by sir azmat jehan ppt

Orbit everything

1. Orbit
By
KOMAL YASEEN

2. ORBIT
The orbital cavities are a pair of pear
shaped bony cavities that serve as a socket
for the eyeball and its related structures.
Each orbit on either side of the nose is part
of the skull. Several skulls bones take part
in the formation of each orbit.

3. The orbit is pyramidal in shape. The pyramid
is somewhat larger in front and narrows at
the back.
The approximate height, width and depth of a
human orbit is 35 –40 mm.
Ithasgotavolumeof29ml.

5. Salient features
Each orbital cavity is composed of 7 bones
Maxilla
Zygomatic
Sphenoid
Frontal

6. Ethmoid
Lacrimal
Palatine
Each orbit opens onto the face.
It presents 4 marginsat this broad opening.

7. Margins of the Orbit
At the orbital margin the orbit is wider than its
height.
The margins of the orbit are as follows:
Superior Orbital Margin:
It is the upper border.
It is contributed by the frontal bone.
It is the heaviest margin.

8. Inferior orbital margin:
It is the lower border.
It is formed by the Zygomatic and maxillary
bones.
It presents as a shaper edge.

9. Lateral border:
This is the outer border.
It is a strong thick bony edge.
Zygomatic and frontal bones take part in its
formation.

10. Medial border:
This is the inner border.
It is formed of the frontal and the maxillary
bones.
It is indistinct in its upper part and becomes
sharper in its lower part.

11. ORBITAL WALLS
Each orbit has a
roof
floor &
two sidewalls.

12. Roof:
The roof is made up of two bones:
The frontal bone
Sphenoid bone (lesser wing)
It consists of a very thin plate of
bone,
which separates the orbit from the
overlying brain.

13. In its outer part (anterolateral) there is a
shallow depression for the lacrimal gland
placed in the front or anterior part of the orbit.

14. Floor:
Three bones make up the floor i.e.
Zygomatic
Maxilla &
palatine bones.

15. Inner part of the floor at the back is relatively
weak and thin.
It separates the orbit from the maxillary sinus

16. Medial Wall:
This is the inner wall of the orbit.
It is formed of 4 bones.
Ethmoid
Maxilla
Lacrimal &
Sphenoid bone.

17. It is the thinnest wall.
Mainly formed of the Ethmoid bone.
Part of the ethmoid that forms the medial is
called Lamina papyrecea and is a paper
thin plate of bone.
It separates the orbit from the nasal cavity, the
ethmoidal &the sphenoidal sinuses.

18. Lateral Wall:
This is the outer wall of the orbit.
It is formed of 2 bones:
Zygomatic
Sphenoid(greaterwing)
Itisrelativelyastrongerwall.
Itprotectstheeyeball.


19. Since the eyeball occupies the anterior part of
orbit, only the posterior part of it gets
protection from the lateral wall
The anterior part of the eyeball therefore remains
vulnerable to trauma from the outer side.
It separates the orbit from the (temporal fossa)
and the brain.

21. IMPORTANT RELATIONS OF THE ORBIT
Brain:
Orbit is closely related to the brain in relation to its
roof and lateral wall
Para nasal sinuses:
Orbit is intimately connected to the paranasal
sinuses
Maxillalysinusviathefloor.

22. Ethmoidalandsphenoidalsinusviathemedial
wall.
Frontalsinusattheroof.
Anyinfectioncaneasilyspreadtotheorbitfrom
thesinuses.
Nasalcavityisrelatedtotheorbitatitsmedial
orinnerwall.

23. IMPORTANT OPENINGS OF THE ORBIT
Optic Foramen
Is an important opening at the back of the orbit.
It is present at the apex of the orbit.
It opens into the optic canal which contains the
optic nerve.
So the optic nerve ,ophthalmic artery,&meninges
enters the orbit through the optic foramen.

24. Superior orbital fissure:
Is a cleft at the back of the orbit.
It is present between the lateral wall and the roof
of the orbit.
a number of structures pass through this fissure
namely :
The 3rd cranial nerve -Oculomotor
The 4th cranial nerve –Trochlear

25. Branches of 5th cranial nerve.
 Lacrimal nerve.
 Frontal nerve
 Nasociliary nerve
6th cranial nerve –Abducent.
Superior ophthalmic vein.

26. Edges of this fissure give attachment to an
important ligament that gives rise to the
muscles of the eyeball.

27. Inferior orbital fissure:
This is an other cleft, which separates the lateral
wall and the floor
Important structures passing through it are:
Branches of the 5th nerve.(maxillary)
Zygomatic nerve.
Some veins and arteries.(inferior ophthalmic
vein,infra orbital artery).

28. CONTENTS OF THE ORBIT
Eyeball
Muscles
to move the eyeball
Nerves
to move the muscles.
to carry different sensations
Blood vessels

29. Fat
For padding purposes.
For smooth movements
Most of the Lacrimal Apparatus.

30. PARANASAL SINUSES
Are air filled cavities lined with mucous
membrane, within the skull bones
These cavities communicate with the nasal cavity,
through different openings:
Following bones contain these cavities:
Frontal bone -frontal sinus
Maxilla -maxillary sinus
Ethmoid -ethmoidal sinus

31. Sphenoid -sphenoidal sinus
The mucus from these cavities moves into the back
of the nose.
Their main function is to act as resonators for voice
and to reduce the weight of skull
Any infection in the PNS can cause referred pain to
the orbit and can be misleading.
Infection can easily reach the orbit from the PNS.