Anatomy of orbit by sir azmat jehan ppt

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.

 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.
 It has got a volume of 29 ml.

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

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

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.

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

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

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.

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

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.

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

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

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

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

 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.

Lateral Wall:
This is the outer wall of the orbit.
 It is formed of 2 bones:
 Zygomatic
 Sphenoid (greater wing)
 It is relatively a stronger wall.
 It protects the eyeball.


 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.

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
 Maxillaly sinus via the floor.

 Ethmoidal and sphenoidal sinus via the medial
wall.
 Frontal sinus at the roof.
Any infection can easily spread to the orbit from
the sinuses.
 Nasal cavity is related to the orbit at its medial
or inner wall.

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.

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

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

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

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 ).

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

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

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

 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.

Anatomy of orbit by sir azmat jehan ppt

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