The orbit and peri orbital structures

Question 1

Shape of orbit

Answer 1

Pyramidal

Question 2

Orientation of orbit

Answer 2

Slight lateral and slightly outwards

Question 3

Does the orbit and peri orbital have gender and racial variations

Answer 3

Yes

Question 4

Inferior wall of the orbit

Answer 4

Zygomatic bone and maxilla

Question 5

What is the peri- orbital rim

Answer 5

A thick buttress of bone continuous with the facial buttresses

Question 6

What is the orbit filled with

Answer 6

Fluid
Full of soft tissue.
Not compressible

Question 7

Shape of medial wall

Answer 7

Rectangular

Question 8

Boundaries of medial wall

Answer 8

From anterior lacrimal crest (maxilla) to the apex
Lacrimal fossa - anterior
Lamina papyracea - posterior (paper thin plate of bone overlying the ethmoid sinus)

Question 9

What suture is at the margin of the medial wall and the roof of the orbit

Answer 9

Fronto- ethmoidal suture

Anterior and posterior ethmoid foramina

Question 10

What shape is the floor of the orbit

Answer 10

Triangular

Slopes upwards to merge with the medial wall at the maxilla - ethmoidal suture

Question 11

What separates the floor and the lateral wall

Answer 11

Inferior orbital fissure

Question 12

Significance of thin orbital floor

Answer 12

Protective mechanism - area of weakness - if the eye takes a blow there is a way pressure can be dissipated

Question 13

Boundaries of the floor of the orbit

Answer 13

Maxillary bone medially
Zygomatic bone laterally
Palatine bone posteriorly
Separates orbit from middle cranial fossa and temporal fossa

Question 14

Boundaries of the lateral wall

Answer 14

Zygomatic bone anteriorly and greater wing of sphenoid posteriorly

Question 15

Where are the zygomatic- temporal and zygomatic- facial nerves

Answer 15

Lateral wall

They pass through their respective foraminas

Question 16

What bone is the roof of the orbit formed from

Answer 16

Almost entirely frontal bone

Question 17

What is the roof formed from

Answer 17

Frontal bone and lesser wing of sphenoid

Question 18

What is housed in the infra temporal fossa

Answer 18

Temporalis muscle, maxillary artery and vein, buccal and temporals fat pads, communicates with the anterior part of IOF

Question 19

What is housed in the pterygopalatine fossa

Answer 19

Pterygopalatine ganglion, maxillary nerve and its branches, infra- orbital branch of the maxillary artery, communicates with the posterior part of the IOF

Question 20

Are the infra temporal fossa and pterygopalatine fossa intra or extra cranial

Answer 20

Extra cranial

Question 21

Function of orbital apex

Answer 21

Route of communication between the intra- cranial cavity and the orbit
Contains the optic canal and part of the SOF
Orbital apex syndrome

Question 22

Function of the annulus of Zinn

Answer 22

Divides the SOF into intra coronal and extra coronal spaces

Question 23

Superior orbital fissure

Answer 23

Gives origin to 4 rectus muscles
Transmits lacrimal nerve, frontal nerve, trochlear nerve, superior ophthalmic, abducens, nasociliary, inferior ophthalmic vein

Question 24

Which structures are not inside the annulus of zinc

Answer 24

Lacrimal, frontal and trochlear

Question 25

Fascial sheath

Answer 25

Eyeball lies in the orbit surrounded by a fascial sheath separating it from the orbital muscles and fat Eye is suspended in place by check ligaments and suspensory ligament of Lockwood

Question 26

Muscles of the eye

Answer 26

Superior rectus Inferior rectus Lateral rectus (VI) Medial rectus

Question 27

Ocular muscles

Answer 27

``` Superior rectus (III) Inferior rectus (III) Lateral rectus (VI) Medial rectus (III) Superior oblique (IV) - Down and lateral Inferior oblique (III) - NOT IN ANNULUS OF ZINN - Up and lateral ```

Question 28

Dacryoadenitis

Answer 28

Inflammation of the lacrimal glands

Question 29

Function of lacrimal gland

Answer 29

Produces tears which flow into canals leading to the lacrimal sac Tears drain through the nano- lacrimal duct into the inferior meatus of the nose