ORBIT & OCULAR ADNEXAE - The Orbit

Question 1

What are the bones in the roof of the orbit?

Answer 1

Frontal bone and lesser wing of sphenoid.

Question 2

What are the bones in the floor of the orbit?

Answer 2

Maxilla, Palatine, Zygomatic bones.

Question 3

What are the medial wall bones of the orbit?

Answer 3

Medial - MELS.
, Maxilla, Ethmoid, Lacrimal and Sphenoid bones.

Question 4

What are the lateral bones of the orbit?

Answer 4

Zygomatic and greater wing of sphenoid.

Question 5

How does the sphenoid bone form? How was it made embryologically?

Answer 5

From cartilaginous precursors which ossify.

Question 6

What are the parts of the sphenoid bone (4)

Answer 6

1. Body - contains sella turcica
2. Greater wing - contributes to facial skeleton
3. Lesser wing - separates anterior and middle cranial fossa
4. Pterygoid Process

Question 7

What are the main structures in the body of the sphenoid? (4)

Answer 7

1. Sphenoid sinuses -
2. Sella turcica - contains tuberculum sellae (anterior wall), hypophyseal fossa (deepest part where pituitary gland is located), dorsum sellae (posterior wall)
3. Chiasmatic groove - sulcus formed by optic chiasm
4. Clinoid processes (anterior and posterior) - serve as attachments for tentorium cerebelli

Question 8

What holes are found within the sphenoid bone (5)

Answer 8

1. Optic canal
2. SOF
3. Foramen rotundum
4. Foramen ovale
5. Foramen spinosum

Question 9

What does the greater wing of the sphenoid contribute to in terms of structures? (3)

Answer 9

1. Floor of middle cranial fossa
2. Lateral wall of the skull
3. Lateral wall of orbit.

Question 10

What does the lesser wing of the sphenoid contribute to in terms of structure?

Answer 10

1. Roof of the orbit
2. Lateral border of optic canal

Question 11

What do the pterygoid process contain? (2)

Answer 11

Medial pterygoid plate - supports opening of nasal cavity
Lateral pterygoid plate - site of origin of medial and lateral pterygoid muscles

Question 12

What does the temporal bone contribute to - the orbit or the skull?

Answer 12

The lower lateral walls of the skull. (does not form the orbit)

Question 13

What are the 5 components of the temporal bone?

Answer 13

1. Squamous
2. Zygomatic process
3. Tympanic
4. Styloid process
5. Petromastoid

Question 14

What does the squamous part of the temporal bone articulate with?

Answer 14

Anteriorly - sphenoid bone
Laterally - parietal bone

Question 15

Which muscle is connected to the zygomatic process/arch?

Answer 15

The masseter

Question 16

Which hole does the tympanic part of the temporal bone form?

Answer 16

external auditory meatus of the external ear.

Question 17

What attaches to the styloid process of the temporal bone?

Answer 17

stylomandibular ligament of TMJ.

Question 18

What does the petromastoid of the temporal bone contain? (2)

Answer 18

1. Mastoid process - site of attachment of sternocleidomastoid
2. Mastoid air cells - resovoir of air equalising pressure of middle ear in case of auditory tube dysfunction.

Question 19

What are the 3 parts of the ethmoid bone?

Answer 19

1. Cribiform plate (crista galli –> falx cerberi attachment)
2. Perpendicular plate
3. Ethmoidal air cells

Question 20

What is the supraorbital margin formed by in the orbit?

Answer 20

Frontal bone

Question 21

What is the infraorbital margin of the orbit formed by?

Answer 21

Zygomatic and maxilla.

Question 22

What is the volume of the orbit in cm2

Answer 22

30cm3

Question 23

What is the depth of the orbit in mm

Answer 23

40-50mm

Question 24

What does the orbital roof separates the orbit from?

Answer 24

The anteror cranial fossa

Question 25

What does the superior orbital rim contain?

Answer 25

A notch which transmits supraorbital nerve and vessels which supply the forehead.

Question 26

What structure is the largest part of the medial orbital wall?

Answer 26

The orbital plate of ethmoid - separates orbit from ethmoid sinuses

Question 27

Where is the frontoethmoidal suture line and what is its clinical significance?

Answer 27

Marks approximate level of ethmoidsal sinus roof - any dissection above this line should be avoided as it will expose the cranial cavity

Question 28

Where are the anterior and posterior ethmoidal foramina located?

Answer 28

behind medial orbital rim at junction of medial wall and roof

Question 29

Where is the lacrimal fossa located? What does it contain?

Answer 29

depression in the inferomedial orbital rim formed by maxillary and lacrimal bone.

Holds the lacrimal sac, tears from the sac drain through the nasolacrimal duct into the nasal cavity.

Question 30

What is the thickest wall of the orbit?

Answer 30

Lateral wall

Question 31

What is whitnall’s tubercle? Where is it located?

Answer 31

found on the zygomatic bone, 4mm behind lateral orbital rim and 1cm inferior to frontozygomatic suture

Question 32

What are the attachments to whitnall’s tubercle? (5)

Answer 32

THE 5 Ls

1. Lateral rectus check ligament
2. Lateral palpebral ligament
3. Lockwood susponsory ligament
4. Levator aponeurosis
5. Lacrimal gland fascia

WHITNALLS TUBERCLE AND LIGAMENT IS NOT THE SAME THING.

Question 33

Which structure weakens the orbital floor?

Answer 33

inferior orbital fissure

Question 34

What is the difference between the infraorbital groove and the infraorbital foramen?

Answer 34

A groove on the floor of the orbit that transmits the infraorbital nerve, artery, and vein. The groove continues forward into the maxilla as the infraorbital canal, which ends at the infraorbital foramen.