Anatomy

Question 1

What forms most of the roof of the orbit?

Answer 1

Orbital plate of the frontal bone

Question 2

Name the bones and bony features that make up the bony orbit

Answer 2

Orbital plate of the frontal bone, supraorbital notch/foramen, lacrimal bone, orbital plate of the ethmoid bone, maxilla, infraorbital canal, zygoma, sphenoid bone, optic canal, supraorbital fissure

Question 3

What does the supraorbital notch house?

Answer 3

The supraorbital nerve which is a branch of CN V1 (trigeminal)

Question 4

Describe the areas of the orbital rim

Answer 4

Superior, inferior, medial, and lateral orbital margins
Superior margin sits more anteriorly than the inferior margin and the medial margin sits more anteriorly than the lateral margin

Question 5

What gives the orbital rim is protective function?

Answer 5

It is very strong

The superior orbital margin sitting anteriorly to the inferior orbital margin

Question 6

What is an orbital blowout fracture?

Which parts of the orbit are most likely to be affected by this and why?

Answer 6

A fracture of the orbit in which the orbital rim remains in tact
The medial wall and the orbital floor are most likely to be fractured because they are very thin.
Floor of the orbit is more likely to fracture than the medial wall because the medial wall contains sinuses which shoot to dissipate the force.

Question 7

What is the most common bone affected in an orbital fracture?

Answer 7

Zygomatic bone

Question 8

Which nerve might be damaged in a floor of orbit fracture and why?

Answer 8

Infraorbital nerve - this is because it travels through the infraorbital canal which is part of the maxilla which makes up the floor of the orbit.

Question 9

What can happen if a fractured zygoma rotates medially?

Answer 9

The infraorbital neurovascular bundle can be damaged resulting in a general sensory deficit of the facial skin

Question 10

Describe the orbicularis oculi

Answer 10

Muscle of facial expression so supplied by the facial nerve
Acts as the sphincter of the eye
Is in 2 parts: in one part the fibres surround the eyelids to ‘screw up’ the eyes; the fibres of the other part are within the eyelids and are used in blinking

Question 11

What are the connective tissues in the eyelid?

Answer 11

Orbital septum, medial and lateral palpebral ligaments, superior and inferior tarsal plates, and the tendon of the lavatory palpebrae superioris muscle

Question 12

What is the palebral fissure?

Answer 12

The space between the upper and lower eyelids

Question 13

What is the orbital septum and what is its clinical importance?

Answer 13

A sheet of fascia attaching to the periphery of the orbital rim
It assists with preventing the spread of infection from superficial (periorbital cellulitis) to deep (orbital cellulitis)

Question 14

Describe the superior and inferior tarsal plates

Answer 14

Made of very tense connective tissue and give shape to the eyelids

Question 15

What do the medial and lateral palpebral ligaments do?

Answer 15

Attach eyelid to orbital rim

Question 16

What are the tarsal glands and where are they located?

Answer 16

Lipid secreting glands which are located on the inside of the eyelid: anterior to the palpebral conjunctiva and posterior to the tendon of the levator palpebrae superioris muscle and orbicularis oris

Question 17

what is the limbus?

Answer 17

junction between cornea and sclera - also known as corneoslceral junction

Question 18

what is the conjunctival fornix?

Answer 18

where the conjunctiva is reflected off the sclera and onto the internal aspect of the eyelid

Question 19

what is the lacrimal lake?

Answer 19

where tears gather before entering the puncta during blinking

Question 20

describe the puncta and the inferior lacrimal papilla

Answer 20

inferior lacrimal papilla is the swelling around the puncta

the puncta is the opening into the nasolacrimal duct

Question 21

what is the function of the conjunctiva?

Answer 21

the conjunctiva forms a defensive barrier to foreign bodies penetrating deep to it into the orbit

Question 22

does the cornea have its own blood supply?

Answer 22

no, it is avascular

Question 23

what is the nerve supply to the lacrimal gland?

Answer 23

CN VII - parasympathetic division

Question 24

what are the superior and inferior lacrimal canaliculi?

Answer 24

small canals which drain into the lacrimal sac

Question 25

what is the lacrimal sac?

Answer 25

the superior end of the nasolacrimal duct

Question 26

what is the function of the nasolacrimal duct?

Answer 26

drains tears from the lacrimal lake to the inferior meatus of the nasal cavity

Question 27

what are the 2 parts of the outer fibrous later?

Answer 27

the sclera and the cornea

Question 28

what are the functions of the sclera?

Answer 28

protective

attachment for extraocular muscles

Question 29

what is the function of the cornea?

Answer 29

provides about 2/3rds of the eye’s refractive power

Question 30

what is the uvea?

Answer 30

the vascular layer composed of 3 parts: the iris, the ciliary body and the choroid

Question 31

what is the function of the ciliary body?

Answer 31

control of the iris
control of the shape of the lens
secretion of aqueous humour

Question 32

what is the function of the choroid?

Answer 32

nutrition and gaseous exchange for the other layers

Question 33

what is the function of the inner retina?

Answer 33

photosensitive

composed of many layers

Question 34

What structures make up the anterior segment of the eye?

Answer 34

cornea, anterior chamber, iris, lens, ciliary body, posterior chamber

Question 35

what structures make up the posterior segment of the eye?

Answer 35

the posterior 2/3rds of the sclera, choroid and retina; and the vitreous body