Anatomy: orbital cavity, eyelids, lacrimal apparatus, conjunctiva

Question 1

What shape is the orbital cavity?

Answer 1

Pyramidal

Apex points posteriorly and base anteriorly

Question 2

What bones of the skull make the roof of the orbital cavity?

Answer 2

Frontal and lesser wing of sphenoid

Question 3

What bones of the skull make up the floor of the orbit?

Answer 3

Maxilla, palatine and zygomatic

Question 4

What bones make up the medial wall of the orbit?

Answer 4

Ethmoid, maxilla, lacrimal, sphenoid

Question 5

What bones of the skull make up the lateral wall of the orbit?

Answer 5

Zygomatic, greater wing of sphenoid

Question 6

What are the 3 openings at the apex of the orbit called?

Answer 6

Superior orbital fissure
Inferior orbital fissure
Optic canal

Question 7

What paranasal air sinus is below the orbit?

Answer 7

Maxillary

Question 8

What paranasal air sinus is medial to the orbit?

Answer 8

Ethmoid

Question 9

Which parts of the orbital cavity are weakest?

Answer 9

Medial wall and floor (due to the air filled cavities)

Question 10

What is another term for eyelids?

Answer 10

Palpebrae

Question 11

What is the function of the eyelids?

Answer 11

Protect the eye when palpebral fissure closed

Keep cornea moist by covering it in a tear film

Question 12

The inner surface of the eyelid is lined by what?

Answer 12

Palpebral conjunctiva - this reflects on the eyeball and is continuous with the bulbar conjunctiva (overlays the anterior surface of eye)

Question 13

Movement of the eyelids occurs via what 2 muscles?

Answer 13

Obicularis occuli and levator palpebrae superioris

Question 14

What is LPS innervated by?

Answer 14

Occulomotor nerve

Question 15

What innervates obicularis occuli?

Answer 15

Facial nerve

Question 16

What makes up the fibrous skeleton of the eyelids?

Answer 16

Tarsal plates

Question 17

What glands do the tarsal plates contain?

Answer 17

Meibomian glands - modified sebaceous gland secreting lipid

Question 18

What are the contents of the orbital cavity?

Answer 18

Lacrimal apparatus 
Nerves and blood vessels 
Orbital fat 
Globe of eye 
Extra ocular muscles

Question 19

What is the orbital septum?

Answer 19

Thin sheet of fibrous tissue originating from orbital rim that separates intra orbital contents from eyelid fat and obicularis oculi

Question 20

Why is the orbital septum useful?

Answer 20

Prevents infection spreading from pre septal space to post septal space

Question 21

Meibomian glands open at the lid margin. Two other types of glands also open here, what are they called?

Answer 21

Glands of Moll

Glands of Zeiss

Question 22

What type of glands are glands of Moll?

Answer 22

Modified sweat glands

Question 23

What type of glands are glands of Zeiss?

Answer 23

Sebaceous glands

Question 24

Obstruction to the tarsal glands can lead to a painless swelling of the eyelid called…

Answer 24

A chalazion

Question 25

What is a stye?

Answer 25

An acute infection of a gland of Moll, Zeiss or the eyelash follicle

Question 26

What is another name for a stye?

Answer 26

Hordeolum externum

Question 27

What comprises the lacrimal apparatus?

Answer 27

Lacrimal glands, lacrimal ducts, lacrimal canaliculi

Question 28

Where is the lacrimal gland located?

Answer 28

In a fossa on the upper lateral part of the orbit

Question 29

Describe the route of the lacrimal fluid

Answer 29

From the lacrimal gland through the lacrimal ducts and into the conjunctival sac -> into lacrimal lake at medial angle of eye -> drains into lacrimal sac via lacrimal canaliculi then down the nasolacrimal duct

Question 30

Where does the nasolacrimal duct open into?

Answer 30

Nasal cavity - inferior meatus | It is then swallowed

Question 31

Is there any anastomotic pathways for the drainage of tears?

Answer 31

No - an obstruction will cause overflow

Question 32

What is tear overflow called?

Answer 32

Epiphora

Question 33

What is the conjunctiva and what does it cover?

Answer 33

A transparent mucous membrane that produces mucus and tears | Covers the white of the eye (sclera) and lines the inside of the eyelids (forming a conjunctival sac)

Question 34

Does the conjunctiva cover the cornea?

Answer 34

No

Question 35

Is the conjunctiva vascular ?

Answer 35

Yes

Question 36

What is the role of blinking?

Answer 36

Washes tear film across front of eye - rinsing and lubricating conjunctiva and cornea

Question 37

Why are tears needed?

Answer 37

Provide smooth surface Allows light rays to be refracted uniformly Lubrication to prevent friction Antibacterial properties

Question 38

What are the 3 components of the tear film?

Answer 38

Surface lipid layer - from Meibomian glands Middle aqueous layer - from lacrimal gland Inner mucus layer - from goblet cells of conjunctiva and epithelial cell surface

Question 39

Tears are rich in protein especially...

Answer 39

IgA