W21-L1: Contents of the Orbit

Question 1

What forms the supra-orbital margin?

Answer 1

The frontal bone

Question 2

What forms the infro-orbital margin?

Answer 2

Zygomatic bone laterally and maxialla medially

Question 3

Which bones form the roof of the orbit?

Answer 3

Frontal bone, lesser

wing of sphenoid

Question 4

Which bones form the floor of the orbit?

Answer 4

Maxilla,

zygomatic, palatine

Question 5

Which bones form the lateral wall of the orbit?

Answer 5

Zygomatic, greater

wing of sphenoid

Question 6

Which bones form the medial wall of the orbit?

Answer 6

Maxilla, lacrimal bone, ethmoid, body of sphenoid

Question 7

Which bone of the orbit is often fractured?

Answer 7

Lacrimal and ethmoid bones as they are very thin, so medial wall

Question 8

What are the three layers of they eye?

Answer 8

Outermost: Sclera and cornea
Middle layer: Vascular (Uvea)
Inner layer: Neuronal

Question 9

How much of the eyeball does the sclera cover?

Answer 9

5/6ths

Question 10

What is the function of the sclera?

Answer 10

-Maintains the shape of the globe, offering resistance to
internal and external forces.
-Provides attachments for the EOMs

Question 11

Why is the sclera so tough?

Answer 11

The collagen and the arrangement which is not parallel, instead its in whirls

Question 12

What is the cornea?

Answer 12

Structure that is continuous with the sclera and covers the anterior 1/6th of the eye

Question 13

What is the function of the cornea?

Answer 13

Principal refracting component of
the eye (~60% of refraction)

Question 14

Why is the cornea optimum for vision?

Answer 14

Avascular and transparent

Question 15

How many layers are there in the cornea?

Answer 15

Five

Question 16

What is the epithelium layer in the cornea?

Answer 16

Mucus membrane

Question 17

What is the stroma composed of in the cornea?

Answer 17

Collagen that is neatly arranged so its transparent

Question 18

What is the role of the endothelium in cornea?

Answer 18

Controls water balance in the eye

Question 19

How is the collagen arranged in the cornea?

Answer 19

• Uniform in diameter and evenly spaced
• run parallel to each other in bundles called lamellae
• adjacent lamellae lie at angles to each other

Question 20

What does the varying scleral opacity depend on?

Answer 20

• Composition of the stroma
• Hydration
• Size and distribution of the collagen

Question 21

What happens if you lose only the epithelium in the cornea?

Answer 21

It heals with no scar

Question 22

What happens if you get stroma injury in the cornea?

Answer 22

Loss of ordered collage and transparency, a scar if in the cornea

Question 23

What is the anterior chamber angle?

Answer 23

• Junction between iris and cornea

- Where aqueous humour drains out of eye.

Question 24

What are the key structures in the anterior chamber angle?

Answer 24

• Cornea
• Trabecular meshwork
• Canal of Schlemm
• Ciliary body

Question 25

What makes up the uvea?

Answer 25

Iris, ciliary body and choroid

Question 26

What are some important structures in the ciliary body?

Answer 26

Ciliary processes (ciliary eptihelium) which form aqueous humour and form an attachment for ligaments of the lens Ciliary muscle which allows us to focus (accommodation)

Question 27

What is the function of aqueous humour?

Answer 27

- Important for maintaining the health of the lens and cornea. - Creates intraocular pressure.

Question 28

Where does the aqueous humour move around the eye?

Answer 28

Passes through pupil, and drains via anterior chamber angle into the venous supply.

Question 29

What are zonules?

Answer 29

ligaments that attach between cililary processes and lens.

Question 30

What does accommodation involve?

Answer 30

1. ciliary muscle | 2. Zonules that attach to lens.

Question 31

What is the most important fibres of the ciliary muscle and what innervates them?

Answer 31

Circularly fibres are the most important, they are innervated by parasympathetic fibres

Question 32

What causes expansion of lens?

Answer 32

Lack of tension due to contraction of ciliary muscles

Question 33

Presbyopia

Answer 33

Refers to the loss of accommodation with | age caused by reduction in flexibility in the lens capsule and zonules

Question 34

What is the iris?

Answer 34

The aperture of the eye

Question 35

What muscles are in the iris?

Answer 35

- Sphincter pupillae: constricts pupil: innervated by parasymp NS. - Dilator pupillae: dilates pupil: innervated by Sympathetic NS

Question 36

What is the choroid?

Answer 36

The three layers of the blood vessels underneath the retina that supplies it

Question 37

Which is the most important layer of the choroid?

Answer 37

Choriocapillaris

Question 38

What are the important parts of the retina?

Answer 38

- Optic nerve/optic disc - Fovea/foveola - Macular - Posterior pole - Orra serrata

Question 39

What is the orra serrata?

Answer 39

Edge of the retina

Question 40

What is special about the fovea?

Answer 40

High visual acuity, avascular, high density of cones and no rods

Question 41

What is the Lamina cribosa?

Answer 41

- Band of dense connective tissue. - Sieve-hole that transmit nerve fibres. - Collagen fibres from sclera. - 3-10 sheets of connective tissue.

Question 42

Why is the Lamina cribosa important?

Answer 42

In disease can damage ganglions around it

Question 43

The orbit blood supply is from where?

Answer 43

From the opthalamic artery which is the first branch of the internal carotid

Question 44

What supplies the retina from the inner surface?

Answer 44

Central retinal artery, first branch of opthalamic, pierces optic nerve and fans out over the retina

Question 45

What are the ciliary arteries?

Answer 45

- Long posterior ciliary artery - Short posterior ciliary artery - Anterior ciliary artery

Question 46

What is the path of the posterior ciliary arteries?

Answer 46

-posterior cilliary arteries pierce the globe around the optic nerve and travel in the choroid -if they travel short and feed head of optic nerve they are called short, if they travel round to the front of the eye they are long

Question 47

What is the path of the anterior ciliary arteries?

Answer 47

does not pierce the globe, runs forward and supplies anterior structures

Question 48

What is the blood supply to the retina?

Answer 48

Dual blood supply to retina: - Central retinal artery supplies the inner retina - Posterior ciliary artery supplies the outer retina (photoreceptors)

Question 49

What are the eyelids?

Answer 49

transition zone between mucus and skin

Question 50

What are the two muscles of the orbit?

Answer 50

- Orbicularis oculi | - Levator palpebrae superiosis

Question 51

What is the function of Levator palpebrae superiosis and what innervates it?

Answer 51

Elevates upper lid, innervated by CN III

Question 52

What is the function of Orbicularis Oculi and what innervates it?

Answer 52

Sphincter muscle that depresses upper lid, innervated by CN VII