W21-L1: Contents of the Orbit Flashcards Preview

Matt's Block 06 - Neuro block > W21-L1: Contents of the Orbit > Flashcards

Flashcards in W21-L1: Contents of the Orbit Deck (52):
1

What forms the supra-orbital margin?

The frontal bone

2

What forms the infro-orbital margin?

Zygomatic bone laterally and maxialla medially

3

Which bones form the roof of the orbit?

Frontal bone, lesser
wing of sphenoid

4

Which bones form the floor of the orbit?

Maxilla,
zygomatic, palatine

5

Which bones form the lateral wall of the orbit?

Zygomatic, greater
wing of sphenoid

6

Which bones form the medial wall of the orbit?

Maxilla, lacrimal bone, ethmoid, body of sphenoid

7

Which bone of the orbit is often fractured?

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

8

What are the three layers of they eye?

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

9

How much of the eyeball does the sclera cover?

5/6ths

10

What is the function of the sclera?

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

11

Why is the sclera so tough?

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

12

What is the cornea?

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

13

What is the function of the cornea?

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

14

Why is the cornea optimum for vision?

Avascular and transparent

15

How many layers are there in the cornea?

Five

16

What is the epithelium layer in the cornea?

Mucus membrane

17

What is the stroma composed of in the cornea?

Collagen that is neatly arranged so its transparent

18

What is the role of the endothelium in cornea?

Controls water balance in the eye

19

How is the collagen arranged in the cornea?

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

20

What does the varying scleral opacity depend on?

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

21

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

It heals with no scar

22

What happens if you get stroma injury in the cornea?

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

23

What is the anterior chamber angle?

-Junction between iris and cornea
-Where aqueous humour drains out of eye.

24

What are the key structures in the anterior chamber angle?

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

25

What makes up the uvea?

Iris, ciliary body and choroid

26

What are some important structures in the ciliary body?

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)

27

What is the function of aqueous humour?

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

28

Where does the aqueous humour move around the eye?

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

29

What are zonules?

ligaments that attach between cililary processes and lens.

30

What does accommodation involve?

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

31

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

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

32

What causes expansion of lens?

Lack of tension due to contraction of ciliary muscles

33

Presbyopia

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

34

What is the iris?

The aperture of the eye

35

What muscles are in the iris?

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

36

What is the choroid?

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

37

Which is the most important layer of the choroid?

Choriocapillaris

38

What are the important parts of the retina?

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

39

What is the orra serrata?

Edge of the retina

40

What is special about the fovea?

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

41

What is the Lamina cribosa?

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

42

Why is the Lamina cribosa important?

In disease can damage ganglions around it

43

The orbit blood supply is from where?

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

44

What supplies the retina from the inner surface?

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

45

What are the ciliary arteries?

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

46

What is the path of the posterior ciliary arteries?

-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

47

What is the path of the anterior ciliary arteries?

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

48

What is the blood supply to the retina?

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

49

What are the eyelids?

transition zone between mucus and skin

50

What are the two muscles of the orbit?

-Orbicularis oculi
-Levator palpebrae superiosis

51

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

Elevates upper lid, innervated by CN III

52

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

Sphincter muscle that depresses upper lid, innervated by CN VII

Decks in Matt's Block 06 - Neuro block Class (48):