Contents of Orbit

Question 1

What bone forms the supraorbital margin?

Answer 1

the frontal bone

Question 2

What bones form the infraorbital margin?

Answer 2

zygomatic and maxilla

Question 3

What bones form the roof of the orbit?

Answer 3

frontal bone and the lesser wing of sphenoid

Question 4

What bones form the floor of the orbit?

Answer 4

maxilla, zygomatic and palatine

Question 5

What bones form the lateral wall of the orbit?

Answer 5

zygomatic, greater wing of sphenoid

Question 6

What bones form the medial wall of the orbit?

Answer 6

maxilla, lacrimal bone, ethmoid, body of sphenoid

Question 7

Which bones are at risk in a blow out fracture?

Answer 7

lacrimal bone and ethmoid bone

Question 8

What is the sclera?

Answer 8

the white of the eye

Question 9

What is the cornea?

Answer 9

the anterior 1/6th of the outer layer of the eye that is transparent and bends light

Question 10

Why is the sclera white and the cornea transparent when they are both made of collagen?

Answer 10

in the sclera the collagen is laid down in whirls for strength but in the cornea the collagen is laid down in bundles (lamellae) and within each lamellae all the fibrils are the same length and diameter and are evenly spaced and run in parallel

Question 11

What are the 5 histological layers of the cornea?

Answer 11

epithelium, bowman’s layer, stroma, descemet’s membrane, endothelium

Question 12

Why would you get a scar of the cornea?

Answer 12

if the stroma of the cornea was damaged and the order of the collagen was disrupted

Question 13

What is the anterior chamber angle?

Answer 13

the junction between the cornea and iris where aqueous humour drains out of the eye via the canal of schlemm

Question 14

What is the uvea?

Answer 14

the middle coat of the eye - contains the ciliary bodies, choroid and the iris

Question 15

What are the functions of the ciliary bodies?

Answer 15

formation of aqueous humour, tethers lens, accommodation

Question 16

Where is the aqueous humour formed?

Answer 16

by the two layers of ciliary epithelium on the ciliary processes that come off the ciliary bodies

Question 17

What are zonules?

Answer 17

ligaments that attach the ciliary body and the lens

Question 18

What happens when the ciliary muscle contracts?

Answer 18

the zonules which connect the ciliary body to the lens loose their tension which allows the lens to bulge and the eye can focus close up

Question 19

What innervates the ciliary muscle?

Answer 19

parasympathetic via CNIII

Question 20

What is presbyopia?

Answer 20

the loss of accommodation with age caused by reduction in flexibility of the lens

Question 21

What 2 muscles control the iris and what are they innervated by?

Answer 21

sphincter pupillae constricts the pupil and is controlled by parasympathetic innervation from CNIII, dilator pupillage dilates the pupil and is controlled by the sympathetic nervous system

Question 22

What is the choroid?

Answer 22

the layer underneath the retina which contains the blood vessels which supply the retina

Question 23

What is the fovea?

Answer 23

the area of the retina with the highest visual acuity - avascular, thin and with the highest density of cones

Question 24

What is the lamina cribosa?

Answer 24

the sclera that crosses the optic nerve and forms a sieve like structure through which the axons have to pass

Question 25

What artery supplies the blood to the orbit and what is it a branch of?

Answer 25

the opthalmic artery - the first branch of internal carotid

Question 26

What is the first branch of the opthalmic artery and what does it supply?

Answer 26

the central retinal artery - supplies the inner retina

Question 27

What blood vessels supply the photoreceptors in the outer retina via the choroid?

Answer 27

the long and short posterior ciliary arteries

Question 28

What blood vessels supply the anterior structures of the eye?

Answer 28

the anterior ciliary arteries

Question 29

What 2 muscles control the eyelids, what do they do and what are they innervated by?

Answer 29

orbicularis occuli closes the eyelid and is innervated by CNVII, legator palpebrae superioris opens the eyelids and is innervated by CNIII

Question 30

What are the 3 layers of the globe of the eye?

Answer 30

the outer layer is the sclera and cornea, the middle layer is the uvea and the inner layer is the retina and optic nerve