The eye and the orbit

Question 1

what bones make up the orbit?

Answer 1

frontal 
zygomatic 
maxillary 
lacrimal 
ethmoid 
sphenoid

Question 2

what do vessels and nerves which supply the orbit enter?

Answer 2

through foramina;
optic foramen
superior orbital fissure
inferior orbital fissure

Question 3

which structures pass through the optic foramen?

Answer 3

optic nerve

ophthalmic artery

Question 4

which structures pass through the superior orbital fissure?

Answer 4

ophthalmic vein
ophthalmic nerve (V1)
occulomotor nerve (III)
trochlear nerve (IV)
abducent nerve (VI)

Question 5

which structures pass through the inferior orbital fissure?

Answer 5

maxillary nerve (V2)

Question 6

what is the depth of the eyeball and the orbit?

Answer 6

eyeball = 24mm
orbit = 40mm

Question 7

apart from the eye, what mainly fills the orbit and why is this of clinical significance?

Answer 7

fat tissue
it is one of the last reserves of fat that we lose if we go into starvation
thats why if someone has sunken in eyeballs it means they have lost a lot of body fat

Question 8

what muscles control the eyelids and what are their functions?

Answer 8

orbicularis oculi - depresses/closes the eyelid

levator palpebrae superioris - elevates/ opens the eyelid

Question 9

what is the nerve supply of the levator palpebrae superioris?

Answer 9

CN III - Occulomotor nerve

Question 10

what helps the orbit eep its shape?

Answer 10

hard palate (tarsal palate)

Question 11

what is found within the tarsal/hard palate of the orbit and what is its function?

Answer 11

meibomian glands

helps prevent evaporation of the eyes tear film

Question 12

what type of glands are found are the eyelashes?

Answer 12

sebaceous glands

Question 13

describe the covering of the conjunctiva.

Answer 13

covers the inside of the eyelids and loops back over the sclera
continues to the fornix (conjunctival fornices)
stops at the corneosclera junction

Question 14

what part of the eye does the cornea and sclera cover?

Answer 14

cornea covers the anterior 1/6

sclera covers the posterior 5/6

Question 15

what is the functions of the iris, ciliary body and choroid?

Answer 15

iris controls diameter of the pupil and thus the amount of light that enters
the ciliary body suspends the lens and produces aqueous humour
the choroid supplies blood to the outer layers of the retina

Question 16

what is the function of the aqueous and venturous humour?

Answer 16

aqueous helps control intraocular pressure

venturous humour cushions the retina

Question 17

what are the different chambers of the anterior segment of the eye?

Answer 17

anterior chamber infant of the iris

posterior chamber behind the iris

Question 18

describe the drainage of the aqueous humour.

Answer 18

produced from ciliary body and secreted into posterior chamber
comes through the pupil until it reaches a corner - the angle of the anterior chamber
enters trabecular meshwork at this corneosclero junction
enters the schemms canal this drains into veins in the sclera - episclero veins

Question 19

wha are the functions of the intrinsic and extrinsic muscles of the eye?

Answer 19

intrinsic controls pupil diameter and helps alter lens curvature to enable us to see near objects
extrinsic muscles move the eye

Question 20

what are the intrinsic muscles and their nerve supply?

Answer 20

cilliaris muscle - occulomotor nerve III
constrictor pupillae - occulomotor nerve III
dilator pupillae - sympathetic plexus

Question 21

which muscle helps the us to see near objects and how?

Answer 21

cilliaris muscle

alters lens curvature

Question 22

what are the extrinsic muscles and their nerve supply?

Answer 22

superior, inferior, medial and lateral rectus 
superior and inferior oblique 
superior orbital = trochlear nerve IV
superior rectal = abducent nerve VI
everything else = Occulomotor nerve III

Question 23

which muscle originates from the lesser wing of the sphenoid (roof of orbit posteriorly) ?

Answer 23

superior oblique

Question 24

which muscle originates in the medical part of the orbit floor (anteriorly) ?

Answer 24

inferior oblique

Question 25

where do the extrinsic muscles attach to the sclera?

Answer 25

rectus muscles anteriorly | oblique muscles posteriorly

Question 26

what is the nerve innervation of the lacrimal gland?

Answer 26

parasympathetic facial nerve VII

Question 27

regarding the lacrimal gland, what happens when we close our eye lids?

Answer 27

constriction of the orbiculares oculists muscle creates a negative pressure opening up the lacrimal sac so the fluid is sucked into the punctae for drainage into the lacrimal duct

Question 28

where is the lacrimal gland situated?

Answer 28

anteriolaterally of the orbit

Question 29

before tears enter the lacrimal sac, what is it sucked through?

Answer 29

punctae found on the medial side of each eyelid

Question 30

what supplies motor and sensory innervation to the orbit?

Answer 30

motor ; - optic (CN II) - occulomotor (III) - trochlear (IV) - abducent (VI) sensory - ophthalmic V1 and maxillary V2 branches of the trigeminal

Question 31

what foramen does the sensory innervation of the orbit pass through?

Answer 31

opthalmic nerve V1 - superior orbital fissure | maxillary nerve V2 - inferior orbital fissure

Question 32

what are the main branches of the ophthalmic nerve?

Answer 32

nasociliary branch lacrimal branch frontal branch

Question 33

what does the maxillary branch V2 supply?

Answer 33

sensory innervation to the lower part / floor of the orbit and eyelids

Question 34

arterial supply is via what main artery?

Answer 34

opthalmic artery which is a main branch of the internal carotid

Question 35

the opthalmic artery goes through the orbital cavity via what foramen?

Answer 35

optic foramen

Question 36

what branches does the ophthalmic artery give off?

Answer 36

central retinal artery | short and long posterior ciliary arteries

Question 37

which arteries supply the choroid and which parts?

Answer 37

short posterior ciliary artery supplies the posterior part of choroid long posterior ciliary arteries supply anterior choroid, iris and ciliary body

Question 38

what is the blood supply of the retina?

Answer 38

the outer layer supplied by the choroid (which is supplied by the short and long posterior ciliary arteries) the inner layer supplied by the central retinal artery

Question 39

what does the central retinal artery travel within?

Answer 39

the substance of the optic nerve

Question 40

how can you view the blood supply of the eye?

Answer 40

through an ophthalmoscope (fund picture)

Question 41

what is the bright small circle found in the fund picture?

Answer 41

optic disc

Question 42

what do you find at the optic disc?

Answer 42

the start of the optic nerve | in the centre you find the central retinal artery and vein

Question 43

what is the name of the venous sinus which drainage of the orbit leads to?

Answer 43

cavernous sinus

Question 44

where are the venous sinuses situated?

Answer 44

between the layers of the dura matter

Question 45

what is the epithelium lining of the venous sinus?

Answer 45

squamous epithelium (endothelium)

Question 46

where do you find the cavernous sinus?

Answer 46

situated on either side of the body of the sphenoid bone where the pituitary fossa is

Question 47

what structures lie within/near the cavernous sinus?

Answer 47

within the sinus = internal carotid artery lying superior = optic nerve lying within the walls of the dura matter are the nerves which enter the orbit through the superior orbital fissure - III, IV, VI, opthalmic and optic nerves