Orbit and Eyes

Question 1

What are the orbital margins?

Answer 1

supraorbital margin
-frontal bone

infraorbital margin

• zygomatic bone (laterally)
• maxilla (medially)

Question 2

what are the bones of the roof of the orbit?

Answer 2

frontal bone, lesser wing of sphenoid

Question 3

what are the bones of the floor of the orbit

Answer 3

maxilla, zygomatic, palatine

Question 4

lateral wall orbit bones?

Answer 4

zygomatic, greater wing of sphenoid

Question 5

medial wall of orbit bones?

Answer 5

lacrimal, ethmoid, maxilla, body of sphenoid

Question 6

which orbital bones are most commonly broken

Answer 6

medial wall bones, lacrimal and orbital plate of ethmoid are paper thin

Question 7

sclera?

Answer 7

white part of eyeball
5/6 of globe
maintains shape, offers resistance to internal & external forces
provides attachment of EOM

Question 8

what contributes to sclera strength?

Answer 8

whirling patter of collagen deposition

Question 9

what is the principal refracting component of the eye

Answer 9

cornea (it’s transparent)

Question 10

what are the 5 layers of the cornea

Answer 10

5 layers histologically including endothelium, descemets membrane, stroma (made of collagen), bowman’s layer, and epithelum

Question 11

why is cornea transparent

Answer 11

collagen fibrils are uniform in diameter and laid down in evenly spaced patttern, running parallel to eachother

Question 12

anterior chamber angle?

Answer 12

junction b/w iris and cornea. aqueous humour drains out of here.–>maintains size and pressure of eyeball

Question 13

what structures make up the anterior chamber angle?

Answer 13

corneal body, canal of schlemm, ciliary body, trabecular meshwork

Question 14

describe passage of aqueous humour?

Answer 14

from ciliary body –>anterior chamber–>canal of schlemm–>out of the eye into venous system

Question 15

uvea?

Answer 15

3 components: conjuctive, sclera, ciliary body
functions to improve retinal imaging by absorbing reflected light.
also its vessels perfuse the ciliary body and iris

Question 16

where is aqueous humour produced?

Answer 16

ciliary body (ciliary epithelium)

Question 17

function of ciliary body?

Answer 17

tethers lens (ciliary processes)
accomodation (ciliary muscle)
formation of aqueous humor (ciliary epithelium)

Question 18

what is the purpose of aqeous humor?

Answer 18

provides intraocular pressure

maintaining health of lens and cornea

Question 19

what is ocular accomodation?

Answer 19

Changes in contraction of the ciliary muscles alter the focal distance of the eye, causing nearer or farther images to come into focus on the retina.

ie. reflex to focusing on a near object and then a far away object.

depends on cranial nerve II and III.

Question 20

which structures are involved in accomodation?

Answer 20

ciliary muscle

zonules that attach to the lens

Question 21

what are zonules

Answer 21

ligaments that attach between ciliary processes and lens. are involved in accomodation.

Question 22

ciliary muscle receives Parasympathetic or Sympathetic innervation?

Answer 22

Parasympathetic!

non-voluntary (smooth muscle).

Question 23

what happens to ciliary muscle when looking at far away things?

Answer 23

ciliary muscle relaxes–>diameter of lens increases

–>zonules constrict

Question 24

what happens to ciliary muscle when looking at far away things?

Answer 24

ciliary muscle constricts—>diameter of lens decreases

–>zonules relax

Question 25

presbyopia?

Answer 25

loss of ability to perform accommodation with age.

due to reduction in flexibility of lens capsule and zonules.

Question 26

iris? muscles involved?

Answer 26

aperture of the eye.

1. sphincter pupillae: constricts pupil, innervated by PS.
2. dilator pupillae: dilates pupil, innervated by sympathetic NS.

Question 27

choroid

Answer 27

3 layers of blood vessels
-choriocapillaris is most important, sits just below retina

supplies nutrients to the retina.

Question 28

retina (5 components)

Answer 28

optic nerve/disc
fovea/foveola
macular
posterior pole
orro serrata

Question 29

fovea?

Answer 29

high visual acuity
avascular (gets nutrients from choroid)
no cones, all rods

foveal pits permit direct access to photoreceptors.

Question 30

what forms optic nerve

Answer 30

axons of ganglion cells as they exit the retina to pass visual information to higher cortical areas.

nerve is encased in a dural sheath. within that, 2/3 of the sclera forms a sheath around the nerve.
1/3 of sclera goes across the optic nerve, “lamina cribrosa”.

Question 31

lamina cribrosa?

Answer 31

band of dense CT.
provides extra strength where optic nerve enters the eye.

if pressure in the eye builds up , the LC bulks up and exerts pressure, causing loss of vision–>glaucoma

Question 32

vascular supply to the orbit?

Answer 32

ciliary arteries,

tributaries of ophthalmic artery,

central retinal artery

Question 33

what are the 3 ciliary arteries?

Answer 33

long posterior ciliary artery (pierce choroid and fans out to reach anterior portion),

short posterior ciliary artery (closest to optic nerve),

and anterior ciliary artery (runs along the eyeball to the anterior portion where it supplies the cornea).

Question 34

blood supply to retina?

Answer 34

dual supply.
central retinal artery supplies the inner retina.
posterior retinal artery supplies the outer retina (photoreceptors).

Question 35

muscles of the eyelid?

Answer 35

orbicularis oculi (sphincter muscle, closure, facial nerve, VII)
and levator palpebrae superiosis (striated muscle, opens, oculomotor III)

Question 36

lacrimal apparatus

Answer 36

lacrimal ducts and gland

nasolacrimal duct and sac