Lecture 21: Eye and Orbit I

Question 1

what is the vascular tunic

Answer 1

2nd/middle layer composed of the choroid, ciliary body, and iris

Question 1

what is the fibrous tunic

Answer 1

scleral- outermost layer
cornea

Question 2

what are the layers of the cornea in histology superficial to deep

Answer 2

epithelium- stratified squamous
Bowman’s membrane
collagen fibers
descement’s acellular
epithelium- squamous-columnar

Question 3

what are the layers of the sclera in histology superficial to deep

Answer 3

conjunctival epithelium- stratified squamous
episclera
stroma- thick collagen
suprachoroid lamina with melanocytes

Question 4

what muscle does the anterior layer of the iris contain and what does it do

Answer 4

constrictor pupillae, constricts the pupil

Question 5

is the constrictor pupillae controlled by PNS or SNS

Answer 5

parasympathetics

Question 6

what is the ciliary body

Answer 6

contains the ciliary muscle and changes lens shape for accommodation/focus

Question 7

is the ciliary body controlled by PNS or SNS

Answer 7

parasympathetics

Question 8

what layer of the eye contains blood vessels

Answer 8

choroid

Question 9

what layer in eye can the retina be seen histologically

Answer 9

choroidal layer

Question 10

what components make up the neural tunic

Answer 10

ora serrata, optic retina and posterior layer of the iris that contains the dilator pupillae muscle

Question 11

what is the junction between the retina and ciliary body

Answer 11

ora serrata

Question 12

what muscle lays in the posterior layer of the iris that dilates the pupil

Answer 12

dilator pupillae muscle

Question 13

is the dilator pupillae muscle controlled by SNS or PNS

Answer 13

sympathetics

Question 14

what is the canal of schlemn

Answer 14

drains approximately 2-3 microliters of aqueous humor per minute aqueous humor from the anterior chamber to the venous system

located on/in ciliary body

Question 15

what is the prelental region of the eye and what fluid is filled there

Answer 15

anterior and posterior chambers, filled with aqueous humor

Question 16

what is the retrolental region of the eye and what fluid is filled there

Answer 16

behind the lens, filled with vitreous fluid

Question 17

what is the pathway of light

Answer 17

cornea–> aqueous humor–> iris—> lens–> vitreous humor–> retina

Question 18

what structure makes up the majority of the neural tunic

Answer 18

retina

Question 19

what structure contains photosensitive rods and cones

Answer 19

retina

Question 20

what is the plexiform layer

Answer 20

synaptic connections between rods and cones to retinal ganglion neurons

Question 21

what is the nuclear layer

Answer 21

contains neuronal cell bodies of rods and cones

Question 22

what is the ganglion cell layer

Answer 22

axons leave the eye as the optic nerve

Question 23

what photoreceptor cell type has vision in light of low intensity and is predominate throughout the retina

Answer 23

rods

Question 24

what photoreceptor cell type has visual acuity and color vision

Answer 24

cones

Question 25

what are the two types of cones are present

Answer 25

short and medium wavelength

Question 26

what are the two color sensitivities in carnivores and artiodactyls

Answer 26

blue and green

Question 27

feline vs human cones for color vision

Answer 27

humans- 3 cones at higher density and provides higher acuity cats- 2 cones at much lower density provides higher sensitivity

Question 28

feline vs human rods for color vision

Answer 28

humans- rods provide spatial detail but darker image feline- rods at higher density provides higher sensitivity or brighter image

Question 29

what is the tapetum lucidum

Answer 29

functions as reflector which directs photons back through retina. provides additional chance for photoreceptors to capture these photons

Question 30

optic disk

Answer 30

location of exit for retinal ganglion cell axon

Question 31

optic nerve

Answer 31

formed from bundles of axons from retinal ganglion cells, surrounded by meninges and CSF in the subarchanoid space

Question 32

what is the result of increased intracranial pressure on the optic nerve

Answer 32

prevents normal blood flow through central retinal vessels clinical sign: papilledema or choked disk

Question 33

what keeps the lens capsule under tension

Answer 33

zonula fibers

Question 34

where do zonula fibers attach

Answer 34

ciliary body

Question 35

how does the lens change shape

Answer 35

change in tension of the suspensory ligaments

Question 36

what structure is located rostral to the zonula fibers

Answer 36

iris

Question 37

what kind of lens focuses on near objects

Answer 37

round lens

Question 38

what kind of lens focuses on distant objects

Answer 38

flattened lens

Question 39

constriction and relaxation of what muscle affects lens shape for changing focus

Answer 39

ciliary muscle

Question 40

describe the role of the ciliary muscle, zonula fibers and lens shape to see distant objects

Answer 40

ciliary muscle is relaxed, zonula fibers under tension, and lens is flattened/stretched thin to see distant objects

Question 41

describe the role of the ciliary muscles, zonula fibers and lens shape to see near objects

Answer 41

ciliary muscle is stimulated by parasympathetic innervation, causing muscle to contract, zonula fibers are relaxed, and in the absence of the tension from zonula fibers the lens becomes more circular to refract light for near objects

Question 42

what bony components form the wall of the orbit

Answer 42

frontal, lacrimal, zygomatic and palatine

Question 43

the lateral wall of the orbit is formed by what muscle

Answer 43

temporalis muscle

Question 44

what is the postorbital ligament

Answer 44

forms later portion of the orbit connects to frontal and zygomatic bones

Question 45

tarsal (Meibomian) glands

Answer 45

modified sebaceous glands that secrete an oily substance that acts to increase the viscosity of tears and decreases tear evaporation from the surface of the eye

Question 46

chalazion

Answer 46

inflammation/blockage of meibomian glands

Question 47

what kind of tumor disrupts normal irrigation of the cornea

Answer 47

meibomian gland tumors

Question 48

bulbar + palpebral conjunctiva=?

Answer 48

conjunctival sac- when eyes are closedw

Question 49

palpebral conjunctiva

Answer 49

when eyes are open create superior and inferior fornices

Question 50

what cell type is conjunctiva of eye

Answer 50

non-keratinized, stratified squamous epithelium with goblet cells

Question 51

primary infectious conjunctivitis can be caused by

Answer 51

bacteria, viruses, mycoplasma, fungi and parasites

Question 52

what structures anchor the eyelids and are the meeting points for upper and lower eyelids

Answer 52

lateral and medial palpebral canthi and commissures

Question 53

nicitating membrane/third eyelid

Answer 53

deep to the upper and low eyelids, drawn across the cornea and sclera, thought to provide both protective and moistening functions

Question 54

what muscle closes the eyelids

Answer 54

orbicularis oculi

Question 55

what cranial nerve innervates orbicularis oculi

Answer 55

CN VII- facial

Question 56

what muscle elevates the eyelids

Answer 56

levator palpebrae superiosis

Question 57

what cranial nerve innervates levator palpebrae superiosis

Answer 57

CN III- oculomotor

Question 58

lacrimal apparatus

Answer 58

controls tear production and drainage

Question 59

what secretes tears

Answer 59

lacrimal gland

Question 60

that lacrimal gland is under what kind of control

Answer 60

autonomic

Question 61

what cell produces the glycoprotein component of tear film

Answer 61

goblet cells of the conjunctivae

Question 62

tear summary: what gland produces tears, how do tarsal glands play a role and goblet cells

Answer 62

lacrimal glands secrete tears tarsal glands secrete oily substance that increases viscosity of tears and decreases its evaporation and goblet cells secrete the glycoprotein component of tear film