Ocular anatomy and histology part 1-3

what are the 3 gross parts of the eye

• orbit

• globe

• adnexa

what structures are a part of the anterior segment of the eye

• cornea

• anterior sclera

• anterior chamber

• posterior chamber

• iris

• iridocorneal angle

• ciliary body

• lens

what structures make up the posterior segment of the eye

• vitreous humor

• retina

• choroid

• optic nerve

• posterior sclera

what is the difference in orbit from a herbivore to a carnivore

a herbivores orbit makes a complete boney rim

why would it be easy for carnivores to get proptosis

because they have an incomplete bony rim

what other structure lies within the orbit

foramina for nerves and vessels

what muscles move the globe in the orbit

• rectus muscles

• oblique muscles

• retractor bulbi

the eye moves, up, down, left, right what muscle is causing that movement

the rectus muscles

the globe of the eye is rotated what muscle is causing that

oblique muscles

the globe is pulled back into the orbit what muscle is causing that

the retractor bulbi

what about the eyelid skin varies with species and breed

elasticity

what structure originates just outside the meibomian gland openeings

cilia

what structure opens at the mucocutaneous junction and secretes the lipid layer of the tear film

meibomian gland

lies between the cilia and meibomian glands and provides the eyelid margin with rigidity

tarsus

you watch a dog open its eyes what muscle is responsible for the elevating the upper eyelid

Levator palperbrae suparioris(LPS)

you watch a cat slowly blink at you what muscle is responsible for the closing the eyelids

Orbicularis oculi

what cranial nerves innervate the eyelid and what are their function

• cranial nerve 5- sensory

• cranial nerve 3,7 - motor

• autonomic - sympathetic nerve

what eyelid muscle is innervated with cranial nerve 3

levator palpebrae superioris

what eyelid muscle is innervated with cranial nerve 7

Orbicularis Oculi Muscle

what eyelid muscle is innervated with the autonomic nerve

Muller’s muscle

you scare a dog and see his eyes widen what muscle is responsible for this

Muller’s muscle

what structures anchor the eyelid into the eye socket

medial and lateral canthus ligaments

what is a mucocutaneous junction

a transition point between the mucous membrane (mucosa) and the skin

label the covered structures of the eyelid

A. Tarsus

B. meibomian gland

C. cilia

label the muscles of the eyelid

A. medial and lateral canthus ligaments

C. Orbicularis Oculi

E. levator palpebrae superioris

what is the conjunctiva

a mucous membrane of the eyelid

what are the parts of the conjunctiva

• palpebral

• bulbar

• fornix

• nictitans

if looking at a histology slide what will the conjunctiva look like

non keratinized stratified squamous epithelium with goblet cells

when looking at conjunctiva histology you see loose CT with leaky capillaries adjacent to the stratified squamous epithelium what is this area called

substantia propria

in inflamed conjunctiva you see fluid filling areas where there would be space, this would mean there was a loss of what?

subconjunctival space

what do the goblet cells of the conjunctiva produce

the mucus layer of the tear film

what is the most important function of the nictitating membrane

spreads tear film

what is the main function of the lacrimal apparatus

produce, distribute, and drain the precorneal tear film to maintain health of the ocular surface

what are the layers of the tear film

• lipid layer

• aqueous layer

• mucin layer

what structure produces the lipid layer of the tear film

meibomian gland

what structure produces the aqueous layer of the tear film

lacrimal and nictitating gland

what structure produces the mucin layer of the tear film

goblet cells

what is the flow of the lacrimal outflow apparatus

1. ocular puncta

2. canaliculi

3. lacrimal sac

4. nasolacrimal duct

5. nasal puncta

label the covered parts of the globe

1. cornea

2. iris

3. ciliary body

4. lens

5. sclera

6. choroid

7. retina

what are the 3 concentric tunics of the eye

1. fibrous

2. vascular

3. nervous

what are the parts of the fibrous tunic

• cornea

• sclera

what are the parts of the vascular tunic

• iris

• ciliary body

• choroid

what are the parts of the nervous tunic

• retina

• optic nerve

what are the functions of the cornea

• transmit light

• refract light

• protect internal contents

the anterior portion of the cornea is innervated by what cranial nerve

5

what are the 4 layers of the cornea

1. epithelium

2. stroma

3. descemet’s membrane

4. endothelium

what type and how thick is corneal epithelium

• non keratinized squamous epithelium

• 8-15 layers thick

how do microvilli aid the corneal epithelium

they stabilize the tear film

what is the turnover rate of the cornea epithelium

7 days

what are some important aspects of the stroma

• collagen is regularly arranged

• no blood vessels

• 78% water

• hydrophilic

in order to remain clear the corneal stoma must be

dehydrated

focal corneal edema is caused by

ulceration of corneal epithelium

diffuse corneal edema is caused by

damage to corneal endothelium

what is the function of the corneal endothelium

they actively pump fluid out of the corea

do corneal endothelial cells undergo mitosis

no

as corneal endothelial cells die and slough off how does the tissue heal itself

through enlargement and migration

what is the limbus of the eye

it is the junction between the corneal and scleral tissues

what is the difference between corneal and scleral collagen

scleral collagen is is nor regularly arranged