Ophthalmology Anatomy, Physiology, and Embryology Flashcards
anatomy of the eye
- what are the sections? what structures are in each?
ANTERIOR SEGMENT
1. Anterior chamber
(in front of iris)
- cornea
- iris
- limbus
2. Posterior chamber
(behind iris)
- front of lens
- ciliary body
- sclera
<><><><>
POSTERIOR SEGMENT
- back of lens
- sclera
- choroid
- tapetum
- retina
<><><><>
- optic nerve
bones of the orbit?
- what animals have complete vs incomplete?
- Frontal
- Maxillary
- Lacrimal
- Zygomatic
<><> - Pterygoid
- Palatine
- Sphenoid
> these 3 Hidden under the zygomatic arch
<><><><>
Incomplete orbit - orbital ligament
- dogs, cats, pigs
<><><><>
Complete orbit - temporal bone
- most grazing animals (horse, oxen, sheep, goat)
nerves of the eye
- optic, oculomotor, trochlear, trigeminal, abducens (CN II, III, IV, V, VI)
muscles of the eye, innervations
Muscles attached to the globe via insertion into the sclera
Function: move the globe via innervation with cranial nerves
<><>
- Recti: dorsal/ventral/medial/lateral/dorsal oblique/ventral oblique
> Dorsal, medial, ventral and ventral oblique recti: CNIII
> Lateral rectus: CN VI
> Dorsal oblique: CN IV
> Retrobulbar muscles (cone): CN VI
blood supply to the eye
maxillary > ophthalmic > ciliary artery and vein
Eyelids and nasolacrimal system anatomy
Upper/lower eyelid: Cilia on upper eyelid
Exterior covered by skin
Meibomian glands located on palpebral margin
o Function: secrete meibum (lipid)
Interior covered by palpebral conjunctiva
o Function: conjunctival goblet cells secretes mucin in tear film
Medial canthus: inner corner where upper and lower eyelid meet
Lateral cantus: outer corner where upper and lower eyelid meet
Closure: done by obicularis muscle and CN VII
Opening: done by levator palpebral superioris muscle and CN III
o Function: protect eye, distribute tear film, flush away debris
where is the fornix?
- on the top, between bulbar and palpebral conjunctiva
- on the bottom, between bulbar conjunctiva and bulbar side of the third eyelid
third eyelid structure and function
Covered by bulbar conjunctiva on inner face (facing ocular globe)
<><>
Passive movement over cornea
o Function: protects eye
<><>
Contains cartilage and a lacrimal gland at its base
o Function: gland produces 30-40% of aqueous portion of tear film
<><>
Lymphoid nodules on bulbar conjunctiva
o Function: local immune system
Nasolacrimal system
- components of tears
- where they go
Tears have 3 components:
o Meibum (top layer): neutral oils, phospholipids
> Function: prevents evaporation, increases tear film stability
o Aqueous (middle layer): water with inorganic salts
> Function: contains nutrients and immunoglobulins
o Mucin (bottom layer): glycoproteins rich in sialomucin
> Function: adheres tear film to corneal epithelial cells
<><>
Tears accumulate in lacrimal lake (medial canthal area cranial to third eyelid)
Nasolacrimal system: lacrimal punctum in upper and lower eyelids with their associated canaliculi join into the duct that terminates at the nasal punctum
o Function: filter tears into upper & lower lacrimal puncta by capillary flow into the canaliculi and duct to exit at nasal punctum
Anatomy: Episcleral and Scleral blood vessels appearance
Conjunctival blood vessels
* fine
* haphazard
<><>
Scleral blood vessels
* robust
* ~straight
corneal epithelium structure and function
Corneal Epithelium
* Non-keratinized stratified epithelium
* Non-pigmented, avascular
* Lipophilic layer
* Water barrier
* Renews itself in 7 days
* 8-15 cell layers thick
* Heavily innervated (CN Vo)
* Mechanical barrier
Corneal stroma structure and function
- Parallel and highly organized collagen fiber
bundles made from keratocytes - =~90% of corneal thickness
- Fewer nerves (CN V)
- Avascular
- Hydrophilic in nature
- Retains fluorescein stain
corneal endothelium and Descemet’s membrane structure and function
Descemet’s Membrane
* Basement membrane
* Elastic
* Does not retain fluorescein stain
* Barrier
<><><><>
Endothelium
* Monolayer
* No mitosis
* Active metabolic pump > pumps out aqueous humour (i.e.: keeps the cornea transparent by keeping aqueous out)
what is the uvea
- the middle layer of the eye between the sclera part and the retina
- It has 3 parts: Iris, Ciliary body, and choroid
iris structure and function
Iris: anterior uvea
o Open anterior margin: no epithelial coverage (tight junctions)
> Gateway for cells, protein, fibrin to enter anterior chamber
o Double epithelial layer on posterior margin
o Muscles: Dilator and Sphincter (smooth muscles)
o Colarette: middle section of iris
o Function: regulates amount of light entering the eye