Lecture 25: Eye and Orbit I Flashcards
3 tunics of the eye
Fibrous
Vascular
Neural
Fibrous tunic: 2 components, location
Sclera and cornea
Outermost layer
vascular tunic: position, components
2nd layer
Vascularized
Composed of choroid, ciliary body and iris
Layers of cornea from superficial to deep (5)
Stratified squamous epithelium (can regenerate)
Bowman’s membrane
Collage fibers
Descemet’s (acellular)
Stratified cuboidal epithelium (impermeable)
What happens to collagen fibers in cornea as they mature
Become crystalline
Clear for light to pass through
Layers of sclera from superficial to deep (4)
Stratified squamous conjunctival epithelium
Episclera with blood vessels
Stroma with thick collagen
Suprachoroid lamina with melanocytes
3 components of vascular tunic
Ciliary body
Choroid layer
Iris
Ciliary body
Contains ciliary muscle
Changes lens shape for accommodation/focus
Ciliary muscle is under what kind of control
Parasympathetic
Choroid layer contains
Blood vessels
Anterior layer of iris contains what muscle
Constrictor pupillae
Constrictor papillae is under what kind of control
Parasympathetic
Oral Serrata definition
Junction between retina and ciliary body
Components of neural tunic
Orra serrata
Optic retina
Dilator pupillae
Dilator pupillae under what kind of control
Sympathetic
Canal of schlemme function
Drains aqueous humor from anterior/prelental chamber to venous system
2 regions of lens
Prelental
Retrolental
Which region of lens is filled with aqueous humor
Prelental
Retrolental region of iris is filled with
Vitreous body = gel
Light pathway
Cornea —> aqueous humor —> iris —> lens —> vitreous body —> retina
2 types of photoreceptors
Rods
Cones
Rods
Very sensitive
Vision in light of low intensity predominate
Only 1 type of pigment
Cones: definition
Visual acuity and color vision
2 types
2 types of cones
Short and medium wavelength sensitivities (blue vs green)
Major of neural tunic is what structure
Retina
Retina contains (3)
Photosensitive rods
Cones
Specialized neurons
3 layers of specialized neurons in retina
Plexiform = synaptic contacts
Nuclear = neuronal cell bodies (nuclei)
Ganglion cell layer = axons leave eye as optic nerve
Tapetum lucidum
Part of choroid
Reflects photons back to retina to give retina another chance for photoreceptors to capture photons
Optic disk is the exit of
Optic nerve
Effect of increased intracranial pressure on optic nerve
Squeezes optic nerve
Prevents normal blood flow through central retinal vessels
Choked disk
Effect of constricting lens on light
Reduces light entering eye
Effect of changing shape of lens
Increases or reduces refraction of light for focusing
How does lens change shape during focus and accommodation
Constriction
Dilation
Change shape
What 4 structures allow lens to focus/accommodate
Ciliary muscle fibers
Dilator papillae
Constrictor papillae
Zonular fibers/suspensory ligaments
Zonular fibers functions (2)
Attach lens capsule to ciliary body
Can pull equator of eye to make eye more flat
Benefit of rounder lens
Focus on nearer object
Benefit of flatter lens
Focus on more distant objects
Parasympathetic stimulation of ciliary muscle
Contraction
Relationship of ciliary muscle and Zonular fibers
When ciliary muscle is contracted, Zonular fibers relax
When object is far away: effect on ciliary muscle, Zonular fibers, lens shape
Ciliary muscle relaxed
Zonular fibers under tension
Lens stretched thin to refract light for distant vision
When object is nearby: effect on ciliary muscle, zonular fibers, lens shape
Ciliary muscle contracted
Zonular fibers relax
Lens more spherical/thicker to refract light for near vision
**parasympathetic stimulation
2 muscles that control pupil diameter
Dilator papillae
Constrictor pupillary
Lateral wall of orbit formed by what muscle
Temporalis
Orbital septum
Connective tissue sheet around eyelids
Goes to wall of orbit
Tarsus: eyelid
Fibrous structure for rigidity
What is embedded in tarsal plates of eyelid
Tarsal/meibomian glands
Tarsal/meibomian glands: location, definition, functions
In tarsal plate
Modified sebaceous glands that secrete oily substance
Increases viscosity of tears, decreases tear evaporation from surface of eye
What nerve controls eyelid
Facial nerve
Chalazion
Inflammation/blockage of meibomian glands
Meibomian gland tumors
Growth of meibomian gland can disrupt normal irrigation of cornea
Gland still produces substance despite blockage
What 2 structures form conjunctival sac when eye is closed
Bulbar and palpebral conjunctiva
Inner eyelids and eye covered in __________
Conjunctiva
conjunctiva epithelial type
Non keratinized stratified squamous
WITH GOBLET CELLS
Bulbar vs palpebral conjunctiva
Bulbar = surface, eyes closed
Palpebral = eye opened
Conjunctivitis often affects which conjunctiva
Palpebral
Function of commissures and canthi
Anchor eyelids
Meetings sites of upper and lower eyelids
2 types of commissaries and canthi
Lateral and medial
Nictitating membrane aka
Third eyelid
Nictitiating membrane/3rd eyelid: location, function
Deep to upper and lower eyelids
Protection and moisten
2 holes in medial commissary
Superior and inferior punctum
Levator palpebrae superioris; function, nerve
Elevate eyelid
CNIII
Orbicularis oculi: function, nerve
Close eyelid
CN VII
Where does nasolacrimal gland drain to
Nasal cavity
Tear film: 2 components
Glycoprotein = produced by goblet cells of conjunctiva
Oil superficial layer = produced by tarsal glands