Lecture 19 Content Flashcards
What makes up the Fibrous Tunic of the eye?
- Sclera
2. Cornea
describe the sclera?
Dense CT “white of the eye”
- attachment site for extrinsic eye muscles
- elastic/mechanical support for globe
Describe the cornea?
- modified sclera (1/6th of globe)
- avascular, several nerve endings
- transparent bulge @ anterior suface
- bulge refracts light before it hits lens
- all nutrients from air
What makes up the Vascular Tunic?
- Choroid
- ciliary body
- Iris
Describe the Choroid layer?
inner surface of globe (posterior)
- vascular = helps nourish retina
- black pigmentation absorbs stray light
Describe the cilary body?
composed of muscles and ligaments
- smooth muscles - radial and circular (sphinter-like) fibers
- suspensory “ligaments” of lens
Describe the Iris?
colored portion of the eye
- smooth muscles - radial and circular (sphincter like) fibers
- muscle contractions controls diameter of pupil (hole)
- separates the anterior cavity into ant/post chambers
What makes up the anterior cavity?
has 2 chambers anterior to the lens
- anterior chamber - anterior to the iris
- posterior chamber - posterior to the iris
- aqueous humor
describe the Aqueous humor?
fills anterior cavity
- produced by the ciliary process
- returned to blood supply via the canal of Schlemm
- helps control intra occulor pressure
What makes up the posterior cavity?
posterior to lens (aka vitreous chamber)
- lens to retina
- vitreous humor (gel-like) fills posterior cavity
- assist sclera in maintaining shape of eyeball
What is the suspensory ligaments?
barrier between ant/post. cavity
- composed of 3 membrane (fused)
- lens is sandwiched between between layers
What is Glucoma?
several different types
- circulation of aqueous humor is blocked
- increased pressure > damage to the optic nerve
- edema in cornea > cloudy/grey-green eye
- offten assoc. w/ high blood pressure (+/- family history
The neural tunic is composed of what?
RETINA
- posterior pigmented layer
- anterior pigmented layer
What does the Posterior pigmented layer of the Neural tunic do?
- dark pigment absorbs stray light
- supports anterior neural layer
What does the anterior “neural” layer do in the neural tunic?
Anterior Neural layer contains 9 layers
- neurons, neuroglia, and blood vessels
- ganglia = integration and preliminary processing
- 130 million photoreceptors in a circular sheet
What are the 2 photoreceptors in the eye?
Rods : dim light (light/dark) 125 million per eye
Cones: 6 million per eye - most in the fovea centralis
Describe cones in the eye?
- requires “high energy” - bright light
- cone receptors turned to specific wave-lengths
- absense of any one type of cone = color blindness
What does the Macula Lutea and the fovea centralis do?
- center of visual axis
- contains high concentration of cones
- spot of greatest resolution (sharpest focus)
What is the blind spot?
Point where point where optic nerve exits the globe
- point where blood vessels enter/exit the globe
- located very close to and just medial to the fovea
What is the blind spot?
Point where point where optic nerve exits the globe
- point where blood vessels enter/exit the globe
- located very close to and just medial to the fovea
Describe the globe of the eye and the retina?
formed as lateral diverticula of the diencephalon
- each diverticulum collapses to form eye cup
- retina this early in neural tube arrangement**
- retina subsequently appears to be installed backwards
Describe the globe of the eye and the retina?
formed as lateral diverticula of the diencephalon
- each diverticulum collapses to form eye cup
- retina this early in neural tube arrangement**
- retina subsequently appears to be installed backwards
What are some of the clinical implications/ mechanical limitations of the eye?
light receptors (rods and cones) pointing the wrong way
receptors buried behind 9 layers
Blind spot where axons and blood vessels leave globe’
Result of 70 % of the image is lost
ONLY SEE 30%
describe the pineal gland?
tied to light reception diurnal behavior patterns
- out-pocketing of the diencephalon
Describe the Iris and what CN is it associated with?
CN III
- complicated circular and radial muscles (antagonist)
- sympathetic simulation > dilation of pupil
- parpsympathetic simulation > contraction of pupil
= regulates the amount of light that asses to retina
describe the ciliary muscles? and what CN is it associated with?
- complicated internal ring of muscles
- contraction REDUCES tension of the suspensory ligament
- suspensory “ligaments” affect how the lens stretched
- shape of lens affects where the eye focuses
- CILIARY MUSCLES DO NOT PULL UPON SUSPENSORY LIG.
Describe the Lens?
- thick biconvex disc of specialized fibers
- orientation of fibers makes the lens transparent
- no Blood vessels
- suspended from sclera by suspensory ligaments
what is accommodation? and what does it do? close and far objects?
ability to focus
- requires change in lens shape - little or lens movement
close objects?
- ciliary muscles contract, slack on suspensory ligaments and lens BULDGE
Far objects?
- ciliary muscles relax, ligaments tighten and lens FLATTENS
what is presbyopia?
- lens becomes stiff with old age
- ability to change shape of lens slows
- refractive property of lens also change
- can’t focus on near objects = (far-sighted)
- lens is ridged
What are cataracts?
(abnormal lens)
- combo of structural/bio-mechanical problems
- lens becomes cloudy (less light passes to retina)
- focusing becomes “patchy” across retina
What does the levator palpebrae superioris do? and CN associated with it?
Lift upper eyelid (CN III)
What does the obicularis oculi do and CN associated with it?
closes both eye lids (CN VII)
What does lateral rectus do and what CN is associated with it?
lateral movement - abducens CN VI
What does medial rectus do and what CN is associated with it?
medial movement - oculomotor CN III
What does superior rectus do and what CN is associated with it?
superior movement - oculomotor CN III
What does inferior rectus do and what CN is associated with it?
Inferior movement - occulomotor - CNIII
What does Superior oblique do and what CN is associated with it?
inferior and abduction (laterally)
- Trochlear CN IV
What does inferior oblique do and what CN is associated with it?
superior and abduction (laterally)
- oculomotor (CN III)
What does the palpebrae do?
upper and lower eyelids
What does the Canthi do?
medial and lateral canthus (w/ caruncle)
What is the conjunctiva?
single layer (skin ) that covers anterior surface of eye - conjunctivitis = pink eye conjunctival inflammations
What is the lacrimal gland?
superolateral corner of orbit
- secretes teas that bathe conjunctiva and cornea
- wash, moisten, minimize friction
What is the lacrimal apparatus?
- tears are squeezed into medial canthus with each eye blink
- tears drain through (lacrimal puncta) into canaliculi
- lacrimal sac > nasolarimal duct > nasal cavity
what is the Trochlea used for?
sling of CT for superior oblique muscle
