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Anatomy > Lecture 14 > Flashcards

Lecture 14 Flashcards

1
Q

WHat does the uvea consist of?

A

choroid, iris and ciliary body

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2
Q

three main functions of the limbus?

A
  1. nourish peripheral cornea
  2. outflow for aqueous humor
  3. corneal epithelium regeneration
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3
Q

what separates the AC from PC?

A

iris. AC in front, PC in back.

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4
Q

where is aqueous humor produced?

A

in ciliary body (bilayer of ciliary epithelium) secreted into PC travels to AC then to TM.

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5
Q

it is debated what the posterior chamber extends to, what two places could it be?

A

anterior of vitreous or extends to zonules.

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6
Q

in the anterior eye, what two arteries do we have? what is unique about these?

A

anterior ciliary arteries and long posterior ciliary arteries. both these anastomose at major circle of iris.

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7
Q

which arteries are superficial, which are deep? difference?

A

peripheral corneal arcades are superficial and episcleral vessels are deep. deep will NOT move when you move conjunctiva but superficial will.

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8
Q

which nerve innervates the cornea? which two branches does it form? both branches loose what once they enter cornea? what are the nerves called that pass from stroma to epithelium?

A

long ciliary nerves (branch of opthalamic therefore CV1).
stromal and epithelial.
myelin sheaths (just epithelial branch also looses schawnn cells).
ramus perforans.

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9
Q

what type of cells are located at the limbus? these cells are located at a spot in the limbus called?

A

stem cells therefore XYZ hypothesis applies here.

palisades of vogt

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10
Q

What changes would be seen in the epithelium at the limbus (compared to corneal epithelium)?

A

thicker/less uniform, increase in wing cells, basal cells smaller and more dense, BM more undulating therefore LESS TRANSPARENT.

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11
Q

What changes would occur in Bowmans membrane at the limbus (compared to cornea)?

A

STOPS at peripheral cornea, marks end of anterior cornea.

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12
Q

What changes would occur in the stroma at the limbus (compared to cornea)?

A

corneal stroma continuous with scleral stroma. loses regularity of lamellae, variation in fibre spacing and increase in fibre diameter therefore LESS TRANSPARENT.

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13
Q

What changes occur at Decemets membrane at the limbus (compared to cornea)?

A

DM STOPS at cornea therefore DM or BM end at peripheral cornea.

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14
Q

what structure is located at the end of Decemets membrane?

A

schwalbes ring.

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15
Q

Changes in endothelium at the limbus (compared to cornea)? modified endothelium forms what?

A

corneal endothelium continuous with limbus.

TM and lines the angle (we dont want endothelial cells in actual TM it can block path)

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16
Q

Which syndrome has entire endothelial layer present inside TM?

A

chandlers syndrome.

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17
Q

canal of schlemm found where? how wide is the canal? what is it lined with?.TM is made up of what? TM backs up onto what and attaches?

A 
corneoscleral junction, behind TM
.3 mm 
endothelial cells
mesh of collagen fibres. 
scleral spur (longitudinal muscle from CM also attaches here)
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18
Q

What are the three parts that make up the TM?

A
  1. uveal (inner meshwork, wide passages, not much resistance)
  2. corneoscleral (largest, external meshwork, forms flat sheets with many pores therefore high resistance of aqueous flow)
  3. Juxtacanalicular tissue
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19
Q

aqueous flow gets into canal of schelmm how?

A

aqueous moves into the endothelial cells lining schlemms. Giant vacoules (15um) transport most of the fluid into the canal (little is doen by active transport or passive) all drive by IOP pressure gradient.

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20
Q

How does aqueous get into venous blood?

A
  1. canal of schlemm or

2. uveoscleral outflow

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21
Q

how does aqueous get out of schlemms canal if it chooses this venous blood route?

A

25-35 collector channels in canal, aqueous can go through these and empty into deep scleral venous plexus OR into aqueous veins (which then drain to eqpiscleral and vortex veins).

22
Q

if aqueous chooses outlofw through uveoscleral drainage where does it go? what percent of aqueous takes this path? what is unique about this pathway compared to other?

A

ciliary plexus then ciliary muscle then suprachoroidal space then vortex and anterior ciliary veins.
5-35%
no resistance in this pathway

23
Q

What is the pressure gradient that exists between the eyeball and outer area?

A

IOP is greater than venous pressure.

24
Q

which layer of the ciliary bilayer epithelium makes the aqueous humor?

A

non pigmented layer.

25
Q

the ciliary body forms what shape and is how wide? where does it extend to?

A

triangular and is 6mm wide.

ora serratta.

26
Q

when the ciliary muscle contracts what happens?

A

zonules relax and this allows the lens to become more rounded and therefore allows for accommodation.

27
Q

what type of muscle is ciliary muscle? what are the three different ciliary muscles located in ciliary body?is ciliary muscle vascularized? what is it innervated by?

A

smooth muscle.
longitudinal (outermost), radial, circular (innermost)
highly vascularized
innervated by both parasympathetic and sympathetic.

28
Q

which parasympathetic nerve innervates the ciliary muscle? which sympathetic nerve innervates ciliary muscle?

A

oculomotor (also elastic stimulation, allows lens to pop back to original shape, CN3 causes accommodation)
1% of terminals (small amount, relaxes accommodation)

29
Q

which sensory nerve stimulates ciliary muscle?

A

CV1

30
Q

What are the three ciliary body functions? (HINT triple A).

A

Accommodation, absorption of light and aqueous humor formation.

31
Q

what are the three layers of the ciliary body?

A

pigmented and non pigmented epithelium
stroma
muscle (smooth)

32
Q

During development of the eye, the neural tube invaginates until it forms a double layered cup, the outer cup is what type of epithelium? inner? what do they each form?

A 
outer= pigmented and forms the RPE
inner= non pigmented and forms neural retina
33
Q

what developmental structure provides the developing lens with blood?

A

hyaloid fissure.

34
Q

what is the purpose of the bilayer in the epithelium?

A

create an aperature.

35
Q

What are some changes that occur in the unpigmented portion of the ciliary epithelium in older eyes? in pigmented portion?

A

thickening of BM, cells pull apart.

irregular basal ends.

36
Q

what type of junction are the pigmented and non pigmented epithelium layers of the ciliary body connected by? what does this form? what is between the cells in each layer?

A

tight junctions which forms a blood aqueous barrier

gap junctions.

37
Q

do tight junctions occur in the iris?

A

NO. there is NO barrier on the anterior surface of the iris.

38
Q

what three processes contribute to aqueous humor formation?

A
  1. diffusion of ions/molecules (passive)
  2. ultrafiltration of plasma into ciliary stroma from endothelium (passive)
  3. active secretion of Na+ into posterior chamber (requires energy)
39
Q

what are the two receptor types involved in production of aqueous humor? what type of receptors are both of these?

A

alpha 2 and beta 2. if beta 2 is blocked, aqueous production decreases. if alpha 2 is increased, aqueous production decreases. (one is stimulatory one is inhibitory).
adrenergic, reduces aqueous production through an adenylate cyclase cAMP pathway.

40
Q

adrenergic receptors ( under sympathetic control) affect smooth muscle tone and vascular tone in what structures?

A

iris, ciliary body and endothelial linings of pathways

41
Q

CHolinergic receptors are under what kind of control? located where? do they have affects on aqueous humor production?

A

parasympathetic control. located in iris and ciliary body. NO only sympathetic system does.

42
Q

what is the aqueous msotly made up of?

A

electrolytes, low MW compounds and some protein (little 200x less than blood, lost of ascorbate)

43
Q

the main source of aqueous humor is from where? what other areas contribute metabolites to the contents of the aqueous?

A

ciliary processes.

corneal endothelium, lens and iris contribute metabolites.

44
Q

what are the main functions of the iris?

A

illumination control
aperture control for focus
aberration control

45
Q

Iris is innervated by what?

A 
parasympathetic control (CN3): constriction via iris sphincter (via short posterior ciliary nerves)
sympathetic: dilation via iris dilator. (sympathetic fibres travel with internal carotid artery into head through cavernous sinus to innervate dilator muscle via long posterior ciliary nerves)
46
Q

what four blood vessels and veins provide blood to and from the choroid?

A
  1. long posterior ciliary arteries (2)
  2. short posterior ciliary arteries (10-20)
  3. choriocapillaries
  4. anterior ciliary arteries (7)
  5. vortex veins (4)
47
Q

functions of the choroid are?

A
  1. nutrition to outer retina
  2. waste product removal
  3. passage of nerves and vessels (between choroid and sclera)
  4. absorption of stray light (due to light absorption in in melanocytes)
  5. emmetropization
48
Q

the choroid allows for changes in emmetropization in chicks by doing what during hyperopic defocus? myopic?

A

hyperopic: thin choroid + increased growth
myopic: thick choroid + decreased growth

49
Q

pigment is found in what two places?

A

front: gives the eye color

pigmentary layer in pigment epithelium: pigment frill

50
Q

melanin absorbs light in what color region? therefore the presence of melanin makes the eye appear what color? the eye will appear blue if what?

A

blue region
brown
if no melanin

Anatomy (18 decks)

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