anterior segment Flashcards

1
Q

what are the three parts of the uvea

A
  • iris
  • ciliary body
  • choroid
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2
Q

what is the uvea

A
  • middle tunic
  • vacular, pigmented
  • derived from neuroectoderm, mesoderm
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3
Q

what is the iris

A
  • delicate vascular network
  • connective tissue, muscle, nerves
  • iris curvature mimics lens
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4
Q

what are the 4 structures of the iris

A
  • pupillary zone
  • iris collarette
  • ciliary zone
  • corpora nigra
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5
Q

iris muscle

A
  • smooth muscle in dogs and cats
  • controls pupil size, amount of light entering
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6
Q

sphincter iris muscle

A
  • constricts pupil
  • circular arrangement
  • parasympathetic, CN III
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7
Q

dilator iris muscle

A
  • dilates pupil
  • radial arrangement
  • sympathetic, CN V
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8
Q

ciliary body

A
  • smooth muscle
  • bi-layered epithelium
  • lens zonular attachment
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9
Q

what is the function of the ciliary body

A

aqueous humor production!

  • ultra-filtrate of plasma
  • fills anterior and posterior chamber
  • nutrition

aqueous humor drainage (angle)

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10
Q

what does ciliary muscle contraction do

A
  • releases tension on lense
  • fills anterior and posterior chamber
  • lens becomes “fatter”
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11
Q

uvea immune mechanism

A

it is immune-competent - behaves as accessory lymph node

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12
Q

what is the lens

A
  • transparent structure
  • focuses light rays on retina
  • sits between iris and vitreous
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13
Q

what does the lens compromise and what is it divided into

A
  • comprises capsule, anterior epithelium, lens fibers
  • divided into cortex and nucleus
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14
Q

what is the lens surrounded by? epithelium structure?

A
  • surrounded by elastic acellular capsule
  • single layer of epithelial cells on inner surface of anterior capsule
  • at equator, lens epithelial cells elongate into lens fibers, loose their nucleus and organelles
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15
Q

what are lens fibers

A
  • upright and inverted Y “sutures” can be seen in normal lens
  • new layers of lens fibers formed at equator throughout life
  • older fibers pushed toward center
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16
Q

the lense is supported at equator by ____

A

zonules

17
Q

zonules suspend lens from:

A

ciliary processes

18
Q

changing zonule tension changes lens:

A

refraction power

19
Q

lens metabolism

A
  • avascular: metabolic needs met by aqueous humor
  • disturbances in aqueous composition affects lens metabolism and transparency
20
Q

most gluclose in aqueous broken down anaerobically to lactic acid via:

A

hexokinase pathway

21
Q

what is excess glucose diverted to

A

sorbitol pathway - converted by aldose reductase to sorbitol

22
Q

nuclear sclerosis

A
  • normal aging process
  • characterized by a whittish-blue appearance of the nucleus
  • not opaque: fundus is visible, animal is visual
  • caused by change in protein composition and packing of lens fibers