anterior segment Flashcards
what are the three parts of the uvea
- iris
- ciliary body
- choroid
what is the uvea
- middle tunic
- vacular, pigmented
- derived from neuroectoderm, mesoderm
what is the iris
- delicate vascular network
- connective tissue, muscle, nerves
- iris curvature mimics lens
what are the 4 structures of the iris
- pupillary zone
- iris collarette
- ciliary zone
- corpora nigra
iris muscle
- smooth muscle in dogs and cats
- controls pupil size, amount of light entering
sphincter iris muscle
- constricts pupil
- circular arrangement
- parasympathetic, CN III
dilator iris muscle
- dilates pupil
- radial arrangement
- sympathetic, CN V
ciliary body
- smooth muscle
- bi-layered epithelium
- lens zonular attachment
what is the function of the ciliary body
aqueous humor production!
- ultra-filtrate of plasma
- fills anterior and posterior chamber
- nutrition
aqueous humor drainage (angle)
what does ciliary muscle contraction do
- releases tension on lense
- fills anterior and posterior chamber
- lens becomes “fatter”
uvea immune mechanism
it is immune-competent - behaves as accessory lymph node
what is the lens
- transparent structure
- focuses light rays on retina
- sits between iris and vitreous
what does the lens compromise and what is it divided into
- comprises capsule, anterior epithelium, lens fibers
- divided into cortex and nucleus
what is the lens surrounded by? epithelium structure?
- 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
what are lens fibers
- 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
the lense is supported at equator by ____
zonules
zonules suspend lens from:
ciliary processes
changing zonule tension changes lens:
refraction power
lens metabolism
- avascular: metabolic needs met by aqueous humor
- disturbances in aqueous composition affects lens metabolism and transparency
most gluclose in aqueous broken down anaerobically to lactic acid via:
hexokinase pathway
what is excess glucose diverted to
sorbitol pathway - converted by aldose reductase to sorbitol
nuclear sclerosis
- 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
