When does the lens begin to differentiate from surface ectoderm?
When does the lens vesicle form?
When does the embryonic lens nucleus start development?
What is the function of the tunica vasculosa lentis?
Supports the development of the lens
When does the tunica vasculosa lentis disappear?
What provides nutrition to the lens after the tunica vasculosa lentis disappears?
aqueous and vitreous
What is a remnant of the hyaloid system?
persistent pupillary membrane
What is the general composition of the lens?
65% water; 35% proteins
What are the 3 major parts of the lens?
anterior & posterior capsule & epithelium
T/F: Lens epi is only found anteriorly.
What is the basement membrane of the lens epithelium?
What is the most important region of the lens epi? Why?
equatorial because it is responsible for the production of new lens fibers
Which direction is are new lens fibers pushed?
centrally to form nucleus and eventually the cortex
What is the region of alternating light and dark bands/lines seen in SLE?
Zones of discontinuity: layers/zones within the nucleus that have slightly different indicies of refraction; ripples in water
What is the region of clear or darker regions seen under the anterior lens capsule?
Zone of disjunction
What is the zone of disjunction composed of?
newest, youngest lens fibers
What are the characteristics of lens fibers?
Hexagonal in shape; lie in layers; go in anterior-posterior direction; interdigitate with adj fibers to form suture lines
What are suture lines?
initially seen in fetal nucleus; continually evolve into complex branching patterns as lens ages