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What are the names of the three divisions the iris can be divided into based on its embryological derivation?
- Superficial mesenchymanl layer (anterior leaf)
- deep mesenchymal layer (posterior leaf)
- posterior retinal layer (retinal leaf)
What type of embryological tissue is the superficial mesenchymal layer (anterior leaf) of the iris derived from?
neural crest mesenchyme
What type of embryological tissue does the deep mesenchymal layer (posterior leaf) of the iris come from?
neural crest mesenchyme
Where is the superficial mesenchymal layer (anterior leaf) of the iris found?
the ciliary zone outside of collarette
Where is the deep mesenchymal layer (posterior leaf) of the iris found?
ciliary zone and pupillary zone
What portions of the developed iris are considered part of the superficial mesenchymal layer (anterior leaf) of the embryological iris?
- anterior border layer
- small amount of stroma in the ciliary zone
What is most of the iris stroma derived from?
deep mesenchymal layer (posterior leaf)
What is the iris sphincter muscle derived from?
anterior iris epithelium (ectoderm layer)
Where are the superficial and deep mesenchymal layers of hte iris derived?
What is the posterior retinal layer of the iris made from? (embryologically)
- neuroectodermal epithelial cells
- the optic cup
What is a coloboma?
- Two types:
- iris, where the fetal fissure fails to close at the iris
- retinal coloboma, where fetal fissure fails to close posteriorly (closer to optic nerve)
Name the steps of the development of the sphincter muscle
- anterior epithelial cells start actin-myosin synthesis
- they move away from anterior epithelium and end in stroma
- connective tissue and capillaries move between the shpincter and anterior epithelium
Name the steps of development of the dilator
actin and myosin appear in the anterior epithelium peripheral to the edge of the developing sphincter
Does the iris dilator have capillaries?
What is the pupillary membrane?
a vascular membrane that covers the pupil in early embryonic development
What is the main function of the embryonic pupillary membrane?
nourish the developing lens
What is the annular vessel's function?
acts as both an artery and a vein
What is the annular vessel connected to?
the primitive choriocapillaris
What is the tunica vasculosa lentis?
a layer of blood vessels that surround the developing lens
What arises from the annular vessels to form part of the tunica vasculosa lentis?
arcades of blood vessels
Where do arcades of the tunica vasculosa lentis receive blood from?
- annular vessels
- two long posterior ciliary arteries
What drains into the annular vessel going away from the primitive lens?
- middle part
- capsulopupillary vessels
- lateral part of tunica vasculaosa lentis
- (all are the hyaloid artery system)
What makes up the posterior tunica vasculosus lentis?
capillaries of the hyaloid arter that nourish the lens
Where do posterior tunica vasculosus lentis (PTVL) blood vessels drain?
straight running vessels of the lateral tunical vasculosus lentis (LTVL)
What is the most complex tunica vasculosus lentis and what does it surround?
- the posterior one (PTVL)
- posterior part of the lens
When does the pupillary membrane atrophy?
about 7th month of the gestation period
What is the last iris structure to develop?
the pupil due to late atrophy of pupillary membrane
What is recorded when a patient has a persisting pupillary membrane?
- could stand for collagen fibers or blood vessels traveling across pupil.