Ocular Development Flashcards
What kinds of things are typically derivatives of surface ectoderm
Surface of body and things that continually change/grow/ proliferate throughout life
What are the layers of the optic cup
- inner layer
- outer layer
- optic fissure
What goes through the optic fissure
Hyaloid artery
What happens if the optic fissure does not close before birth
Coloboma
The nerve fibers that emerge from the retinal ganglion cells in the 6th week travel along
The inner wall of the optic stalk to reach the brain
What happens to the optic stalk in the eighth week
The lumen of the stalk is gradually obliterated by growth of the the retinal ganglion cells that travel along the inner wall of the optic stalk, and by the eight week, the hollow stalk is transformed into the solid optic canal
What are the two sources of vasculariszation of the eye in development
- Choroid layer around the eye
2. Transient hyaloid artery
Where does the hyaloid artery come from
Ophthalmic artery
How does the hyaloid artery gain access to the lentiretinal space
Via the optic fissure on the ventral surface of the optic stalk
What does the hyaloid artery supply
Developing retina and initially the lens
Branches of the hyaloid artery extend over the lens and are known as the
Tunica vasculosa lentis
When do the lips of the optic fissure fuse
By day 37
What happens when the optic fissure closes
Encloses the hyaloid artery and its accompanying vein in TCA canal within the ventral wall of the optic stalk
When is the hyaloid vasculature maximally developed
10 weeks
Lens maturation and hyaloid artery supply
When the lens materus during fetal life and ceases to need a blood supply, the portion of the hyaloid artery that crosses the vitreous body degenerates and is removed by macrophages
What is the hyaloid artery degenerated by
Macrophages
As an adult, the course of the hyaloid artery is marked by a conduit through the vitreous body called the
Hyaloid canal (cloquets canal)
What does the proximal portion of the hyaloid artery become
CRA
Vascularization of the retina as the hyaloid artery
Is regressing and is predominant during the final trimester
What happens when a premie is born with their retinas
The vasculature has not developed yet, so they get retinopathy. Need to be put on oxygen to allow the vessels to mature properly
When does the mesenchymal capsule that surrounds the optic cup differentiate into 2 layers?
Week 6 and 7
What are the two layers that the mesenchymal capsule that surrounds the optic cup differentiate into
- Inner pigmented vascular layer called the choroid
2. Outer, fibrous layer called the sclera
What is the choroid layer homologous to
Pia mater and arachnoid membranes
What is the scler homologous to
Dura mater
What does the choroid develop from
Neural crest cell-derived mesenchyme and mesoderm
The anterior sclera begins as a condensation of __________
Mesenchymal tissue that is continuous with the cornea
What are the 3 tissue origins of the cornea
- Head mesoderm: endothelium
- Neural crest cells: stroma
- Surface ectoderm: outer corneal epithelium
Mesenchyme overlying the lens
Splits into two layers that enclose a new cavity called the anterior chamber of the eye
What is the anterior wall of the anterior chamber continuous with
Sclera
What is the posterior wall of the anterior chamber continuous with
Choroid
This thin remaining layer, called the __________, regresses early in fetal period (between 6-8 months) to form the opening called the pupil
Pupillary membrane
What happens when the pupillary membrane does not break down
Leaves strands that traverse the pupil. The posterior chamber eventually underlies the iris and part of the ciliary body
What does the iris stroma develop from
Mesenchymal tissue of both neural crest and mesodermal origin
The posterior iris epithelium and the circumferential arranged smooth muscle bundles of the pupillary muscles in the iris originate from
The neuroepithelium of the optic cup
Inner layer of the optic cup becomes what portion of the iris
Posteiror border of the iris
Just posterior to the developing iris, the optic cup diffentiates and folds to form the
Ciliary body
Mesenchymal cells that invade the choroid of the ciliary body differentiate to form the _____________, which controls the shape and hence the focusing power of the lens
Smooth muscle bundles of the ciliary muscle
What are eyelids derived from
Surface ectoderm
What is the space between the fused eyelids and the cornea called
Conjunctival sac
When do the eyelids separate
5-7 months
What are the eyelid muscles derived from
Mesoderm
What are the lacrimal glands derived from
Surface ectoderm
When does the lacrimal gland mature
6 weeks after birth
Mittendorfs dot
Never goes away. Remnants of the hyaloid artery stuck to the back of the lens
