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68 Cards in this Set
- Front
- Back
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What are the major structures of the eye?
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-Retina
-Iris -Cornea -Lens |
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What causes these major structures to form?
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Inductive interactions
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Initial primordium of eyes:
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Outgrowth of Diencephalon: Optic Groove
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4 Eye precursors:
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-Surface ectoderm
-Neural ectoderm -Neural crest mesenchyme -Paraxial mesoderm |
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What signals the optic groove to form? What tissue does the optic groove (sulcus) derive from?
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Prosencephalic signaling center - optic groove is from Neural Ectoderm
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First step in forming the eye:
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Optic groove expands and forms Optic Vesicle
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How does the optic vesicle remain attached to brain?
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Via Optic Stalk - it becomes the optic nerve
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What happens to the optic vesicle?
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Folds inward and forms a double layered Optic CUP
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What will the Optic Cup become?
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Retina - 2 layers:
-Neural -Non-neural |
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What is the precursor of the optic groove?
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Neural Ectoderm
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How does the Optic Cup fold and what is the result?
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Assymetrically - thus it leaves an inferior groove called the Choroid Fissure
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What tissue precursor forms the OUTER layers of the eyeball?
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Neural CREST - this mesenchyme surrounds the optic cup.
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How does the Lens Placode develop? From what?
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The Optic Vesicle INDUCES it to form when it contacts SURFACE ECTODERM
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What does the Lens Placode become?
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Lens Pit
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What happens to the Lens Pit?
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It forms a closed Lens Vesicle, and eventually differentiates into LENS.
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What does the Lens Vesicle induce before it differentiates into lens?
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By detaching from surface ectoderm, it causes Surface Ectoderm to thicken -> Corneal Placode
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So what is induced by:
-Diencephelon? -Optic Vesicle? -Lens Vesicle? |
Dienceph = Optic Groove to form
Optic Ves= Lens Placode to form Lens Ves = Corneal Placode to form |
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3 Eye development Abnormalities:
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1. Anophthalmia
2. Cyclopia 3. Synophthalmia |
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Anophthalmia:
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Absence of eye structures
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2 types of Anophthalmia:
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-Primary: only eye; rare; structures around eye normal
-Secondry: Eye AND brain holoprosencephaly |
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What is
-Cyclopia -Synophthalmia |
Cyclopia: 1 eye in 1 orbit
Synophtl: 2 eyes in 1 orbit |
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What are both cyclopia and synophthalmia associated with?
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Holoprosencephaly
Midline facial anomalies |
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2 portions of the Retina:
Boundary between them: |
Neural + Nonneural
Ora Serrata |
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What are the layers of the Optic Cup? What separates them?
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Inner layer
Outer layer -Intraretinal space |
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What does the Choroid Fissure function for?
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An inlet for vascular precursors; it extends into the optic stalk and closes in 7th wk.
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What does the Outer Layer of Optic Cup become?
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Pigmented Epithelium (Retina/Iris)
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What does the Inner Layer of Optic CUp become?
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Everything else
-Nonpigmented Iis -Ciliary body -Iris muscles |
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What is the precursor tissue of the iris muscles?
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Neural crest
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What are the 3 initial layers of the Inner layer?
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-Ventricular
-Intermediate -Marginal |
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In which layers do neurons develop?
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Ventricular - Rods/cones
Intermediate - others |
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When is full visual potential achieved?
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By age 2 yrs
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What causes Congenital Detachment of the Retina?
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Failure of the intraretinal space to close.
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What are the Non-Neural portions of the iris?
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-Ciliary body
-Iris |
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What layers of the optic cup form the ciliary processes?
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Both
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What layer of the optic cup forms the Pigmented Iris?
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Outer
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What layer of the optic cup forms the Iris muscles and Ciliary muscle?
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Neural crest cells infiltrate
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What does the Optic Stalk become?
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The optic nerve - connects to the brain.
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Where does the blood supply to the retina form?
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In the retinal (choroid) fissure
of the optic stalk. |
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What does the lens form from?
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Lens placode - thickening of surface ectoderm
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What causes congenital cataracts?
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Inteference w/ lens development
-Increased PTH -Rubella |
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What induces the lens to form again?
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The optic vesicle.
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What does the Lens vesicle induce to form?
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The cornea
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What tissue forms the Posterior epithelium and Stroma of Cornea?
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Neural crest cells
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What does the ectoderm covering the outside of eyeball and inside of eyelids form?
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Conjunctiva
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What does the Choroid Layer develop from?
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Neural Crest mesenchyme that surrounds the optic cup
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Important features of the Choroid:
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-Continuous w/ Arachnoid/Pia
-Vascularized and Pigmented |
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What does the Sclera develop from?
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Neural Crest mesenchyme surrounding the optic cup (same as the Choroid)
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Important features of the Sclera:
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-Continuous w/ Dura
-External to Choroid |
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So of the layers around the eyeball, which are from Neural Crest? From Surf. Ectoderm?
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Neural Crest: Choroid/Sclera
Surf Ectoderm: Eyelids/Lacrimal apparatus |
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What are the extraocular muscles derived from?
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Paraxial mesoderm - somitomeres 1-3, and 5
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What 5 things in the eye are from Paraxial mesoderm?
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-Extrinsic Ocular muscles
-Vascular endothelium -Fluid draining spaces -Orbital soft tissue (?) -Vitreous body |
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What causes Congenital Glaucoma?
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Abnormal devo of the fluid draining spaces of the eye
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What are the fluid draining spaces of the eye?
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-Vitreous body (primary supplied by hyaloid artery, 2ndry replaces it and is avascular)
-Aqueous chambers (provide for continuous fluid removal) |
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What 2 things supply the developing eye with blood?
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-Hyaloid arterial system
-Choroid vessels (around the optic cup) |
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What is Persistent Pupillary Membrane?
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When the Hyaloid artery doesn't degenerate before birth and leaves vessels in front of the lens.
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What is a Coloboma?
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A notch in one or more ocular structures - usually inferior part of iris in midline
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What causes a Coloboma?
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Failure of the Choroid fissure to completely close
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What causes Congenital Ptosis?
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Failure of the Levator Palpebrae to form - fairly common
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What is Microphthalmos?
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Reduction of the eyeball volume - can range from mild to severe
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What is extremely Severe Microphthalmos called?
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Clinical Anophthalmia
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What is the cutoff point for whether Microphthalmos will result in eyeball deficiency beyond size?
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Week 8 - if problem occurs after this, no visual problems; just a small eye. If before, there will be problems.
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What is Cryptophthalmos?
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Absence of eyelids and a hidden eyeball that is malformed.
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3 things that form from Optic Cup Inner layer:
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-Sensory retina
-Ciliary body (nonpigmented) -Iris (nonpigmented) |
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3 Things that form from Optic Cup Outer Layer:
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-Pigmented retina
-Ciliary body (pigmented part) -Iris (pigmented part) |
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What does the Optic cup develop from?
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Neural ectoderm
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What does the Surface Ectoderm become?
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-Lens
-Lacrimal Gland -Cornea (anterior epithelium) -Conjunctiva Epithelium |
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What does the Neural Crest Mesenchyme surrounding the eyeball become?
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-Sphincter/Dilator Pupillae Mm.
-Ciliary muscle -Sclera -Choroid -Cornea - Stromal cells and Posterior epithelium |
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What does Mesoderm contribute to the eye?
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-Extrinsic ocular muscles
-Vascular endothelium -Vitreous body -Fluid draining spaces -Orbit soft tissues -Iris stroma |
