Flashcards in Exam 3 Remington- Embryology Deck (170):
1
What are the reasons for studying the development of the eye?
Adult anatomy explained, histology of ocular tissue, congenital abnormalities explained, congenital anomalies are more prevalent since more premature and high risk babies surviving
2
What are the steps after fertilization?
Fertilization -> Morula (solid mass) -> Blastula -> Inner cell mass (implanted in uterine wall about 10 day) -> Embryonic plate
3
Proliferation
Increase in number of cells
4
Migration
Move to new location
5
Differentiation
Process by which a cell acquires specific functional and structural characteristics
6
Induction
The influence a certain region of tissue or developing structure has on the development of another structure
7
When is the embryonic plate formed?
Day 15
8
Ectoderm
CNS, epidermis of skin, exocrine glands, inner ear, hair and nails
9
Mesoderm
CT, skeletal system, muscle, dermis of skin, circulatory system
10
Endoderm
lining of alimentary and respiratory tracts
11
Neural plate
The ectodermal part of embryonic plate that will become CNS
12
When does thickening occur in ectoderm?
Day 18
13
When is the neural tube formed?
Day 22
14
The neural ectoderm forms the ____
Tube
15
The surface ectoderm covers the ______
Organism
16
Neural crest cells separate from ____ ____
Crest areas
17
What is formed from the neural ectoderm?
RPE, neural retina, optic nerve fibers, neuroglia, epithelium of ciliary body, epithelium of iris, iris sphincter, dilator muscles
18
What is formed from the surface ectoderm?
Lens, corneal epithelium, conjunctival epithelium, epithelium of eyelids, cilia, Meibomian glands, glands of Zeis and Moll, epithelium lining nasolacrimal system
19
What is formed from the neural crest cells?
Corneal stroma (which gives rise to Bowman's layer), corneal endothelium (which gives rise to Descemet's), most of sclera, trabecular structures, uveal pigment cells, uveal CT, ciliary muscle, meninges of optic nerve, vascular pericytes
20
Where is the mesoderm located?
Between ectoderm and endoderm
21
Mesenchyme
Includes both neural crest and mesoderm
22
The neural tube will form _____
CNS
23
When do optic pits become optic vesicles and out-pouches from diencephalon form?
Day 25
24
Optic stalk
Region joining optic vesicle to neural tube constricts
25
Optic cup
Inferior region of the vesicle and stalk begins to invaginate and forms a cleft
26
Optic fissure
Also called fetal fissure or embryonic fissure
27
Coloboma
Incomplete closure of fissure, will result in incomplete formation of certain structures and/or layers
28
What is a thickening in the surface ectoderm?
Lens vesicle
29
What forms the lens plate or placode?
Lens vesicle
30
What gene may be one of the factors that extablishes the lens component of surface ectoderm?
Pax-6
31
An indentation of the lens vesicle forms ___ ___
Lens placode
32
When does the vesicle separate from the surface ectoderm?
Day 33
33
Lens vesicle cells secretes what?
Basal lamina
34
What elongates forming embryonic nucleus?
Posterior lens epithelium
35
What forms secondary lens fibers of the fetal nucleus?
Mitosis at the pre-equatorial zone
36
What are the vessels that enter the globe through the fissure formed from?
Mesenchyme
37
Posterior tunica vasculosa lentis branches from what?
Hyaloid vessels
38
Anterior tunica vasculosa lentis branches from what?
Annular vessel
39
The posterior and anterior tunica vasculosa lentis are joined and nourish the lens during months ____
3-4
40
When are the networks absorbed?
Month 8
41
The hyaloid arterial system is surrounded by ___ ___
Glial tissue
42
The amount of reabsorption of glial tissue influences ____
Extent
43
What occurs in the optic cup?
Proliferation, migration, and differentiation
44
What is the first retinal layer to differentiate?
RPE
45
Neural Retina Proliferative Zone
Contains the cell bodies which will form retinal cells
46
Neural Retina Marginal Zone of His
Located next to basal lamina
47
Inner neuroblastic layer
Contains cells that will become ganglions, amacrines, and Mullers
48
Outer neuroblastic layer
Contains cells that will become photoreceptors, bipolars, horizontals (origin of interplexiform neurons not determined)
49
Transient fiber layer of Chievitz
Area between layers contains no cells
50
When does apoptosis begin?
Month 5
51
What happens in retinal development during month 6?
No further mitosis, differentiation and cell maturation continue
52
The macular area is the thickest retinal area until about ____ months of gestational age and until up to 9 rows of ganglion cells present
6
53
The depression in the macula continues to deepen until when?
15 months
54
What are first to differentiate in the macular area?
Ganglion cells
55
What are cone axons dependent on?
Light stimulation for complete growth of Henles fibers to reach synapses in OPL
56
What does the CRA develop as buds from in month 4?
Hyaloid
57
What does the CRV develop as buds from?
Maxillary vein
58
When is the vasculature complete?
3 months post pardum
59
What does the corneal epithelium develop from?
Surface ectoderm
60
When are ZO evident in the corneal epithelium?
Week 6
61
What does the corneal endothelium develop from?
Develops from neural crest cells in 1st wave mesenchyme
62
What does the corneal stroma develop from?
From neural crest cells in second wave of mesenchyme
63
Where does the sclera form from?
Primarily from the neural crest, in mesenchyme that surrounds optic cup
64
By what months has the sclera surrounded the choroid?
3rd month
65
The sclera usually develops _____ first
Anteriorly
66
Where does the choroid develop from?
Mesenchyme
67
What is the first layer to differentiate of the choroid?
Choriocapillaris
68
The epithelial layers of the ciliary body are from the ____ ___
Optic cup
69
The mesenchymal cells in the ciliary body differentiate forming what two things?
Stroma and muscle
70
When will the annular muscle of Muller be completed?
1st several months after birth
71
What do the iris epithelial layers form from?
Optic cup
72
____ _____ forms from a group of cells that detaches from the anterior iris epithelium
Sphincter muscle
73
Mesenchymal cells differentiate in the iris forming _____ and _____
Melanocytes and fibroblasts
74
When the anterior tunica vasculosa lentis degenerates into what two things?
Minor circle of the iris and stroma
75
_____ ____ forms from cells of third wave of mesenchyme
Pupillary membrane
76
When does the pupillary membrane present?
Month 3-5
77
The pupillary membrane degenerates from month _____
6-8
78
The remnants of the pupillary membrane are incorporated into what two things?
Collarette and anterior border layer
79
Mass of _____ accumulates in the angle area
Mesenchyme
80
Once the trabecular meshwork is formed a continuous sheet of _______ covers it
Endothelium
81
When must the trabecular meshwork break down exposing the meshwork for aqueous drainage to occur?
Month 7-9
82
What does Schlemm's canal develop from?
Veins in the area
83
What is the primary vitreous?
Degenerating hyaloid system becomes Cloquet's canal
84
What is the secondary vitreous?
Mesenchyme, retinal fibrils forms intermediate vitreous
85
What is tertiary vitreous?
Zonules
86
What is the outer layer of the optic nerve?
Forms neuroglial sheath
87
What is the inner layer of the optic nerve?
Cells form glial tissue, other cells vacuolate allowing for passage of ganglion axons
88
_____ ____ fill lumen growing from the globe to the LGN
Ganglion cells
89
Where does myelination begin?
LGN
90
When is myelination completed?
1 month after birth
91
Eyelid buds grow and fuse when?
About 2nd gestational month
92
When do eyelids separate?
5-6
93
What of the eyelids is made of surface ectoderm?
Epithelial layers of the skin and conjunctiva, hair follicles and cilia, Meibomian glands, Zeis glands and glands of Moll
94
What of the eyelids is made of mesenchyme?
Tarsal plates, orbicularis, levator, and tarsal muscle of Muller
95
What part of the orbit has neural crest origin?
Fat and CT
96
What is the position of the orbit at month 3?
180-105 degrees
97
What is the position of the orbit at birth?
71 degrees
98
What is the position of the orbit in adulthood?
68 degrees
99
Muscle cells have ________ origin
Mesodermal
100
Connective tissue has _____ _____ origin
Neural crest
101
The lacrimal gland was once thought to be derived from ___ _____, but now believed to be from ______ _____
Surface ectoderm, neural crest
102
The nasolacrimal system is not fully developed or functioning until what age?
3-4 years
103
All structures of drainage has ______ _____ origin
Surface ectoderm
104
Germinal Period
Day 1-21; rapid cell division, differentiation of primary germ layers, travel down fallopian tubes to uterus where implantation occurs about day 10
105
Embryonic Period
4-8 weeks; differentiation of all major internal and external body structures, vital organs first
106
Fetal Period
9 weeks to birth
107
What happens in the fourth week of the embryonic period?
Cardiovascular system, heart starts beating
108
What happens in the fifth week of the embryonic period?
Eyes, ears, mouth, and nose forming
109
What happens in the 5-8 weeks of the embryonic period?
Limbs, fingers, and toes are webbed
110
What happens in week 12 of the fetal period?
Growth stage, sexual differentiation
111
What happens in week 28 of the fetal period?
Brain wave patterns show active cycles
112
When is the age of viability?
24-28 weeks
113
How long is a normal term?
38 weeks
114
GA 7-8 days
0.1 mm
115
GA 11-12 days
0.2 mm
116
GA 21-24 days
1.5-3.5 mm
117
GA 24-27 days
4.0-9.5 mm
118
GA 5 weeks
10-13 mm
119
GA 6 weeks
14-18 mm
120
GA 7 weeks
19-24 mm
121
GA 8 weeks
25-30 mm
122
GA 3 months
31-70 mm
123
GA 4 months
41-110 mm
124
GA 5 months
111-150 mm
125
GA 6 months
151-190 mm
126
GA 7 months
191-240 mm
127
GA 8 months
241-280 mm
128
GA 9 months
280-320 mm
129
Variation
slight departure from normal, too minor to interfere with function
130
Anomaly
Very different from normal, may interfere with function
131
Aberration
Difference in structure which does not resemble any stage of normal development
132
Arrest
Normal development halted
133
What are the causes of ocular congenital abnormalities
Genetic, environmental, interactions between genetic and environment
134
Teratogens
Any agent which acts on the fetus during intrauterine life, may be chemical (drugs), disease, physical, nutritional
135
What is likely is insult during the germinal period?
Spontaneous abortion
136
What is likely if insult during embryonic period?
Major anomalies or aberrations
137
What is likely if insult during fetal period
Minor anomalies and variation
138
Cyclopia
Single median eye or 2 fused at midline
139
Hypertelorism
Greater than normal distance between orbits
140
Hypotelorism
Less than normal distance between orbits, midbrain often affected
141
Anophthalmia
Absence of ocular tissue derived from optic cup
142
Microphthalmia
Globe and lens small and undeveloped
143
Buphthalmos
Congenital glaucoma, marked distention of eye caused by increase of IOP, cause is often defect in angle structures or persistence of Barkan's membrane
144
What is the outcome of buphthalmos?
Very poor
145
Endothelial compromise in buphthalmos leads to what?
Corneal edema and scarring
146
What happens if there is nerve fiber loss in buphthalmos?
Field loss
147
Ocular albinism
Lack of pigmentation, normal development of sensory retina is influenced by melanin-related agent in RPE, absence of pigment causes retinal abnormalities are present, underdeveloped central retina, fewer rods
148
Megalocornea
Cornea and anterior segment enlarged, may be associated with increased IOP
149
Microcornea
11 or 12 mm, normal size globe, small cornea
150
Mittendorf's dot
Small area of tissue on the posterior lens, no visual implications
151
Congenital cataract
Associated with genetic, metabolic, or infectious agents, viral infection of the mother during the first trimester, effect on VA depends on extent, visually debilitating cataracts, soft CL have been used successfully in infants and IOLs have been used in children as young as 3 years
152
Bergmeister's papilla
A remnant of the glial tissue of the hyaloids system, glial tissue projects from optic nerve head, no visual implications
153
Optic nerve hypoplasia
Optic nerve fails to develop completely, fewer than normal number of axons, failure of ganglions to differentiation, failure of their axons to reach the optic stalk, often associated with CNS developmental problems or endocrine disorders, cognitive difficulties and multiple handicaps are common
154
Persistent hyperplastic primary vitreous
Failure of the hyaloid arterial system to regress, appears as a white retrolental mass, associated with angle closure glaucoma and cataract formation
155
Persistent pupillary membrane
Remnant strands form the pupillary membrane, usually attached to collarette, no visual implications
156
Aniridia
Failure of iris to form
157
What are 3 congenital defects affecting the retina?
Myelinated or medullated nerve fibers, coloboma of internal structures, retinoblastoma
158
Retinal coloboma
Ranges from insignificant chorioretinal defect to complete involvement of interfior retina and choroid, causes VF defect
159
What is the most common malignant tumor in childhood?
Retinoblastoma
160
How frequent are retinoblastomas?
1:17,000- 1:34,000 live births per year, 350 new cases in US per year
161
How does a retinoblastoma occur?
Can be dominantly inherited condition with poor or sporadic penetrance or a new genetic mutation, genetic counseling is mandatory
162
Is retinoblastoma bilateral or unilateral?
Both, bilateral is always inherited
163
Retinoblastoma tumor is often derived from malignant changes in _______
Photoreceptors
164
What is the presenting sign of a retinoblastoma?
White pupillary reflex, the tumors appear as white mass, may seed into vitreous or anterior chamber
165
What are treatment options for retinoblastoma?
Photocoagulation, cryotherapy or radiotherapy, chemotherapy
166
Large tumors or optic nerve involvement require ________
Enucleation
167
What are congenital defects affecting vasculature?
Sturge-Weber syndrome, retinopathy of prematurity
168
Sturge-Weber syndrome
Nevus of skin of face (often called port-wine stain, ocular manifestations include hemangiomas of choroidal BV's, may have diffuse leakage leading to retinal detachment
169
What is retinopathy of prematurity associated with?
Low birth weight and supplemental oxygen therap
170