Exam 3 Remington- Embryology Flashcards Preview

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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

Retinopathy of prematurity

Exposure to UV light may be a factor, in premature infant retinal vasculature is poorly developed, fibrotic changes can lead to dragging of the nasal vessel temporarily causing retinaldetachment, 90% of the cases do not progress to this stage