Embryology PPT 1 and 2 Flashcards

1
Q

day 1

A

fertilization

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2
Q

day 2-3

A

cleavage

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3
Q

day 3

A

compaction

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4
Q

blastocyst formation

A

day 4

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5
Q

implantation begins

A

day 6

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6
Q

how many oocytes at birth

A

2 million

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7
Q

how many oocytes at puberty

A

40,000

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8
Q

how many oocytes ovulated

A

400

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9
Q

__surge causes changes within the ovary and egg for it to rupture

A

LH (luteinizing hormone)

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10
Q

Egg is surrounded by the:

A

Zona pelucida: layer of glycoproteins

Corona radiate: granulosa cells that surround the ovary after ovulation

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11
Q

Egg is swept into

A

oviduct (uterine tube)

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12
Q

Fertilization usually occurs in the

A

ampulla

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13
Q

Enters uterus

A

~ day 4

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14
Q

Implantation into uterine wall begins

A

~ 6th embryonic day

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15
Q

Begins process of cellular division (cleavage)

A

right after fertilization

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16
Q

fertilization steps (8)

A

1.Multiple sperm bind to corona radiate
2. Sperm passes through the corona radiata
3. Sperm binds to a ZP protein in the zona pellucida
Causes release of enzmes allowing it to burrow through ZP (acrosome reaction)
4. The cell membrane of 1 sperm fuses with cell membrane of oocyte
5. Initiates calcium influx causing the release of cortical granules (cortical reaction)
Blocks other sperm from fertilizing egg
6. Completion of 2nd meiotic division of the oocyte
7. Male and female pronuclei form fuse
8. Arrangment of the chromososmes for mitotic cell division

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17
Q

fertilzation usually occurs

A

ampulla of uterine tubes

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18
Q

Zygote is the result of the union of the male and female gametes

A

Restores 46

Maternal and paternal chromosomes are mixed

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19
Q

Repeated mitotic cell divisions results in an increase in

A

cell number (not size)

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20
Q

A cell formed by cleavage of a fertilized ovum is call a

A

blastomere

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21
Q

Blastomeres become __ with division

A

smaller

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22
Q

Early blastomeres are

A

totipotent: capable of giving rise to any cell type

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23
Q

in the 8 cell stage __ begins

A

compaction

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24
Q

Blastomeres tightly align by

A

increased cell adhesion and segregate inside vs. outside

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25
Q

Outer cells become

A

trophoblast – cells that will form placenta

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26
Q

Inner cells will form

A

embryo (inner cell mass)

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27
Q

When there are 16-32 blastomeres, the conceptus is referred to

A

a morula

inner cells and outer cells

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28
Q

morula enters uterus when

A

about 4 days after fertilization

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29
Q

___ are pumped into embryo creating a blastocystic cavity

A

Sodium and water

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30
Q

blastocystic cavity

A
  • Mostly separates the embryoblast and trophoblast

- Embryo is called a blastocyst

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31
Q

blastocyst attaches to endometrium

A

~ 6 days after fertilization,

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32
Q

Prior to implantation, the blastocyst “hatches” from ___

A

zona pellucida (Enzymatically bores a whole and squeezes out)

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33
Q

Early ZP shedding or delayed zygote transport can cause

A

implantation in the wrong location (ectopic pregnancy)

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34
Q

Week 2: days 7-14

A
  • Embryo becomes more deeply embedded within endometrium
  • Development of trophoblast into placenta precursor
  • Formation of bilaminar embryo, amniotic cavity
  • ~ day 10 embyro becomes completely embedded within the endometrium
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35
Q

(~day7) Trophoblast proliferates and differentiates into:

A

cytotrophoblast and syncytiotrophoblast

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36
Q

Cytotrophoblast

A

stem cell population that adds cells to the syncytioblast

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37
Q

Syncytiotrophoblast

A
  • Derived from cytotrophoblast proliferation
  • Cells lose membranes and form a syncytium
  • Located at the embryonic pole (adjacent to embryoblast)
  • ~ day 8, begins invading into the endometrium.
  • Blastocyst becomes completely embedded ~day 10
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38
Q

Synctytiotrophoblast comes into contact with uterine vessels and glands creating a

A

primitive uteroplacental circulation (lacunae filled with maternal blood)

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39
Q

Creates lacunae filled with maternal blood

A

Synctytiotrophoblast

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40
Q

fuse creating a lacunar network

A

Lacunae

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41
Q

Cytotrophoblast form extensions that grow into overlying synctiotrophoblast forming

A

chorionic villi

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42
Q

Villi become penetrated by __ that will eventually form blood vessels

A

extraembryonic mesoderm (week 2 and 3)

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43
Q

Embryoblast differentiate into 2 epithelial layers by

A

day 8

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44
Q

Epiblast:

A

columnar cells adjacent to amniotic cavity (dorsal side of embryo)

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45
Q

hypoblast

A

small cuboidal cells adjacent to exocoelomic cavity (primitive yolk sac)

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46
Q
  • Forms into a bilaminar embryonic disc

- Located between amniotic cavity and the primary umbilical vesicle

A

embryoblast

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47
Q

Amniotic cavity forms within the

A

epiblast

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48
Q

Epiblast cells migrate forming

A

the amnion which encloses the amniotic cavity

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49
Q

Hypoblast migrate and line the blastocystic cavity forming the

A

exocoelomic membrane

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50
Q

Blastocystic cavity referred to as the

A

primary umbilical vesicle (primary yolk sac)

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51
Q

Hypoblast and cytotrophoblast produce

A

extraembryonic mesoderm

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52
Q

Extraembryonic mesoderm proliferates and

A
  • Develops spaces within

- These spaces fuse to form the extraembryonic coelom (chorionic cavity)

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53
Q

precursor to the umbilical cord

A

Fluid filled cavity that surrounds the umbilical vesicle and amnion
Except at connecting stalk

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54
Q

Extraembryonic somatic mesoderm + 2 layers of trophoblast form the

A

chorion

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55
Q

chorion

A

Outermost fetal membrane

Contributes to the placenta

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56
Q

Week 3 Days (14-21) key events

A
  1. Appearance of primitive streak
  2. Development of the notochord and neural induction
  3. Differentiation of 3 germ layers (gastrulation)
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57
Q

Gastrulation

A
  • Process where the bilaminar embryonic disc is converted into a trilaminar embryonic disc
  • Beginning of morphogenesis: the development of the form and structure of organs and parts of the body
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58
Q

Gastrulation gives rise to 3 layers

A

ectoderm
endoderm
mesoderm

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59
Q

ectoderm

A

outside layer, gives rise to skin and nervous tissue

60
Q

mesoderm

A

middle layer, generates most of the muscle, blood and connective tissue

61
Q

endoderm

A

epithelial lining and glands of the gut, lung, urogenital tract

62
Q

Gastrulation starts at the beginning of the 3rd week with the

A

formation of the primitive streak

63
Q

Appearance of primitive streak allow identification of

A

cranial/caudal, dorsal/ventral, left/right, medial/lateral

64
Q

primative streak appears

A

caudally in the medial plane on the dorsal aspect of embryonic disc

65
Q

Epiblast proliferate and migrate toward

A

the median plane of the embryonic disc

66
Q

Epiblast dive within the primitive streak

A

Push away hypoblast forming definitive endoderm

Forms mesoderm in between ectoderm and endoderm

67
Q

Remaining epiblast form the

A

ectoderm

68
Q

the addition of cells to the caudal end

A

elongates the primitive streak

69
Q

Cell proliferation at the cranial end forms the

A

primitive node

70
Q

Primitive node functions as

A

a signaling center

71
Q

Mesoderm is patterned based on where the epiblast pass through the primitive streak

A
Closer to primitive node the more axial in location
Notochord
Paraxial mesoderm
Intermediate mesoderm
Lateral mesoderm
72
Q

Notochordal process

A

Cellular rod that is formed by cell migration cranially from the primitive node/pit

73
Q

Notochordal process formed by when

A

day 20

74
Q

The notochord: defines

A

embryo axis and provides support

75
Q

Neurulation:

A

formation of the neural tube

76
Q

Notochord induces overlying ectoderm to thicken forming the

A

neural plate

77
Q

Neural plate inviginates to form

A

neural groove with lateral neural folds

78
Q

week 4 neurulation

A

Neural folds fuse forming the neural tube

Neural tube separates from overlying ectoderm

79
Q

folding and clousre of the neural platate first begins in

A

the cervical region “zips” up toward the head and down toward the tail

80
Q

anterior neuropore closes

A

day 25

81
Q

posterior neuropore closes

A

day 28

82
Q

Raschischisis

A

failure of neural tube folding

83
Q

Anencephaly

A

failure of anterior neuropore closure

84
Q

Spina bifida:

A

failure of posterior neuropore closure (other causes

85
Q

Group of cells that arise in the ectoderm at the margins of the neural plate

A

Neural Crest cells

86
Q

Neural Crest cells

form a flattened mass on the __ aspect of neural tube

A

dorsolateral

87
Q

Detach from the neural tube and become migratory

A

neural crest cells

88
Q

neural crest cells contribute to:

A
  1. Neurons of the spinal ganglia, ANS ganglia, cranial nerve ganglia
  2. Pseudounipolar sensory neurons and post synaptic neurons of ANS
  3. Enteric ganglia (gut)
  4. Melanocytes
  5. Schwann cells
  6. Adrenal chromaffin cells
  7. Pia and arachnoid
  8. Parafollicular cells of thyroid gland
  9. Also contribute to heart and face development
89
Q

Intraembryonic mesoderm proliferates between the

A

ectoderm and endoderm

90
Q

3 regions develop from the mesoderm

A

paraaxial
intermeidate
lateral

91
Q

Paraaxial mesoderm

A

Head mesenchyme

Somites

92
Q

Intermediate mesoderm

A

Urogenital organs

93
Q

Lateral mesoderm

A
  • Split by the formation of the intraembryonic coelom
  • Somatic mesoderm (somatopleure): forms the body wall with the ectoderm
  • Splanchnic mesoderm(splanchnopleure): form the gut wall with the endoderm
94
Q

Somites

A

are block-like condensations of paraxial mesoderm that form on the sides of the neural tube

95
Q

Somite pairs begin formation on

A

day 20, progresses in a cranial to caudal pattern

96
Q

42-44 pairs of somites form, most __disappear leaving 37 pairs

A

caudal

97
Q

1st 4 pairs contribute to

A

head

98
Q

8 pairs contribute to the

A

cervical region

99
Q

12 pairs contribute to the

A

thoracic region

100
Q

5 pairs contribute to the

A

lumbar region

101
Q

5 pairs contribute to the

A

sacral region

102
Q

3 pairs contribute to

A

coccyx

103
Q

somites subdivide into

A

sclerotome and dermamyotome

104
Q

Sclerotome

A

forms meninges, vertebrae and ribs

105
Q

Dermamyotome

A

Dermis of the neck and back and muscle

106
Q

dermomyotome differentiate into the

A

dermatome and myotome

107
Q

Myotome splits into:

A

epimere (dorsal)

hypomere (ventrally)

108
Q

epimere

A

Gives rise to epaxial muslces of the back

Deep back muscles

109
Q

hypomere

A

Gives rise to hypaxial muscles
Muscles of the abdominal and thoracic wall
Limb muscles

110
Q

Somatic mesoderm:

A

Lines body wall

111
Q

somatic mesoderm + ectoderm

A

somatopleure

112
Q

Splanchnic mesoderm:

A

Covers endoderm

113
Q

splanchnic mesoderm + endoderm

A

splanchnopleure

114
Q

Coelom

A

body cavity formed by lateral folding of the embryo

115
Q

Lateral folds fuse at the

A

ventral midline

116
Q

Lateral folds result in the formation of the

A

intraembryonic coelom

117
Q

lateral folds eventually divides into the 3 principal body cavities:

A

pericardial, pleural, peritoneal cavities

118
Q

Craniocaudal and lateral folding draw in the yolk sac (like a purse string) and close off the body wall except at the

A

umbilicus.

119
Q

flat trilaminar embryonic disc transforms into

A

cylindrical embryo

120
Q

Ectopia cordis:

A

failure of the thoracic body wall to close

121
Q

Gastroschisis:

A

failure of the abdominal body wall to close

122
Q

Vasculogenesis begins

A

during 3rd week

123
Q

Hemangioblast cells develop in the

A

extraembryonic splanchnic mesoderm of the yolk sac

124
Q

Hemangioblast cells give rise to

A
  • hematopoietic cell progenitors
  • endothelial precursor cells
    (Endothelial cells will surround blood cell aggregates forming blood islands)
125
Q

Yolk sac involved in erythropoiesis until about

A

day 60

126
Q

Differentiating endothelial cells organize into small capillary vessels and fuse to form

A

channels (vasculogenesis) this process vascularizes the yolk sac,, connecting stalk, and chorionic villi

127
Q

Vessels from ___ go out to placenta and also eventually join with blood vessels in the embryo that have arisen from intraembryonic splanchnic mesoderm to establish circulation.

A

extraembryonic mesoderm

128
Q

Intraembryonic vessels begin to develop on

A

day 18

129
Q

Hematogenesis does not begin within the embryo until about

A

the 4th week

130
Q

2 major phases of hematopoiesis:

A
  • Embryonic (weeks 1-4)

- Definitive (week 4-term)

131
Q

Embryonic (weeks 1-4) : blood cells arise from

A

yolk sac extraembryonic mesoderm

132
Q

Definitive (week 4-term):

A

hematopoietic stem cells that arise from extraembryonic and intraembryonic mesoderm will go on to seed the spleen, liver, and then bone marrow with hematopoietic stem cells.

133
Q

major site of fetal hematopoiesis until bone marrow takes over

A

liver

134
Q

Vasculogenesis:

A

blood vessels arise de novo from “hemangioblasts” that develop into blood cells AND vascular tubes

135
Q

Angiogenesis:

A

growth of new blood vessels from existing ones

136
Q

Foregut

A

Trachea, esophagus, stomach, duodenum, liver, and pancreas

137
Q

Midgut

A

Small intestine, ascending colon, proximal 2/3 of transverse colon

138
Q

Hindgut

A

Distal 1/3 of transverse colon, descending colon, rectum, upper anal canal

139
Q

Weeks 4 – 8

A

Critical period of many organ systems

140
Q

Organogenetic period:

A

all main organ systems have begun to develop

141
Q

Major congenital birth defects may result from ___ in weeks 4-8

A

teratogen exposure

142
Q

Teratogen

A

an agent that can disturb the development of an embryo (or fetus)

143
Q

Radiation, drugs, infections, chemicals major effects in weeks

A

4-8

144
Q

What Serves as an important signaling center in the development of the gut, vertebral column and CNS

A

the notochord

145
Q

The notochord degenerates as the vertebrae form, part persist as ___

A

the nucleus pulposus