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Peds > 5. Embryology- Exam 2 > Flashcards

5. Embryology- Exam 2 Flashcards

1
Q

where does Fertilization occurs

A

ampullary region of the fallopian tube

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2
Q

Sperm + Oocyte =

A

Zygote

–undergoes cell divisions

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3
Q

when does the zygote reach 2 cell stage

A

30 hours post fertilization

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4
Q

when does the zygote reach 4 cell stage

A

40 hours post fertilization

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5
Q

when does the zygote reach 12-16 cell stage

A

72 hours post fertilization

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6
Q

the zygote goes through a Series of mitotic divisions. describe what is happening

A

Cells increase in number

Become smaller with each division

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7
Q

Cells are called

A

Blastomeres

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8
Q

Cells are loosely arranged until what cell stage

A

8 cell stage

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9
Q

After the which cleavage do cells have maximized contact with each other

A

3rd cleavage

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10
Q

After the 3rd cleavage, they start to undergo what

A

compaction

–Cells separate into inner and outer cells

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11
Q

16 cell stage is called a

A

Morula

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12
Q

Morula=

A

Has defined inner and outer cells

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13
Q

Morula Inner cells =

A

inner cell mass (will become the embryo)

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14
Q

Morula Outer cells =

A

outer cell mass (will become the trophoblasts, which will be the placenta)

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15
Q

Morula makes its way into what

A

the uterus

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16
Q

when the Morula enters uterine cavity- Fluid penetrates into the intercellular spaces of the Inner Cell Mass. The spaces become a single cavity called what

A

Blastocele

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17
Q

After the Morula makes its way into the uterus, it Enlarges and becomes what

A

embryo is called a Blastocyst at this point

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18
Q

Blastocyst is comprised of what 3 things? describe them

A
  1. Trophoblast – outer covering. Formed from cells of the outer cell mass. Cells flatten and eventually form the epithelial wall of the blastocyst
  2. Blastocele – Internal fluid filled space
  3. Embryoblast – Inner cell mass. Located at one pole
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19
Q

Of the blastocyst, the Trophoblast and part of inner cell mass will become the ______ while the rest of inner cell mass will become the ______

A

placenta

embryo

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20
Q

how long does the blastocyst remain free in the uterus

A

2 days

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21
Q

when does implantation occur

A

Around day 6 (after fertilization)

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22
Q

describe what happens when implantation occurs

A
  1. Trophoblastic cells over the embryoblast pole penetrate btwn the epithelial cells of the uterine wall.
  2. Blastocyst attaches to uterine epithelium, the endometrium- Oriented so the inner cell mass is near the endometrium
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23
Q

describe the 5 steps to get to implantation

A
  1. Fertilization= 12-24 hours after ovulation
  2. Cleavage= completed 30 hours after fertilization
  3. Morula= 3-4 days after fertilization
  4. Blastocyst= 4.5-5 days after fertilization
  5. Implantation= 6 days after fertilization
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24
Q

at what day is the Blastocyst is partially embedded

A

day 8

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25
Q

when the Blastocyst is partially embedded- The Trophoblast cells over the embryoblast differentiate into what 2 layers? describe them

A
  1. Syncytiotrophoblast – multi-nucleated, outer zone, no cell boundries
  2. Cytotrophoblast – mono-nucleated cells, inner layer, distinct cells
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26
Q

both the Syncytiotrophoblast and the Cytotrophoblast become part of what

A

the chorion (one of the fetal membranes)

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27
Q

the inner cell mass of the blastocyst (embroblast) now differentiates in to what 2 layer? describe

A
  1. Hypoblast layer (Entoderm)= Layer of small cuboidal cells adjacent to the blastocyst cavity
  2. Epiblast layer (Ectoderm)= Layer of high columnar cells adjacent to amniotic cavity
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28
Q

when is the blastocyst completely embedded

A

day 11-12

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29
Q

what happens when the blastocyst completely embedded

A

Cells of the Synctiotrophoblast penetrate deeper into endothelial lining of maternal capillaries. The capillaries are congested and dilated…Called SINUSOIDS

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30
Q

what do the sinusoids cause? what is this the beginning of?

A
  • Causes blood to flow through the trophoblastic system

- Beginning of the uteroplacental circulation

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31
Q

Cytotrophoblast proliferates to form what 2 things? describe them

A
  1. Amnion= Thin Protective membrane that surrounds the developing embryo.
  2. Amniotic Cavity= Space, eventually filled with fluid
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32
Q

what has also started to develop back at day 8

A

Gastrulation

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33
Q

define Gastrulation

A
  • Process for establishing 3 germ layers

- These are the major embryonic tissues from which all tissues and organs of the body develop

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34
Q

with Gastrulation- the inner cell mass differentiates into?

A

Ectoderm
Endoderm
Mesoderm

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35
Q

Gastrulationstarts with the formation of what?

A

the primitive streak on the epiblast

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36
Q

when is the primitive streak clearly visible as a narrow groove

A

day 15-16

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37
Q

describe how the cells of the epiblast migrate to the primitive streak

A

Arrive and become “flask-like”

Detach from epiblast and slip beneath it

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38
Q

epiblast gastrulation: Epiblast is the source of the ______. Inward movement / cause _______

A

germ layers

invagination

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39
Q
  1. Cells displace the hypoblast=Creates ____
  2. Others lie between the epiblast and the new endoderm= Creates _____
  3. Cells remaining in the epiblast= Creates _____
A
  1. Endoderm- layers of inner cell mass that borders the blastocele.
  2. Mesoderm- Lies inbetween the ectoderm and endoderm.
  3. Ectoderm - Layer of cells of the inner cell mass closest to the amniotic cavity
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40
Q

now that gastrulation took place, the 3 germ layers are formed and the amniotic cavity starts to form… the inner cell mass in now called the

A

embryonic disc

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41
Q

the ectoderm becomes what?

A

Outer structures: Skin, teeth, mouth glands, nervous system, some endocrine glands

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42
Q

the mesoderm becomes what?

A

All connective tissue, the muscular, skeletal, lymphatic, and circulatory systems

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43
Q

the endoderm becomes what?

A

Deep structures: Epithelium of digestive tract, respiratory system, bladder, vagina, urethra

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44
Q

when does the Cardiovascular System appear? when does the heart start beating?

A

appears middle of 3rd week

beats after 21 days

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45
Q

when does the Cardiovascular System reach a functional state in comparison to other systems

A

long before any of the other systems

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46
Q

Vascular system develops from what?

A

a simple symmetrical plexus, into an asymmetrical complex system of arteries, veins and capillaries.

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47
Q

what is the size of the embryonic heart in relation to the size of the embryo as compared to an adult heart in an adult size body

A

enormous

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48
Q

when do Progenitor Heart Cells start to develop

A

day 16-18

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49
Q

where do Progenitor Heart Cells lie and how do they move

A
  • Lie in the Epiblast- Adjacent to the cranial end of the primitive streak
  • Move through the streak and into the splanchnic layer of the mesoderm
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50
Q

what do Progenitor Heart Cells form

A

Form a horse-shoe shaped cluster of cells called the Primitive Heart Field (PHF) [collection of cells that have a specific assignment]

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51
Q

Primitive Heart Field is specified on both sides and will become what

A

Atria, LV, RV, Conus Cordis and Truncus Arteriosus

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52
Q

starting with Primitive Heart Field the Conus Cordis and Truncus Arteriosus come from what? when?

A

come from the Secondary Heart field and show up around Day 20-21

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53
Q

Progenitor Heart Cells will form blood islands and cardiac myoblasts. These will form what?

A

blood cells and blood vessels

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54
Q

blood islands unite and form what?

A

a a horse-shoe shaped tube that is Endothelial cell lined and Surrounded by myoblasts

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55
Q

more blood islands appear bilaterally, parallel and close to the midline. What will these form

A

dorsal aortas

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56
Q

how is the Intraembryonic Celom (Body Cavity) formed

A
  • by the joining of small (initially isolated) spaces which appear in the lateral mesoderm
  • Bilateral cavities extend cranially and fuse with each other forming a horseshoe-shaped cavity
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57
Q

what eventually becomes the pericardial cavity

A

Intraembryonic Celom

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58
Q

Heart development starts at the end of the 3rd week of ____

A

gestation

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59
Q

where does heart development of the first blood island occur

A

Occurs in the ventral region of the embryo, inferior to the foregut [in front of the intraembryonic celom]
–Anterior part of the celom will develop the pericardial cavity

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60
Q

how do you know heart development of the first blood island has started

A

Scattered masses of angiogenic cells appear in the mesenchyme derived from PHF

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61
Q

how does Endocardial Tube Formation occur

A
  1. Angiogenic cells form clusters (Blood Islands) which increase in size and number.
  2. Acquire a lumen, unite and form a plexus of blood vessels
  3. From this plexus, bilateral endocardial tubes develop
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62
Q

bilateral endocardial tubes develop- they unite to form what?

A

form a common tube= Primitive Heart Tube

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63
Q

when does the Primitive Heart Tube (single heart tube) begin to beat

A

day 21-22

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64
Q

once the Primitive Heart Tube is formed- how does it start to elongate

A

Cells are added from the secondary heart field to the cranial end of the tube

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65
Q

Primitive Heart Tube elongation is essential for what further development

A

normal formation of part of the RV, the Conus Cordis, the Truncus Arteriosus and for looping

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66
Q

what happens if Primitive Heart Tube elongation “looping” does NOT happen know

A

outflow tract defects form=Abnormalities in Cardiac looping=

  • DORT, VSD, TOF, PA, PS
  • Ventricular inversion (corrected transposition)
  • juxtaposition of the atrial appendages
  • Double outlet right ventricle
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67
Q

while Primitive Heart Tube elongation occurs, other blood islands appear inferior to the endocardial tubes and eventually give rise to what? what will this establish?

A
  • dorsal aortas. Will connect with the endocardial tubes

- Establish the arterial end of the heart

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68
Q

What will the other end of the future endocardial tubes make contact with? what does this establish?

A

the vitelline veins (via the sinus venosus) and establish a venous pole

69
Q

when does the newly formed heart tube starts to bend

A

day 23

70
Q

how does the Cephalic part of the newly formed heart tube bend

A

ventrally, caudally, and to the right

71
Q

how does the Caudal part of the newly formed heart tube bend

A

dorsocranially, and to the left

72
Q

the newly formed heart tube starts to bulge into what

A

the pericardial cavity

73
Q

the newly formed heart tube attaches to what

A

to dorsal wall by mesoderm

74
Q

what happens when the newly formed heart tube attaches to dorsal wall by mesoderm

A

Mesoderm eventually ruptures

Leaves heart tube suspended in pericardial cavity

75
Q

what are the 6 regions of newly formed heart tube know

A 
Dorsal Aorta and Aortic Sac
Bulbus Cordis
Primitive Ventricle
Atrioventricular Sulcus
Paired Primitive Atria
Sinus Venosus
76
Q

Dorsal Aorta and Aortic Sac= know

A

Becomes the common outflow tract

77
Q

Bulbus Cordis= know

A

Primitive RV

78
Q

Primitive Ventricle= know

A

Primitive LV

79
Q

Atrioventricular Sulcus= know

A

Divides atria from ventricles

80
Q

Paired Primitive Atria= know

A

Will form common atria

81
Q

Sinus Venosus= know

A

Eventually forms the coronary sinus and oblique vein of the LA

82
Q

what happens on day 23-28

A

Heart undergoes a series of folding that leads to the formation of the bulboventricular loop

83
Q

during days 23-28, Heart Tube grows rapidly in length, especially what section?

A

the midsection (Bulbus Cordis and Ventricle)

84
Q

during days 23-28, why is heart tube forced to bend

A

Because the two ends are fixed, heart tube is forced to bend in order to adapt itself to the pericardial space

85
Q

during days 23-28, how exactly does the heart tube bend and how is it oriented

A
  • Forms a U-Shape
  • Then Forms an S-Shape
  • Oriented so that the atrium and sinus venosus lie superior to the bulbus cordis, ventricle and dorsal aorta/aortic sac
86
Q

during heart folding, the Atria initially paired and this forms what

A

forms common atrium

87
Q

during heart folding, Atrioventricular unction remains narrow and goes on to form what

A

AV Canal – connects common atrium and ventricle

88
Q

during heart folding, Bulbus Cordis is narrow, except what portion? what will this form?

A

proximal 1/3

–Will form trabeculated part of RV

89
Q

during heart folding, Junction between the ventricle and the bulbus cordis externally is the?

A

bulboventricular sulcus

90
Q

the bulboventricular sulcus remains narrow and is called the

A

primary interventricular foramen

91
Q

during folding of the atrium, Atrial portions of the Heart Tube dilate and form the

A

Common Atrium

92
Q

during folding of the atrium, Atrium “climbs up” the ________ wall and takes the ________ with it

A

dorsal pericardial

Atrioventricular junction

93
Q

during folding of the atrium, the Atrioventricular junction remains narrow. This is now called the _____ and it forms communication btwn what?

A

AV Canal

atrium and the primitive ventricle

94
Q

during folding of the ventricles, Ventricle also dilates. This acquires a?

A

larger lumen

95
Q

during folding of the ventricles, Junction of the ventricle and the bulbus cordis remains narrow. The Junction is now called the?

A

intraventricular foramen

96
Q

after dilation of the atrium and ventricles, we see further dilation in what?

A

bulbus cordis

97
Q

after dilation of the atrium/ventricles.bulbus cordis… At the venous pole, growth proceeds to a point where the expanding common atrium does what?

A

has drawn the originally paired sinus venosus together until it consists of a midportion and right and left horns

98
Q

what happens on heart folding day of 24

A

Diverticula appear

99
Q

Diverticula appear in what two sharply defined areas

A
  1. Along front of endocardial tube
  2. Just proximally and distal to the primary interventricular foramen.
    - -Early embryonic Ventricle - Primitive LV
    - -Proximal 1/3 of bulbus cordis - Primitive RV
100
Q

what is the purpose of Diverticula

A

expand the capacity of the heart

Give them the densely trabeculated appearance

101
Q

from the diverticula, the trabeculae inside the heart leads to what?

A

valves, chordeae tendinae, papillary muscles, and atrioventricular valves.

102
Q

heart folding starting from the top:

A

Aortic arches
truncus arteriosus
conus cordis
bulbus cordis

103
Q

As the primitive atria grow, the truncus arteriosus is positioned in a depression between what?

A

the roof of the right and left primitive atria.

104
Q

entrance to the common atrium=

A

Sinuatrial orifice

105
Q

Sinuatrial orifice (entrance to the common atrium) is flanked on each side by what?

A

valvular folds

106
Q

Sinuatrial orifice Left venous valve fuses with?

A

the atrial septum

107
Q

Sinuatrial orifice Superior part of the right venous valve does what?

A

disappears

108
Q

Sinuatrial orifice Inferior part of the right venous valve becomes what?

A

the valve of the inferior vena cava and the valve of the coronary sinus

109
Q

During atrial septation, the left atrium begins to form what?

A

sprouts of the pulmonary veins that grow towards the lungs.

110
Q

when does cardiac septation occur and how long does it last?

A

occurs on day 27

lasts 10 days (27-37)

111
Q

during the 10 day period during cardiac septation, how much does the embryo grow in length

A

5mm to 16-17mm

112
Q

during cardiac septation, The formation of the cardiac septa occur

A

simultaneously

113
Q

during cardiac septation, are there any changes in external appearance

A

no major changes in external appearance

114
Q

during cardiac septation, at day 27- describe the primitive right and left ventricles

A

primitive right and left ventricles are local widenings of the original heart tube -Connected to each other via narrow channel (Interventricular Foramen) [where septa start to occur]

115
Q

during cardiac septation, Blood reaches primitive LV via

A

small opening from the primitive atria

–AV Canal

116
Q

During ventricular development, what 2 important processes occur simultaneously, that result in the “chamberization” of the ventricles

A
  • -Division of the AV Canal into a Right and Left AV orifice via the endocardial cushions
  • -Ventricular Septation
117
Q

where do Endocardial Cushions develop

A

in the Atrioventricular and Conotruncal regions

118
Q

what do Endocardial Cushions assist in

A

Assist in the formation of the atrial and ventricular (membranous) septa, AV Canals, Valves, Aortic and Pulmonary Channels

119
Q

At the end of week 4, Atrioventricular endocardial cushions appear at the AV Canal. describe them

A

2 lateral AV cushions appear on the right and left side of the canal

120
Q

Anterior and posterior cushions push into the lumen and fuse. What does this result in?

A

Results in the complete division of the canal into right and left AV orifices.
–Final and the end of week 5

121
Q

The role of the endocardial cushions is to:

A
  1. Form a barrier between the atria and ventricles
  2. Right –left division of the canal
    - -The resulting canals are eventually occupied by the mitral and tricuspid valves.
122
Q

what happens at the end of week 4

A

Ventricular Septation

123
Q

The ventricular septum is formed by the outgrowth of what?

A

the muscular ridge at the interventricular foramen

124
Q

when the muscular ridge at the interventricular foramen begins to extend- what happens

A

2 primative ventricles expand

–Medial walls become apposed and merge

125
Q

The ventricular septum grows upward from?

A

the apex of the heart to the base of the heart

126
Q

what happens if the ventricular septum doesnt grow all the way

A

muscular VSD

127
Q

what happens if the ventricular septum doesnt connect to the endocusion

A

membranous VSD

128
Q

Interventricular foramen is the space above the _______. What does it do when the conus septum is complete?

A

membranous septum

Shrinks

129
Q

Outgrowth of tissue from the endocardial cushion along the top of the muscular interventricular septum does what?

A
  • closes the foramen

- Fuses with the abutting part of the conus septum

130
Q

when do the paired atria fuse together for form a common atrium

A

At day 27-28

131
Q

Atrial septation occurs _______ and in _______ with ventricular septation

A

simultaneously

cooperation

132
Q

Atrial septation also lasts approximately

A

10 days

133
Q

during atrial septation, ______ crest grows from the roof of the common atrium

A

Sickle-shaped

134
Q

during atrial septation, the first portion of the crest growing from the roof of the common atrium is the?

A

Septum Primum

135
Q

during atrial septation, the first portion of the crest growing from the roof of the common atrium Extends toward the

A

endocardial cushions in the AV Canal

136
Q

during atrial septation, the first portion of the crest growing from the roof of the common atrium does not connect to endocardial cushions- it leaves a space called the

A

Ostium Primum

137
Q

the Ostium Primum is formed by the?

A

opening between the lower rim of the septum primum and the endocaridal cushions

138
Q

during atrial septation, Extensions of the endocardial cushions grow along the edge of the septum primum, closing the?

A

Ostium Primum

139
Q

Before closure of the Ostium Primum, what happens

A

Apoptosis (cell death) makes perforations in the upper part of the septum primum

  • Forms the Ostium Secundum
  • Allows for blood flow to shunt from the right to the left
140
Q

After fusing with the endocardial cushion, if there is a small residual opening at the ECC, what has developed?

A

ostium primum ASD

141
Q

the Lumen of the Right Atrium expands as a result of what?

A

incorporation of the sinus horns

142
Q

when the Lumen of the Right Atrium expands, what appears?

A

New crest-shaped fold appears= Septum Secundum

143
Q

describe the development of the Septum Secundum

A

Extends downward to the septum in the AV canal
Overlaps with the Ostium Secundum
Remaining hole is called the Foramen Ovale

144
Q

recap: what is the first step to atrial septation

A

Septum primum grows downward from the roof of the common atrium

145
Q

recap: what is the second step to atrial septation

A

Apoptosis of a small superior portion of septum primum occurs during continued downward growth, resulting in a foramen secundum

146
Q

recap: what is the third step to atrial septation

A

The septum secundum then grows downward, covering the foramen secundum

147
Q

recap: what is the fourth step to atrial septation

A

The septum secundum then grows further downward and creates a foramen ovale at the ECC

148
Q

recap: what is the fifth step to atrial septation

A

The two septa together now act as a valve to allow blood to enter the left atrium via the foramen ovale, then the septum secundum

149
Q

By the 5th week, what appears

A

opposing ridges appear in the truncus

150
Q

ridges in the truncus cushions that lie on the right superior wall will grow…

A

distally and to the left.

151
Q

ridges in the truncus cushions that lie on the left inferior wall will grow…

A

distally and to the right

152
Q

both truncus cushions (right and left) will grow towards what?

A

the aortic sac

153
Q

both truncus cushions Twist around each other and eventually fuse to form what

A

the aorticopulmonary septum

-Divides the truncus into aortic and pulmonary channels

154
Q

Similar cushions (of the truncus cushions) appear along the?

A

right dorsal and left ventral walls of the conus cordis

155
Q

the Similar cushions (of the truncus cushions) grow how?

A

Grow toward each other and distally

Unite with the truncus septum

156
Q

Similar cushions (of the truncus cushions) divide what

A

Divides the conus into anterolateral portion (RV outflow) and posteromedial portion (LV outflow)

157
Q

what happens on day 29

A

Partitioning of the outflow tract
-Truncus Arteriosus – Aorta
-Conus Cordis – Pulmonary Artery
(Created by a septum that forms in the outflow tract from these swellings)

158
Q

how do AV valves form? 5 steps

A
  1. Each AV orifice is surrounded by local proliferations of mesenchymal tissue.
  2. Blood hollows out and thins the tissue on the ventricular surface
  3. Valves form
  4. Remain attached to ventricular wall by muscular cords
  5. Muscular tissue degenerates and is replaced by connective tissue over time
159
Q

how do semilunar valves form?

A

Small tubercles found on main truncus swellings

Tubercles hollow out on the upper surface

160
Q

when are Valves are fully developed

A

day 55

161
Q

summary of day 1-2

A

Fertilization

162
Q

summary of day 6-7

A

Implantation of blastocyst into uterine wall

163
Q

summary of day 16-20

A

Appearance of Celom and Blood Islands

164
Q

summary of day 20

A

Endocardial tubes are present and begin fusing

165
Q

summary of day 22

A

Main heart tube begins to beat

166
Q

summary of day 23-28

A

Heart Folding

167
Q

summary of day 27-37

A

Atrial and Ventricular septation and development

168
Q

summary of day 29

A

Outflow tract septation

169
Q

summary of day 55

A

Complete

Peds (17 decks)

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