Cardiac Embryology Flashcards Preview

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Flashcards in Cardiac Embryology Deck (137):
1

Fertilization occurs in

the ampullary region of the fallopian tube

2

Sperm + Oocyte

= Zygote  undergoes cell divisions

3

Reaches 2 cell stage about

30 hours post fertilization

4

4 cell stage at about

40 hours post fertilization

5

12-16 cell stage at about

72 hours (3 days)

6

Cells are called

Blastomeres

7

Cells are loosely arranged until

8 cell stage

8

cells have maximized contact with each other after

3rd cleavage

9

compaction

Cells separate into inner and outer cells.

10

Morula

16 cell stage

11

morula has defined

inner and outer cells

12

Inner cells =

inner cell mass (will become the embryo)

13

outer cells=

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

14

called blastocyst when

Fluid penetrates into the intercellular spaces of Inner
Cell Mass.  Spaces become a single cavity
 Blastocele

15

Blastocyst is comprised of

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

16

Trophoblast and part of inner cell mass will become

the placenta

17

Rest of inner cell mass will become

the embryo

18

Blastocyst remains free in the uterus for

2 days

19

implantation occurs

Around day 6 (after fertilization)

20

Trophoblastic cells over the embryoblast pole penetrate

between the epithelial cells of the uterine wall.

21

Blastocyst attaches to

uterine epithelium, and subsequently the endometrium

22

blastocyst oriented so

inner cell mass is near the endometrium

23

Blastocyst is partially embedded at

day 8

24

at day 8 blastocyst differentiates into

Syncytiotrophoblast – multi-nucleated, outer zone  no cell boundries
 Cytotrophoblast – mononucleated cells, inner layer  distinctcells
 Both layers become part of the chorion (one of the fetal membranes)

25

ICM differentiates into

Hypoblastlayer  Layer of small cuboidal cells adjacent to the blastocyst cavity
 Epiblastlayer  Layer of high columnar cells adjacent to amniotic cavity

26

blastocyst completely embedded at

Day 11-12

27

day 11-12 cells of Syncytiotrophoblast

penetrate deeper into endothelial lining of maternal capillaries

28

Syncytiotrophoblast capillaries are

congested and dilated
 Called Sinusoids
 Causes blood to flow through the trophoblastic system
 Beginning of the uteroplacental circulation

29

Cytotrophoblast proliferates to form:

Amnion
 Thin Protective membrane that surrounds the developing embryo.
 AmnioticCavity  Space, eventually filled with fluid.

30

Gastrulation – starts at

day 8

31

Gastrulation is the process for

establishing 3 germ layers
 ICM differentiates.  Ectoderm  Endoderm  Mesoderm These are the major embryonic tissues from which all tissues and organs of the body develop.

32

gastrulation starts with the formation of

he primitive streak on the epiblast
 By day 15-16, it is clearly visible as a narrow groove.

33

which cells migrate to primitive streak

Cells of the epiblast

34

source of germ layers

epiblast

35

Inner Cell Mass now called an______ as amniotic cavity starts to form

Embryonic Disc

36

Layer of cells of the inner cell mass closest to the amniotic cavity.

ectoderm

37

layers of inner cell mass that borders the blastocele.

endoderm

38

Lies inbetween the ectoderm and endoderm.

Mesoderm

39

Ectoderm Becomes:

Skin, teeth, mouth glands, nervous system, some
endocrine glands.

40

Endoderm Becomes:

Epithelium of digestive tract, respiratory system, bladder, vagina, urethra

41

Mesoderm Becomes:

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

42

Cardiovascular System appears in the middle of the

3rd week. At this point the embryo is no longer able to survive via diffusion alone.

43

The Cardiovascular System reaches

a functional state long before any of the other systems

44

Vascular system develops from a

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

45

The size of the embryonic heart in relation to the size of the embryo

is enormous compared to an adult heart in an adult size body.

46

progenitor heart cells Lie in

Epiblast. Adjacent to the cranial end of the primitive streak
 Move through the streak and into the splanchnic layer of the mesoderm and form around day 16-18

47

Primitive Heart Field (PHF)

horse-shoe shaped cluster of cells

48

PHF specified on both sides to become the

Atria, LV, RV, Conus Cordis and Truncus Arteriosus

49

secondary ear field consists of and shows up when

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

50

blood island and cardiac myoblasts come from

Progenitor Heart Cells

51

Blood islands unite and form

a horse-shoe shaped tube  Endothelial cell lined
 Surrounded by myoblasts. More blood islands appear bilaterally, parallel and close
to the midline.  Will form dorsal aortas.

52

Intraembryonic Celom (Body Cavity) Formed by the joining

small (initially isolated) spaces
which appear in the lateral mesoderm

53

Intraembryonic Celom (Body Cavity Bilateral cavities extend

cranially and fuse with each other forming a horseshoe-shaped cavity
 Eventually becomes the pericardial cavity

54

Heart development starts at the and occurs in

end of the 3rd week of gestation. the ventral region of the embryo, inferior to the foregut.

55

Scattered masses of angiogenic cells appear

in the mesenchyme derived from PHF

56

blood islands occur in

ventral (in front of) the intraembryonic celom.

57

Anterior part of the celom will develop

the pericardial cavity.

58

Angiogenic cells form

clusters (Blood Islands) which increase in size and number. Acquire a lumen, unite and form a plexus of blood vessels

59

, bilateral endocardial tubes develop from

plexus of blood vessels from blood islands

60

The Endocardial tubes unite to form

a common tube
 Primitive Heart Tube

61

the single heart tube starts to beat.

By Day 21-22

62

Cells are added from the secondary heart field to the

cranial end of the tube

63

If lengthening doesn’t occur, where outflow tract defects
come from

DORT, VSD, TOF, PA, PS

64

Meanwhile, Other blood islands appear inferior to the endocardial tubes
 Eventually give rise to ______ and give rise to ______

dorsal aortas.  Will connect with the endocardial tubes  Establish the arterial end of the heart

65

Other end of the future endocardial tubes will make contact with the

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

66

newly formed heart tube starts to bend on day

23

67

Cephalic part bends

ventrally, caudally, and to the right.

68

Caudal part bends

dorsocranially, and to the left

69

attaches to dorsal wall by

mesoderm

70

Becomes the common outflow tract

Dorsal Aorta and Aortic Sac

71

primitive RV

bulbis cordis

72

primitive LV

primitive ventricle

73

Divides atria from ventricles

atrioventricular sulcus

74

Will form common atria

Paired Primitive Atria

75

Eventually forms the coronary sinus and oblique vein of the LA

sinus venosus

76

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

day 23- 28

77

proximal 1/3 Bulbus Cordis Will form

trabeculated part of RV

78

Junction between the ventricle and the bulbus cordis externally is the

bulboventricular sulcus

79

bulboventricular sulcus

aka primary interventricular foramen

80

Atrial portions of the Heart Tube dilate  Form

common atrium

81

Atrium “climbs up” the ______ and takes the

dorsal pericardial wall  TakesAtrioventricularjunctionwithit

82

Diverticula appear

Along front of endocardial tube
 Just proximally and distal to the primary interventricular foramen

83

These diverticula expand

the capacity of the heart. Give them the densely trabeculated appearance

84

The trabeculae inside the heart leads to

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

85

Abnormalities in Cardiac looping, is responsible for cardiac defects

Ventricular inversion (corrected transposition), juxtaposition of the atrial appendages, and Double outlet right ventricle.

86

the sinus venosus receives blood from the right and left sinus horns during

the 4th week

87

each horn of the sinus venosus receives blood from three veins

Vitelline vein  Umbilicalvein  Common Cardinal vein

88

Communication between sinus and atrium is

wide open

89

Communication between sinus and atrium will eventually______ and is caused by

shift to the right. Caused by shift in blood in venous system  Occurs at about 4-5 weeks.

90

Obliteration of the right umbilical vein and left vitelline vein  Occurs

5th week. Left sinus horn loses importance

91

At week 10 the left common cardinal vein become and all that remains

obliterated
 All that remains of the left sinus horn is the oblique vein of the left atrium and the coronary sinus

92

Shunt of blood left to right enlarges

right sinus horn

93

Right horn and vein are the only communication

between the original sinus venosus and the atrium
 Forms the smooth walled part of the right atrium.

94

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

by valvular folds.

95

left venous valves fuse with

the atrial septum

96

Superior part of the right venous valve

disappears

97

Inferior part of the right venous valve becomes

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

98

During atrial septation, the left atrium begins

to form sprouts of the pulmonary veins that grow towards the lungs.

99

Cardiac Septation
 Starts at _____ and lasts

Day 27
 Lasts 10 days (Day 27-37)

100

the embryo grows from _____ to _______ during septation

5mm to 16-17mm

101

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

Division of the AV Canal into a Right and Left AV orifice via the endocardial cushions
 VentricularSeptation

102

Endocardial Cushions
 Develop in the

Atrioventricular and Conotruncal regions

103

endocardial cushions assist in the formation

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

104

Atrioventricular endocardial cushions appear at the AV Canal.

at the end of week 4

105

The role of the endocardial cushions is to:

Form a barrier between the atria and ventricles  Right –left division of the canal
 The resulting canals are eventually occupied by the mitral and tricuspid valves.

106

End of week 4
 The ventricular septum is formed by the

outgrowth of the muscular ridge at the interventricular foramen.

107

he ventricular septum grows upward from the

apex of the heart to the base of the heart

108

Interventricular foramen is the space above

the membranous septum
 Shrinks when the conus septum is complete

109

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

closes the foramen
 Fuses with the abutting part of the conus septum.

110

he paired atria fuse together for form a common atrium at day

27-28

111

Atrial septation occurs ________ with ventricular septation

simultaneously and in cooperation

112

Atrial septation also lasts approximately

10 days.

113

Sickle-shaped crest grows from

the roof of the common atrium

114

Sickle-shaped crest is first part of

Septum Primum

115

septum primum extends

toward the endocardial cushions in the AV Canal.

116

septum primum does not connect to

endocardial cushions. Leaves a space called the Ostium Primum

117

Ostium Primum
 Formed by the opening between

he lower rim of the septum primum and the endocaridal cushions.

118

Extensions of the endocardial cushions grow

along the edge of the septum primum, closing the Ostium Primum

119

Before closure, Apoptosis (cell death) makes perforations in the ________ and forms the

upper part of the septum primum
 FormstheOstiumSecundum  Allows for blood flow to shunt from the right to the left

120

Lumen of the Right Atrium expands (result of incorporation of the sinus horns)
 New crest-shaped fold appears called

SeptumSecundum

121

septum secundum extends

downward to the septum in the AV canal
 Overlaps with the Ostium Secundum  RemainingholeiscalledtheForamenOvale

122

By the 5th week opposing ridges

appear in the truncus

123

Both cushions grow toward

the aortic sac

124

cushions form

aorticopulmonary septum  Divides the truncus into aortic and pulmonary channels.

125

Similar cushions appear along the right dorsal and left ventral walls of

conus cordis. Grow toward each other and distally  Unite with the truncus septum. Divides the conus into anterolateral portion (RV outflow) and posteromedial portion (LV outflow)

126

Outflow Tract Septation – Day 29

Partitioning of the outflow tract
 Truncus Arteriosus – Aorta  Conus Cordis – Pulmonary
Artery
 Createdbyaseptumthat forms in the outflow tract from these swellings

127

Each AV orifice is surrounded by

local proliferations of
mesenchymal tissue. vBlood hollows out and thins the tissue on the ventricular surface
 Valves form
 Remain attached to ventricular wall by muscular cords  Muscular tissue degenerates and is replaced by connective tissue over time.

128

Semilunar Valves

Small tubercles found on main truncus swellings  Tubercles hollow out on the upper surface

129

Day 1-2:

fertilization

130

day 6-7

Implantation of blastocyst into uterine wall

131

day 16-20

Appearance of Celom and Blood Islands

132

Day 20

Endocardial tubes are present and begin fusing

133

day 22

Main heart tube begins to beat

134

day 23-38

Heart Folding

135

day 27-37

Atrial and Ventricular septation and development

136

Day 29

Outflow tract septation

137

Day 55

complete