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BS - Cardiovascular System > Development of the Heart > Flashcards

Development of the Heart Flashcards

1
Q

What is vasculogenesis?

A

Making a blood vessel from scratch

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2
Q

What is involved in vasculogenesis?

A

Differentiation of precursor cells into endothelial cells and the de novo formation of a primitive vascular network

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3
Q

What is angiogenesis?

A

The growth of new capillaries from pre-existing blood vessels

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4
Q

In which week of development does formation of the heart begin?

When is the first contraction of the heart?

A

week 3

The first contraction occurs on day 22

The heart starts to beat as soon as it develops

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5
Q

In how many live births do congenital heart defects occur?

A

5-8 in 1,000 live births

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6
Q

What are the three concentric layers of the heart?

What do they develop from?

A
  1. Epicardium
  2. Myocardium
  3. Endocardium

They develop from the primary or secondary heart field

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7
Q

What layer of the heart is the epicardium?

What else does it form and what is it derived from?

A

It is the outer layer of the heart

It is also the visceral (inner) layer of the pericardium

It is derived from visceral mesoderm

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8
Q

What layer of the heart is the myocardium and what is it derived from?

A

It is the middle layer of the heart

It is derived from the visceral mesoderm overlying the heart tube

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9
Q

What is the endocardium derived from?

What is different from the other layers of the heart?

A

It is derived from the heart tube

It is not specialised do blood cells do not stick to it

If they do, this leads to clots

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10
Q

What is the pericardium and what are its 2 layers?

A

It is the sac in which the heart sits

The outer layer is the parietal pericardium

The inner layer sits on the heart and is the visceral pericardium (epicardium)

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11
Q

In the first stage of vasculogenesis, what is the role of the endoderm?

A

The endoderm induces some cells of the overlying splanchnic mesoderm to differentiate into angioblasts

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12
Q

What are angiogenic cell clusters?

On what day do they form?

A

Specialised cell clusters that will form primary heart fields

They form on day 17

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13
Q

During vasculogenesis, what do the angioblasts differentiate into?

A

Endothelial cells and endocardial tubes

2 endocardial tubes form on day 18

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14
Q

What happens to the endocardial tubes during lateral folding?

A

The endocardial tubes fuse to form the primitive heart tube

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15
Q

After the primitive heart tube has formed, what does the mesoderm do?

A

The visceral mesoderm surrounding the primitive heart tube differentiates to form the myocardium

This is the heart muscle outside of the tube

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16
Q

After the myocardium has formed, what does it secrete?

What is the function of the secretion?

A

It secretes a thick layer of extracellular matrix called cardiac jelly

Cardiac jelly is acellular and important in septation of the heart

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17
Q

What is the role of craniocaudal folding in development of the heart?

A

It brings the developing heart tube into the thorax

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18
Q

During craniocaudal folding, where are the primary heart fields derived from?

What level is this at?

A

Derived from the primitive streak at the cranial end

This is at the level of the oropharyngeal membrane

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19
Q

What is formed from the 3 layers of the heart tube?

A

Endocardium - internal endothelial lining

Myocardium - muscular wall

Epicardium - covers outside of heart and is responsible for formation of coronary arteries

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20
Q

As the heart develops, when do the associated vessels develop?

A

The heart develops with the associated vessels at the same time

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21
Q

In the caudal region of a 4 week embryo, which vessels are present?

A

3 paired veins drain into the tubular heart via the right and left horn of the sinus venosus

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22
Q

What vessels are present in the cranial region of a 4-week old embryo?

A

The cranial region connects to 2 dorsal aortae

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23
Q

What is the first part of the heart tube?

What is the inflow and outflow to this region?

A

Sinus venosus

Arterial outflow is at the cranial end

Venous inflow is at the caudal end

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24
Q

With differential growth of the heart tube, which 5 dilatations become apparent?

A
  1. truncus arteriosus
  2. conus arteriosus
  3. ventricle
  4. atrium
  5. sinus venosus
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25
Q

What is the role of the sinus venosus after differential growth?

A

It is at the caudal end and it receives blood

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26
Q

What do the primitive atrium and ventricle go on to form?

What is different about their position in foetal anatomy?

A

They predominantly form their named structure

The atria are at the caudal end but this changes during cardiac looping

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27
Q

What is the bulbus cordis?

How does this change with time?

A

It is the common outflow tract at the cranial end

It consists of the truncus arteriosus and conus arteriosus

As cells are added, it is differentiated between 2 parts

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28
Q

What is the conus arteriosus and truncus arteriosus?

A

The truncus arteriosus is the outflow tract

The conus arteriosus is the region just before blood reaches the pulmonary valves

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29
Q

On which day does cardiac looping begin?

What is significant about the start of this process?

A

Day 23

The heart starts to fold in preparation for dividing into 4 chambers

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30
Q

During cardiac looping, how does the bulbus cordis move?

A

It moves caudally, ventrally and to the right

As it is a fixed tube, other parts of the tube begin to move with it

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31
Q

How does the primitive ventricle move during cardiac looping?

A

The primitive ventricle is displaced before moving back to the midline

The ventricle starts to swing round in a C-shaped loop

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32
Q

Which part of the heart tube is displaced the most during cardiac looping?

A

The sinus venosus

It swings round the most as it starts in the caudal region and moves towards the cranial region

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33
Q

How does the primitive atrium move during cardiac looping?

A

It displaces cranially and dorsally

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34
Q

How is the apex of the heart formed during cardiac looping?

A

It is formed by the ventricles at the end of cardiac looping

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35
Q

By which week has the sinus venosus largely degenerated?

A

week 5

36
Q

What does the right horn of the sinus venosus form?

A

The sinus venarum

This is the smooth part of the atrium

37
Q

How is the sinus venarum differentiated from the majority of the right atrial wall (where is this derived from?)?

A

The sinus venarum is smooth

The rest of the right atrium is trabeculated and derived from the primitive atrium

38
Q

What is the border between the trabeculated part of the right atrium and the sinus venarum?

A

Crista terminalis

39
Q

From which part of the heart tube are the pectinate muscles and the rough part of the heart formed from?

A

Primitive atrium

40
Q

What does the left horn of the sinus venosus form?

A

The oblique vein of the left atrium and coronary sinus

41
Q

What is the ventricular wall formed from?

A

The majority of the ventricular wall is formed by the primitive ventricle

There is a small contribution from the conus arteriosus

42
Q

What does the conus arteriosus go on to form?

A

The smooth walls of the right and left ventricles which lead into the aorta and the pulmonary trunk

This is the aortic vestibule and the conus arteriosus

43
Q

Where is the aortic vestibule located and what is it?

A

It is on the left side of the heart

It is a smooth part of the ventricle just before the outflow tract (aorta)

44
Q

Where is the conus arteriosus (adult) located and what is it?

A

It is on the right side of the heart

It is a smooth part of the ventricle just before the outflow tract (pulmonary trunk)

45
Q

What part of the ventricle is formed from the primitive ventricle?

A

The trabeculated (rough) walls of the ventricle

This includes the muscular ridges of the trabeculae carneae

46
Q

During further differentiation of the atria, how does the left atrium differ to the right atrium?

A

The right atrium enlarges by incorporating the right sinus horn

The left atrium undergoes remodelling

47
Q

What happens to the left atrium during further differentiation of the atria?

A

An outgrowth of the left atrial wall forms a single pulmonary vein

This branches into left and right pulmonary veins, which bifurcate to form 4 pulmonary veins

48
Q

During which week are the 4 pulmonary veins incorporated into the wall of the left atrium?

What is this process and what does it form?

A

during week 5

This process is intussusception and it forms a small roughened area

49
Q

When does septation of the atria begin?

What is the first stage of this process?

A

At the end of week 4

Septation begins with the formation of the septum primum

50
Q

What is the septum primum?

A

A crescent shaped outgrowth from the dorsal wall

51
Q

What forms from the initial extension of the septum primum?

A

The septum primum extends and the diminishing connection between the left and right sides of the primitive atrium is the foramen primum

This is a slight hole between the atria

52
Q

How are dorsal and ventral endocardial cushions formed?

A

The septum primum extends into the atrium

The endothelium lining the boundary between the atrium and ventricle expands to form the cushions

53
Q

What other component helps to form the dorsal and ventral endocardial cushions?

A

cardiac jelly

54
Q

What happens to the endocardial cushions after they have formed?

A

They fuse in the midline to form the atrioventricular septum

55
Q

What has happened in septation by week 6?

What is the consequence of this?

A

The septum primum has fused with the atrioventricular septum

This obliterates the ostium (foramen) primum

56
Q

In septation, what is the consequence of apoptosis occurring?

A

It occurs in the upper part of the septum primum to form the foramen secundum

57
Q

What happens in septation at the same time as formation of the foramen secundum?

A

A crescent-shaped projection forms from the dorsal wall of the atrium

This is the septum secundum

58
Q

How does the position of the septum secundum relate to the septum primum?

A

The septum secundum develops to the right of the septum primum

59
Q

What is significant about formation of the septum secundum?

A

It does not form a complete partition

The opening left in the septum secundum is the foramen ovale

60
Q

What is the role of the foramen ovale?

A

It allows blood to flow from the right atrium to the left atrium

This allows the lungs to be bypassed in foetal circulation

61
Q

What happens to the septum primum and septum secundum after birth?

A

Pressure pushes the 2 septa together until they eventually fuse

62
Q

What happens to the foramen ovale after birth?

A

It is closed as the 2 septa fuse together

The fossa ovalis is a slight indentation where the foramen ovale once was

63
Q

What are the 2 origins of the interventricular septum?

A
  1. muscular part

2. membranous part

64
Q

How does the muscular part of the interventricular septum form?

what else forms?

Which week does this occur in?

A

The muscular part projects from the floor of the primitive ventricle towards the endocardial cushions

This leaves an interventricular foramen

This occurs at the end of week 4

65
Q

How does the membranous part of the interventricular septum form?

A

The membranous part projects inferiorly from the endocardial cushion

66
Q

During which week does the membranous part of the septum close the interventricular foramen

A

during week 7

67
Q

What does septation of the bulbis cordis lead to?

A

Formation of the aorta and the pulmonary trunk

68
Q

During septation of the truncus arteriosus, what will divide the truncus arteriosus into 2 channels?

A

Endocardial swellings called conotruncal ridges

69
Q

What happens to the conotruncal ridges (swellings) after they have formed?

A

They fuse to form the conotruncal septum

70
Q

What happens to the conotruncal septum and what is significant about this?

A

The conotruncal septum fuses with the interventricular septum

This separates the outflow of the right and left ventricles

71
Q

What pattern of movement is followed when the conotruncal swellings fuse together?

Why?

A

They do not fuse in a straight line - they spiral round each other

This allows the RV to connect with the pulmonary trunk and the LV to connect with the aorta

72
Q

What is the role of neural crest cells in septation of the truncus arteriosus?

A

They help with the spiral formation of the conotruncal septum

73
Q

Which 2 organs is blood shunted away from in foetal circulation and why?

A

Liver and lungs

Mother’s circulation will oxygenate and detoxify the blood

A small amount of blood goes to these organs for their development

74
Q

Which vein carries oxygenated blood from the mother to the foetus?

A

Umbilical vein

75
Q

After passing through the umbilical vein, where does the blood flow?

A

Some enters the liver and the rest enters the ductus venosus

Blood entering the ductus venosus bypasses the liver and enters the inferior vena cava

76
Q

What is the passage followed by foetal circulation as blood enters the heart?

A

The inferior vena cava enters the right atrium

Most blood passes through the foramen ovale into the left atrium

It then enters the left ventricle and aorta

77
Q

What is significant about blood entering the right atrium from the SVC?

What vessel does it travel in?

A

Blood entering the RA from the SVC is poorly oxygenated as it is returning from the lungs

It passes through the ductus arteriosus

78
Q

How does the blood in the ductus arteriosus affect the blood in the aorta?

A

The blood in the ductus arteriosus is deoxygenated

It will reduce the oxygenation of the blood in the aorta

79
Q

What is the ductus arteriosus and what is its purpose in foetal circulation?

A

It connects the main pulmonary artery to the proximal descending aorta

It allows blood from the RV to bypass the lungs

80
Q

What happens to the ductus venosus after birth?

What does it form?

A

Termination of umbilical circulation causes the ductus venosus to close and degenerate

This forms the ligamentum venosum in the adult

81
Q

How does the first breath affect the pulmonary arteries and atria?

A

It causes the pulmonary arteries to dilate and changes the pressure in the atria

82
Q

What will increase the pressure in the left atrium after birth?

A

Blood returning from the lungs

83
Q

What happens to the septum primum and septum secundum after birth?

A

The flimsy septum primum is pushed against the sturdy septum secundum

They fuse to close the foramen ovale

84
Q

What structure does the foramen ovale form in an adult?

A

The fossa ovalis

85
Q

How does the first breath affect the ductus venosus?

A

It causes changes in oxygen saturation in the ductus venosus

This causes it to constrict

86
Q

What does the ductus venosus form in the adult?

A

Ligamentum arteriosum

BS - Cardiovascular System (20 decks)

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