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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
What is the role of the sinus venosus after differential growth?
It is at the caudal end and it receives blood
26
What do the primitive atrium and ventricle go on to form? What is different about their position in foetal anatomy?
They predominantly form their named structure The atria are at the caudal end but this changes during cardiac looping
27
What is the bulbus cordis? How does this change with time?
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
28
What is the conus arteriosus and truncus arteriosus?
The truncus arteriosus is the outflow tract The conus arteriosus is the region just before blood reaches the pulmonary valves
29
On which day does cardiac looping begin? What is significant about the start of this process?
Day 23 The heart starts to fold in preparation for dividing into 4 chambers
30
During cardiac looping, how does the bulbus cordis move?
It moves caudally, ventrally and to the right As it is a fixed tube, other parts of the tube begin to move with it
31
How does the primitive ventricle move during cardiac looping?
The primitive ventricle is displaced before moving back to the midline The ventricle starts to swing round in a C-shaped loop
32
Which part of the heart tube is displaced the most during cardiac looping?
The sinus venosus It swings round the most as it starts in the caudal region and moves towards the cranial region
33
How does the primitive atrium move during cardiac looping?
It displaces cranially and dorsally
34
How is the apex of the heart formed during cardiac looping?
It is formed by the ventricles at the end of cardiac looping
35
By which week has the sinus venosus largely degenerated?
week 5
36
What does the right horn of the sinus venosus form?
The sinus venarum This is the smooth part of the atrium
37
How is the sinus venarum differentiated from the majority of the right atrial wall (where is this derived from?)?
The sinus venarum is smooth The rest of the right atrium is trabeculated and derived from the primitive atrium
38
What is the border between the trabeculated part of the right atrium and the sinus venarum?
Crista terminalis
39
From which part of the heart tube are the pectinate muscles and the rough part of the heart formed from?
Primitive atrium
40
What does the left horn of the sinus venosus form?
The oblique vein of the left atrium and coronary sinus
41
What is the ventricular wall formed from?
The majority of the ventricular wall is formed by the primitive ventricle There is a small contribution from the conus arteriosus
42
What does the conus arteriosus go on to form?
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
Where is the aortic vestibule located and what is it?
It is on the left side of the heart It is a smooth part of the ventricle just before the outflow tract (aorta)
44
Where is the conus arteriosus (adult) located and what is it?
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
What part of the ventricle is formed from the primitive ventricle?
The trabeculated (rough) walls of the ventricle This includes the muscular ridges of the trabeculae carneae
46
During further differentiation of the atria, how does the left atrium differ to the right atrium?
The right atrium enlarges by incorporating the right sinus horn The left atrium undergoes remodelling
47
What happens to the left atrium during further differentiation of the atria?
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
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?
during week 5 This process is intussusception and it forms a small roughened area
49
When does septation of the atria begin? What is the first stage of this process?
At the end of week 4 Septation begins with the formation of the septum primum
50
What is the septum primum?
A crescent shaped outgrowth from the dorsal wall
51
What forms from the initial extension of the septum primum?
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
How are dorsal and ventral endocardial cushions formed?
The septum primum extends into the atrium The endothelium lining the boundary between the atrium and ventricle expands to form the cushions
53
What other component helps to form the dorsal and ventral endocardial cushions?
cardiac jelly
54
What happens to the endocardial cushions after they have formed?
They fuse in the midline to form the atrioventricular septum
55
What has happened in septation by week 6? What is the consequence of this?
The septum primum has fused with the atrioventricular septum This obliterates the ostium (foramen) primum
56
In septation, what is the consequence of apoptosis occurring?
It occurs in the upper part of the septum primum to form the foramen secundum
57
What happens in septation at the same time as formation of the foramen secundum?
A crescent-shaped projection forms from the dorsal wall of the atrium This is the septum secundum
58
How does the position of the septum secundum relate to the septum primum?
The septum secundum develops to the right of the septum primum
59
What is significant about formation of the septum secundum?
It does not form a complete partition The opening left in the septum secundum is the foramen ovale
60
What is the role of the foramen ovale?
It allows blood to flow from the right atrium to the left atrium This allows the lungs to be bypassed in foetal circulation
61
What happens to the septum primum and septum secundum after birth?
Pressure pushes the 2 septa together until they eventually fuse
62
What happens to the foramen ovale after birth?
It is closed as the 2 septa fuse together The fossa ovalis is a slight indentation where the foramen ovale once was
63
What are the 2 origins of the interventricular septum?
1. muscular part | 2. membranous part
64
How does the muscular part of the interventricular septum form? what else forms? Which week does this occur in?
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
How does the membranous part of the interventricular septum form?
The membranous part projects inferiorly from the endocardial cushion
66
During which week does the membranous part of the septum close the interventricular foramen
during week 7
67
What does septation of the bulbis cordis lead to?
Formation of the aorta and the pulmonary trunk
68
During septation of the truncus arteriosus, what will divide the truncus arteriosus into 2 channels?
Endocardial swellings called conotruncal ridges
69
What happens to the conotruncal ridges (swellings) after they have formed?
They fuse to form the conotruncal septum
70
What happens to the conotruncal septum and what is significant about this?
The conotruncal septum fuses with the interventricular septum This separates the outflow of the right and left ventricles
71
What pattern of movement is followed when the conotruncal swellings fuse together? Why?
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
What is the role of neural crest cells in septation of the truncus arteriosus?
They help with the spiral formation of the conotruncal septum
73
Which 2 organs is blood shunted away from in foetal circulation and why?
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
Which vein carries oxygenated blood from the mother to the foetus?
Umbilical vein
75
After passing through the umbilical vein, where does the blood flow?
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
What is the passage followed by foetal circulation as blood enters the heart?
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
What is significant about blood entering the right atrium from the SVC? What vessel does it travel in?
Blood entering the RA from the SVC is poorly oxygenated as it is returning from the lungs It passes through the ductus arteriosus
78
How does the blood in the ductus arteriosus affect the blood in the aorta?
The blood in the ductus arteriosus is deoxygenated It will reduce the oxygenation of the blood in the aorta
79
What is the ductus arteriosus and what is its purpose in foetal circulation?
It connects the main pulmonary artery to the proximal descending aorta It allows blood from the RV to bypass the lungs
80
What happens to the ductus venosus after birth? What does it form?
Termination of umbilical circulation causes the ductus venosus to close and degenerate This forms the ligamentum venosum in the adult
81
How does the first breath affect the pulmonary arteries and atria?
It causes the pulmonary arteries to dilate and changes the pressure in the atria
82
What will increase the pressure in the left atrium after birth?
Blood returning from the lungs
83
What happens to the septum primum and septum secundum after birth?
The flimsy septum primum is pushed against the sturdy septum secundum They fuse to close the foramen ovale
84
What structure does the foramen ovale form in an adult?
The fossa ovalis
85
How does the first breath affect the ductus venosus?
It causes changes in oxygen saturation in the ductus venosus This causes it to constrict
86
What does the ductus venosus form in the adult?
Ligamentum arteriosum

BS - Cardiovascular System (20 decks)

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