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Yr 2 - Cardiology System > Development of Heart > Flashcards

Development of Heart Flashcards

1
Q

How is the heart slightly twisted in situ?

A

Would predominantly see right side as left side predominantly towards posterior

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2
Q

When does formation of heart begin?

A

Week 3

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3
Q

When is first contraction of heart?

A

Day 22

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4
Q

What are the 3 layers of the heart?

A

Epicardium Myocardium Endocardium

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5
Q

What is the epicardium? What is it derived from?

A

Protective outer layer of heat BUT visceral (inner) layer of pericardium (heart cavity) Derived from visceral mesoderm

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6
Q

What is the myocardium? What is it derived from?

A

Middle –> goes on to form heart muscles Derived from the visceral mesoderm overlying the heart tube

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7
Q

What is the endocardium? What is it derived from?

A

Inner lining of heart Derived from the heart tube

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8
Q

What is vasculogenesis?

A

Creating blood vessels from scratch

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9
Q

What is angioblast?

A

The embryonic tissue from which blood vessels arise

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10
Q

How are angioblasts formed?

A

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

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11
Q

What do angioblasts then differentiate into?

A

Endothelial cells which form endocardial tubes with overlying myocardial cells

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12
Q

What does the lateral plate mesoderm get split into?

A
  1. Parietal layer
  2. Inner splanchnic (visceral) layer
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13
Q

What does the splanchnic (visceral) layer go on to form?

A

The endocardial tubes and myocardial cells

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14
Q

How is the primitive heart tube formed?

A

Endocardial tubes fuse during lateral folding to form the primitive heart tube

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15
Q

Why does lateral folding occur?

A

Due to the weight of the amniotic sac

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16
Q

Where is the endocardial (primitive heart) tube in relation to the gut tube?

A

Ventral to the gut tube

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17
Q

What does the visceral mesoderm surrounding the primitive heart tube differentiate to form?

A

The myocardium (heart muscle)

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18
Q

What does the myocardium secrete?

A

A thick layer of extracellular matrix (cardiac jelly)

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19
Q

What brings the developing heart tube into the thorax?

A

Craniocaudal folding (head and tail end come into closer proximity)

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20
Q

Describe the 3 layers of the resultant heart tube

A
  1. Endocardium
    - Forming the internal endothelial lining of heart
    - Endocardial tube surrounded by cardiac jelly
  2. Myocardium
    - Forms muscular wall (myocytes)
  3. Epicardium
    - Covering the outside of the heart tube
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21
Q

What is outer layer of heart tube (epicardium) responsible for?

A

Formation of the coronary arteries

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22
Q

What is purpose of cardiac jelly?

A

Is a gelatinous connective tissue separating the myocardium and heart tube endocardium

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23
Q

At the 4th week, what is responsible for the inflow of blood to the primitive heart?

A

The sinus venosus. Right and left sinus horns empty into primitive atrium.

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24
Q

What is the sinus venosus?

A

At caudal end of the developing heart tube. Largely degerates by week 5. Splits into left and right horn.

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25
Q

What does the cranial region connect to in the 4th week?

A

2 dorsal aortae

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26
Q

With further differential growth of the heart tube, what 5 dilations become apparent?

A
  1. Truncus arteriosus
  2. Conus arteriosus
  3. Ventricle

4 . Atrium

  1. Sinus venosus

These develop into the adult structures of the heart

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27
Q

In foetuses, the ventricle and atrium are the wrong way around. How do they change position?

A

Cardiac looping –> bending of the heart tube positions the heart in the left thoracic region and creates the ‘typical’ heart shpe with the atria posterior to the ventricles

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28
Q

How does the bulbus cordis move during cardiac looping?

A

Move caudually, ventrally and right

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29
Q

How does the primitive ventricle move during cardiac looping?

A

Displaced before moving back to midline

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30
Q

How does the primitive atrium move during cardiac looping?

A

Displaces cranially and caudally

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31
Q

When does sinus venosus mostly degenerate by?

A

Largely degenerates by week 5

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32
Q

What does remnants of left horn of the sinus venosus remain as?

A

Forms the oblique vein of the left atrium and coronary sinus (contributes to venous drainage)

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33
Q

What do vast majority of veins drain into?

A

The coronary sinus (except the superior and inferior vena cava that go straight to right atrium)

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34
Q

What does coronary sinus empty into?

A

Right atrium

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35
Q

What does remnants of right horn of sinus venosus remain as?

A

Remains as part of wall of right atrium –> forms smooth walled part of right atrium (sinus venarum)

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36
Q

What is the smoothed wall part of the right atrium called?

A

Sinus venarum

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37
Q

What does the majority of the right atrial wall (not smooth) appear as? Where is it derived from?

A

Appears rough (trabeculated). Dervied from the primitive atrium

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38
Q

How can the smooth (sinus venarum) and rough (trabeculated) parts of right atrial wall be differentiated?

A

Clear border –> crista terminalis

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39
Q

What is the majority of the ventricular wall (roughened) formed by?

A

The primitive ventricle with a small contribution from the conus arteriosus

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40
Q

What forms the smooth walls of the left and right vnetricles?

A

The conus arteriosus

41
Q

What is the smooth part in the aorta called?

A

The aortic vestibule

42
Q

What is the smooth part (of ventricle wall) in the pulmonary trunk called?

A

Conus arteriosus

43
Q

What is the rest of the rough (trabeculated) ventricular wall called?

A

Trabeculae carneae (muscular ridges of ventricle)

44
Q

What emerges from these trabeculae carneae?

A

Papillary muscles

45
Q

During further differentiation of the atria, what happens to the right atrium? What does it incorporate?

A

Incorporates the right sinus horn (into the wall)

46
Q

What happens to the left atrium during further differentiation?

A
  1. An outgrwoth of the left atrial wall forms a single pulmonary vein
  2. Pulmonary vein branches into left and right veins which bifurcate to form 4 pulmonary veins
  3. In week 5, the 4 pulmonary veins are incoportated into the wall of the left atrium
47
Q

What is the process of incorporating the 4 pulmonary veins into the wall of the left atrium called?

A

Intussesception

48
Q

What is the majority of the atrial wall derived from?

A

The primitive atrium

49
Q

When does the primitive atrium start to be divided into left and right atria?

A

At end of week 4

50
Q

How does primitive atrium start to be divided into left and right?

A

Crescent-shaped outgrowth from the dorsal wall called the septum primum

51
Q

As the septum primum extends, it dimishes the connection between the left and right sides of the primitive atrium. What is this called?

A

Foramen primum

52
Q

As the septum primum extends into the atrium, the endothelium lining the boundary between the atrium and the ventricle expands. What does this form?

A

Dorsal and ventral endocardial cushions

53
Q

What are the endocardial cushions outgrowths from?

A

The endocardium

54
Q

What happens to these endocardial cushions? What is then formed?

A

They fuse in the midline to form the atrioventricular septum with 2 channels communicating between the future left atrium and ventricle and right atrium and ventricle (how blood passes from atrium to ventricle in adults)

55
Q

What separates the left and rigt atrium?

A

Septum primum

56
Q

What separates the atrium and ventricle?

A

Endocardial cushions

57
Q

What is the atrioventricular septum?

A

Separates atria and ventricle

58
Q

The septum primum eventually fuses with the atrioventricular septum. What does this cause?

A

Obliteratures the foramen primum and separates the atria and ventricle

59
Q

What is the foramen primum?

A

Connection between the left and right sides of primitive atrium (ostium primum)

60
Q

What is the foramen/ostium secundum? How is it formed?

A

A foramen (hole) in the upper part of the septum primum. Formed by apoptosis

61
Q

What is the septum secundum? How does it form?

A

A 2nd cresent shaped projection forms from the dorsal wall of the atrium. Develops on right side of septum primum.

62
Q

What is the opening in the septum secundum called?

A

The foramen ovale

63
Q

What is the opening in the septum primum called?

A

Foramen secundum

64
Q

What is purpose of these openings in the septum primum and septum secundum?

A

Allows blood to flow from the right atrium to the left atrium and bypass the lungs (foetus does not need to breathe)

65
Q

What is the truncus arteriosus?

A

Dilation at the cranial end

66
Q

How are vessels leaving the heart (aorta and pulmonary trunk) separated?

A

Septation of the truncus arteriosus into the aorta and pulmonary trunk

67
Q

How is the truncus arteriosus divided?

A

Divided into 2 channels by endocardial swellings (conotruncal ridges) that grow out from the outflow tract, spiral and fuse together

68
Q

What do these endocardial swellings fuse to form?

A

The conotruncal septum

69
Q

What does the conotruncal septum separate?

A

Separates the outflow of blood of the left and right ventricles

70
Q

What does the conotruncal septum fuse with?

A

The interventricular septum, forming the membranous part of the interventricular septum

71
Q

How do the conotruncal ridges (swellings) fuse? Why is this required?

A

Not in a straight line but spiral around each other. Required for right ventricle to connect with the pulmonary trunk and left ventricle to connect with the aorta

Separates oxygenated and deoxygenated blood

72
Q

What do the conotruncal swellings contain?

A

Neural crest cells

73
Q

What do neural crest cells do?

A

As neural folds elevate and fuse, the cells at the lateral edge separate from the neural tube (neural crest cells). These migrate laterally and ventrally, dispersing widely and differentiating into a variety of structures throughout the body

Sometimes referred to as 4th germ layer

74
Q

In foetal circulation, why is blood shunted away from the liver and lungs?

A

The mother’s circulation is oxygenating and detoxifying blood

75
Q

How does oxygenated blood pass to the foetus?

A

Through the umbilical cord

76
Q

Where does the oxygenated blood go after reaching the foetus?

A

Some enters the liver, the rest enters the ductus venosus (bypassing the liver) and entering the inferior vena cava and then the right atrium

77
Q

What is the ductus venosus?

A

Allows venous blood to bypass the liver and enter the inferior vena cava and then the right atrium

78
Q

When oxygenated blood reaches the right atrium in foetuses, what then happens?

A

Most of the blood passes through the foramen ovale to the left atrium, left ventricle and aorta (bypasses lungs)

79
Q

What is the ductus arteriosus?

A

A patent vessel in fetal circulation between the pulmonary trunk and aorta. A shunt in fetal circulatory system so blood can bypass the lungs. Closes shortly after birth to form the ligamentum arteriosum

80
Q

After birth, why do these shunts have to be closed off?

A

As blood needs to be sent to/from the lungs

81
Q

How is the ductus arteriosus closed off?

A

Increase in pressure in atria (due to blood now passing to lungs) causes septum primum to flap against septum secundum. This closes off the shunt between the atria and the ductus arteriosus to form the ligamentum arteriosum

82
Q

What causes the ductus venosus to close and degenerate? What does it become?

A

Termination of the umbilical circulation.

Ligamentum venosum in adults

83
Q

How is the foramen ovale closed?

A

During first breath:

  1. Pulmonary arteries dilate
  2. Changes pressure in atria
  3. Blood returning from lungs increases pressure in left atrium and flimsy septum primum is pushed against the sturdy septum secundum
  4. This closes the forament ovale to become the fossa ovalis in adults
84
Q

What is the ligamentum arteriosum?

A

A small ligament that is the remnant of the ductus arteriosus formed within three weeks after birth

85
Q

The heart begins to develop near the head of the embryo. What is this area called?

A

Cardiogenic area

86
Q

Following signals from the underlying endodermm what does the cardiogenic area begin to form?

A

2 strands called the cardiogenic cords

87
Q

What happens as the cardiogenic cords develop?

A

A lumen rapidly develops within them and they become endocardial tubes

88
Q

What do the 2 endocardial tubes fuse together to form?

A

A single primitive heart tube

89
Q

When are cardiogenic cords called endocardial tubes?

A

Once lumen forms within

90
Q

What is the ductus venosus?

A

Shunts a portion of umbilical vein blood flow directly to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver.

91
Q

What is a serous membrane made of?

A

The thin membrane is made up of mesothelium tissue which originates from the mesoderm

92
Q

What is a serous membrane?

A

a thin membrane that lines the internal body cavities and organs such as the heart, lungs, and abdominal cavity

93
Q

What is the purpose of a serous membrane?

A

The serous membrane allows for frictionless movement in a number of vital organs.

94
Q

What is the epicardium?

A

a serous membrane that forms the innermost layer of the pericardium

95
Q

What is the function of the epicardium?

A
  • A thin layer of elastic connective tissue and fat that serves as an additional layer of protection from trauma or friction for the heart under the pericardium
  • Contains the coronary blood vessels, which oxygenate the tissues of the heart with a blood supply from the coronary arteries
96
Q

What is the difference between endothelial and epithelial cells?

A

epithelial cells line both internal surfaces and external surfaces of the body whereas endothelial cells line the internal surfaces of the components of the circulatory system

97
Q

What is the conotruncal septum?

A

Separates the truncus cordis into pulmonary trunk and aorta (formed as 2 endocardial swellings spiral and fuse together)

98
Q

What is the conotruncal septum formed from?

A

From neural crest (conotruncal swellings contain neural crest cells)

Yr 2 - Cardiology System (25 decks)

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