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CR 2 > Development of the heart > Flashcards

Development of the heart Flashcards

1
Q

Where does the cardiogenic mesoderm originally lie>

A

Cranial end of the developing neural tube

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2
Q

From where does the heart develop?

A

Cardiogenic mesoderm on the lateral plate

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3
Q

At 20 days, what is the inflow/ outflow of the embryo heart?

A 
Inflow= vitello umbilliac vein
Outflow= dorsal aorta
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4
Q

What happens at day 20 to the heart?

A

Angiogenic cells coalesce into left and right endocardial tubes

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5
Q

What happens at day 21?

A

Left and right endocardial tubes fuse

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6
Q

What has happened at day 22?

A

Tubes have fused into one

Formation of trunctus arteriosus, bulbus cordis, primitie ventricle and primitive atria

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7
Q

What is the inflow tract in heart at day 22?

A

Sinus venosus

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8
Q

What is the bulbus cordis (day 22)

A

Cranial part of heart giving rise to truncus arteriosus

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9
Q

What is the truncus arteriosus (day 22)

A

Intersection of ascending aorta and pulmonary trunk cranially. Infudibulum caudally

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10
Q

3 main events that occur on day 28?

A

Septum formation in atrioventricular canal
Atrial partioning
Ventricle formation

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11
Q

Describe the process of septum formation in atrioventricular canal

A
  • Endocardial tissues appear in walls of canal
  • Grow and fuse to divide canal into L and R antrioventricular canal
  • Tricuspid and mitral valves and parts of atrial/ ventricular septum arise from endocardial tissues
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12
Q

What are endocardial tissues

A

Swellings of mesenchymal tissues that appear in walls of canal

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13
Q

Why is the atrioventricular canal repositioned to thr right on day 28?

A

For better communication with the ventricles

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14
Q

How does atrial partitioning begin?

A

Crescent of tissue called septum primum grows from dorsal wall of atrium towards endocardial tissue
Creates temporary opening called ostrium primum

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15
Q

What happens before the septum primum forms with the endocardial cushion?

A

Perforations appear producing the ostium secundum (second opening)

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16
Q

What does the free edge of the growing septum secundum form?

A

Foramen ovale

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17
Q

What acts as a valve over the foramen ovale?

A

Septum primum

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18
Q

How is the fusing of septum primum and septum secundum bought about?

A

Pressure increases in the left atrium where the pulmonary veins empty causes septum primum to be forced against septum secundum and they fuse

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19
Q

What do you call the fused septum primum and septum secundum?

A

Atrial septum

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20
Q

What is the ventricular septum made of?

A

Fusion of muscular and membranous septum

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21
Q

Where does muscular interventricular septum develop from?

A

Floor of primordial ventricle

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22
Q

Where does membranous interventricular septum develop from?

A

Endocardial tissues

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23
Q

When does the interventricular foramen close?

A

Week 7

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24
Q

After day 28, what is the outflow tract?

A

Aorta and pulmonary tract which is known as truncus arteriosus

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25
Q

Describe how the outflow tract is repositioned after day 28

A

Septum forms 2 pairs of swellings which grow from wall of outflow tract
Bulbar ridges are 2 spiral mesoderm ridges from inner wall of truncus arteriosus and bulbur cordis
These twist to form spiral aortico-pulmonary septum

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26
Q

How is pulmonary flow different in the foetus?

A

It is decreased

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27
Q

Role of foramen ovale in the foetus

A

Shunts highly oxygenated blood from right to left atrium

28
Q

Role of ductus arteriosus

A

Shunts blood from pulmonary trunk to aorta
Protects lungs against circulatory overload
Allows right ventricle to strengthen

29
Q

How does ductus arteriosus change pulmonary blood flow and pulmonary vascular resistance

A

Increased resistance

Decreased flow

30
Q

How saturated in the blood passing through the ductus arteriosus

A

Moderately

31
Q

What is the ductus venosus

A

A continuation of the umbilical vein that goes to inferior vena cava

32
Q

How oxygenated in blood passing through ductus venosus

A

Highly

33
Q

What happens to the umbilical vein at birth?

A

Becomes ligamentum teres

Mesentery becomes falciform ligament

34
Q

What happens to the ductus venosus at birth?

A

Constricts so all blood passes through the hepatic sinusoids

35
Q

How/ why does the foramen ovale close at birth

A

-Decreased flow from the placenta and inferior vena cava leads to lower right atrial pressure
-There is also decreased pulmonary vascular resistance secondary to lung expansion
Increase in pulmonary flow, so increased pressure in left atrium
Causes closure

36
Q

What does the foramen ovale become once closed

A

Fossa ovalis

37
Q

What causes closure of ductus arteriosus? What mediates this closure?

A

Increased pa02 causes closure
Decreased pulmonary resistance, PA pressure falls below systemic pressure and blood flow through DA is dimished
Mediated by bradykinin

38
Q

What does ductus arteriosus become once birth?

A

Ligamentum arteriosum

39
Q

What is thought to reopen ductus arteriosus

A

Prostagladin E2

40
Q

What is a cyanotic heart defect

A

Defect where oxygenated and deoxygenated blood mix

41
Q

What is an acyanotic heart defect

A

Narrow valves/ vessels increase heart workload

42
Q

Name 3 main cyanotic heart defects

A

Tetralogy of fallot
Persistent truncus arteriosus
Transposition of great vessels

43
Q

How is tetralogy of fallot characterise

A

Hypercyanotic episodes (fainting)

44
Q

4 lesions involved in tetralogy of fallot

A

1) Overriding aorta arises directly over septal defect leading to mixing of blood
2) Right ventricular hypertrophy due to high right ventricular pressure
3) Ventricular septal defect
4) Narrow right ventricular outflow

45
Q

What is persistent truncus arteriosus?

A

Single artery/ truncus arises from heart and supplies both aorta and pulmonary artery
Large septal defect below tricuspid valve allows mixing of right and left ventricular blood

46
Q

What is transposition of great vessel?

A

Conotruncal septum fails to follow spiral course
Often ductus arteriosus opens
Baby is born blue

47
Q

Are acyanotic heart defects a problem with right or left heart?

A

Left (or left to right shunt)

48
Q

How common are atrial septal defects?

A

7:10,000 births

49
Q

Where specifically are atrial septal defects

A

Septum primum and secundum

50
Q

What changes in circulation arise to atrial septal defects?

A

Pulmonary hypertension
Increase in pulmonary arterial pressure
Causes shift to right to left shunt
Right ventricular hypertrophy

51
Q

Symptoms of atrial septal defects

A

Originally asymptomatic until 3rd decade

Exercise intolerance, fatigue

52
Q

Treatment of atrial septal defect

A

Probe via foramen ovale from one atrium to the other

53
Q

What shunt is present in ventricular septal defect?

A

left to right

54
Q

What % of all heart defects are ventricular septal defects

A

25%

55
Q

How many ventricular septal defects close spontaneously

A

30-50%

56
Q

What is the result of a small patent ductus arteriosus

A

No increased risk of heart failure

Increased risk endocarditis

57
Q

What is the result of a large patent ductus arteriosus

A

INcreased blood flow through preventing closure

58
Q

Treatment of patent ductus arteriosus?

A

Prostaglandin inhibitor

59
Q

What is coarcation of aorta

A

Constriction of aorta

60
Q

What happens in preductal coarcation of aorta?

A

Ductus arteriosus persists allowing blood flow

61
Q

What happens in postductal coarcation of aorta?

A

Collateral circulation must be established for circulation

62
Q

On day 21 what is forming the primitive myocardium

A

Mesoderm from the foregut

63
Q

How does blood from from baby to placenta

A

Deoxygenated high pressure blood via the umbilical arteries (internal iliac arteries)

64
Q

How does blood go from the placenta to the baby

A

Oxygented, high pressure blood via the umbilican veins

65
Q

What happens to umbilical arteries after birth

A

Constrict

CR 2 (33 decks)

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