Development of the heart

Question 1

Where does the cardiogenic mesoderm originally lie>

Answer 1

Cranial end of the developing neural tube

Question 2

From where does the heart develop?

Answer 2

Cardiogenic mesoderm on the lateral plate

Question 3

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

Answer 3

Inflow= vitello umbilliac vein
Outflow= dorsal aorta

Question 4

What happens at day 20 to the heart?

Answer 4

Angiogenic cells coalesce into left and right endocardial tubes

Question 5

What happens at day 21?

Answer 5

Left and right endocardial tubes fuse

Question 6

What has happened at day 22?

Answer 6

Tubes have fused into one

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

Question 7

What is the inflow tract in heart at day 22?

Answer 7

Sinus venosus

Question 8

What is the bulbus cordis (day 22)

Answer 8

Cranial part of heart giving rise to truncus arteriosus

Question 9

What is the truncus arteriosus (day 22)

Answer 9

Intersection of ascending aorta and pulmonary trunk cranially. Infudibulum caudally

Question 10

3 main events that occur on day 28?

Answer 10

Septum formation in atrioventricular canal
Atrial partioning
Ventricle formation

Question 11

Describe the process of septum formation in atrioventricular canal

Answer 11

• 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

Question 12

What are endocardial tissues

Answer 12

Swellings of mesenchymal tissues that appear in walls of canal

Question 13

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

Answer 13

For better communication with the ventricles

Question 14

How does atrial partitioning begin?

Answer 14

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

Question 15

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

Answer 15

Perforations appear producing the ostium secundum (second opening)

Question 16

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

Answer 16

Foramen ovale

Question 17

What acts as a valve over the foramen ovale?

Answer 17

Septum primum

Question 18

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

Answer 18

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

Question 19

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

Answer 19

Atrial septum

Question 20

What is the ventricular septum made of?

Answer 20

Fusion of muscular and membranous septum

Question 21

Where does muscular interventricular septum develop from?

Answer 21

Floor of primordial ventricle

Question 22

Where does membranous interventricular septum develop from?

Answer 22

Endocardial tissues

Question 23

When does the interventricular foramen close?

Answer 23

Week 7

Question 24

After day 28, what is the outflow tract?

Answer 24

Aorta and pulmonary tract which is known as truncus arteriosus

Question 25

Describe how the outflow tract is repositioned after day 28

Answer 25

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

Question 26

How is pulmonary flow different in the foetus?

Answer 26

It is decreased

Question 27

Role of foramen ovale in the foetus

Answer 27

Shunts highly oxygenated blood from right to left atrium

Question 28

Role of ductus arteriosus

Answer 28

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

Question 29

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

Answer 29

Increased resistance | Decreased flow

Question 30

How saturated in the blood passing through the ductus arteriosus

Answer 30

Moderately

Question 31

What is the ductus venosus

Answer 31

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

Question 32

How oxygenated in blood passing through ductus venosus

Answer 32

Highly

Question 33

What happens to the umbilical vein at birth?

Answer 33

Becomes ligamentum teres | Mesentery becomes falciform ligament

Question 34

What happens to the ductus venosus at birth?

Answer 34

Constricts so all blood passes through the hepatic sinusoids

Question 35

How/ why does the foramen ovale close at birth

Answer 35

-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

Question 36

What does the foramen ovale become once closed

Answer 36

Fossa ovalis

Question 37

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

Answer 37

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

Question 38

What does ductus arteriosus become once birth?

Answer 38

Ligamentum arteriosum

Question 39

What is thought to reopen ductus arteriosus

Answer 39

Prostagladin E2

Question 40

What is a cyanotic heart defect

Answer 40

Defect where oxygenated and deoxygenated blood mix

Question 41

What is an acyanotic heart defect

Answer 41

Narrow valves/ vessels increase heart workload

Question 42

Name 3 main cyanotic heart defects

Answer 42

Tetralogy of fallot Persistent truncus arteriosus Transposition of great vessels

Question 43

How is tetralogy of fallot characterise

Answer 43

Hypercyanotic episodes (fainting)

Question 44

4 lesions involved in tetralogy of fallot

Answer 44

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

Question 45

What is persistent truncus arteriosus?

Answer 45

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

Question 46

What is transposition of great vessel?

Answer 46

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

Question 47

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

Answer 47

Left (or left to right shunt)

Question 48

How common are atrial septal defects?

Answer 48

7:10,000 births

Question 49

Where specifically are atrial septal defects

Answer 49

Septum primum and secundum

Question 50

What changes in circulation arise to atrial septal defects?

Answer 50

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

Question 51

Symptoms of atrial septal defects

Answer 51

Originally asymptomatic until 3rd decade | Exercise intolerance, fatigue

Question 52

Treatment of atrial septal defect

Answer 52

Probe via foramen ovale from one atrium to the other

Question 53

What shunt is present in ventricular septal defect?

Answer 53

left to right

Question 54

What % of all heart defects are ventricular septal defects

Answer 54

25%

Question 55

How many ventricular septal defects close spontaneously

Answer 55

30-50%

Question 56

What is the result of a small patent ductus arteriosus

Answer 56

No increased risk of heart failure | Increased risk endocarditis

Question 57

What is the result of a large patent ductus arteriosus

Answer 57

INcreased blood flow through preventing closure

Question 58

Treatment of patent ductus arteriosus?

Answer 58

Prostaglandin inhibitor

Question 59

What is coarcation of aorta

Answer 59

Constriction of aorta

Question 60

What happens in preductal coarcation of aorta?

Answer 60

Ductus arteriosus persists allowing blood flow

Question 61

What happens in postductal coarcation of aorta?

Answer 61

Collateral circulation must be established for circulation

Question 62

On day 21 what is forming the primitive myocardium

Answer 62

Mesoderm from the foregut

Question 63

How does blood from from baby to placenta

Answer 63

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

Question 64

How does blood go from the placenta to the baby

Answer 64

Oxygented, high pressure blood via the umbilican veins

Question 65

What happens to umbilical arteries after birth

Answer 65

Constrict