Development of the CVS

Question 1

What are the 4 main stages?

Answer 1

1. Development of Primordial Heart Tube
2. Looping of the Heart Tube
3. Atrial and Ventricular Septation
4. Development of the Outflow Tract

Question 2

What is this?

Answer 2

Bilateral heart primordia

Question 3

Which part of the lateral plate forms the circulatory system (and other viscera)?

Answer 3

Splanchnic mesoderm

Question 4

How are the two primitive heart tubes formed?

Answer 4

Angiogenic cell islands collect in the lateral plate splanchnic mesoderm, move towards the midline and coalesce

Question 5

Why is the cardiovascular system the first major system to function in the embryo?

Answer 5

Diffusion is not enough to satisfy the growing embryo

Question 6

Where do blood vessels first appear?

Answer 6

In the wall of yolk sac, allantois, connecting stalk and chorion

Question 7

When and where do the angioblastic chords form?

Answer 7

Appear in the 3rd week in the cardiogenic mesoderm

Question 8

What do the angioblastic chords do?

Answer 8

Canalize to form heart tubes

Question 9

How is the primordial cardiovascular system formed?

Answer 9

Tubular heart joins blood vessels in other areas

Question 10

Where is the pericardium derived from?

Answer 10

The intra-embryonic coelom (space between the splanchnic and somatic mesoderm)

Question 11

What part of the pericardium is formed from the somatic mesoderm?

Answer 11

Parietal layer of serous pericardium and fibrous pericardium formed from somatic mesoderm.

Question 12

What is the visceral layer of the serous pericardium formed from?

Answer 12

Splanchnic mesoderm

Question 13

What are the following structures?

Answer 13

Question 14

How many horns does the sinus venosus have?

Answer 14

Two horns

Question 15

Where does each sinus venosus get its venous blood?

Answer 15

The yolk sac (viteline vein)

Placenta (umbilical vein)

Body of the embryo (common cardinal vein)

Question 16

How many aorta exist in the embryo?

Answer 16

2, the adults only have the left one

Question 17

How many aortic arches exist initially?

Answer 17

6

Question 18

What is the truncus arteriosis continuous with?

Answer 18

The aortic sac

Question 19

How is the u shape of the bulboventricular loop formed?

Answer 19

Bulbus cordis and the ventricle grow faster than the other regions forming a U shaped loop

Question 20

What is dextrocardia?

Answer 20

Abnormal cardiac looping

Question 21

How does dextrocardia arise?

Answer 21

Heart tube loops to the left side instead of the right thus coming to lie facing the right.

It is the moset requent abnormality of the heart - •Dextrocardia can be associated with situs inversus (transposition of viscera)

Question 22

When does partitioning of the primordial heart take place?

Answer 22

Around the 27th and 37th days of embryonic development

Question 23

What does the endocardial cushion do?

Answer 23

Separates the right atrioventricular opening from the left atrioventricular opening, forming left and right atrioventricular canals

Question 24

atrial septal defect (ASD)

& ventricular septal defect (VSD) are associated with malfunctinos of development with?

Answer 24

Septum formation

Question 25

Look

Answer 25

Question 26

Label the diagram

Answer 26

Question 27

Label the diagram

Answer 27

Question 28

What is the ostium primum?

Answer 28

The opening between the septum primum and the endocardial cushion

Question 29

Where does the foramen secundum form?

Answer 29

The upper end of the septum primum (cell death)

Question 30

Where does the septum secundum form?

Answer 30

On the right of the septum primum

Question 31

How does the septum secundum grow?

Answer 31

Grows and overlaps the foramen secundum - But septum secundum is incomplete – perforated by oval foramen (foramen ovale)

Question 32

Label the diagram

Answer 32

Question 33

What is the role of the oval foramen before birth?

Answer 33

* Allows most of the blood to pass from the right atrium to the left atrium (non functioning lung) * Prevents the passage of blood in the opposite direction

Question 34

What is the function of the oval foramen after birth?

Answer 34

Normally closes allowing for increased pulmonary blood flow and shift of pressure to the left atrium. Septum primum fuses with the septum secundum

Question 35

What is the oval fossa?

Answer 35

Remnant of foetal oval foramen

Question 36

How does hole in the heart arise?

Answer 36

Non closure - no fusino between the septum primum and the septum secundum

Question 37

What are the 4 clinically significant types of ASD?

Answer 37

A)Foramen secundum defect B)Endocardial cushion defect with foramen primum defect C)Sinus venosus defect D)Common atrium The first two types are more common

Question 38

What is the opening called formed by the muscular ventricular septum?

Answer 38

Interventricular septum

Question 39

How is the membranous interventricular septum formed?

Answer 39

Aorticopulmonary septum rotates and fuses with muscular ventricular septum to form membranous interventricular septum, closing interventricular foramen.

Question 40

What is the role of the endocarial cushions in partitioning?

Answer 40

Separates the atria from ventricles Contributes to atrial septation Contributes to the membranous portion of the interventricular septum

Question 41

When does partitioning of the bulbus cordis occur?

Answer 41

5th week of development

Question 42

How is the aorticopulmonary septum created?

Answer 42

Spiralling of the bulbus cordis and the truncus arteriosis resulting in the formation of aorticopulmonary septum. •This septum divides BC and TA in to aorta and pulmonary trunk

Question 43

What is the most common congenital heart disease?

Answer 43

Ventricular septal defect

Question 44

When does the SA node develop?

Answer 44

During week 5

Question 45

Where is the SA node?

Answer 45

•Adult location of SA node – High in the right atrium near the entrance of the SVC

Question 46

Where do the av node and the bundle of his form?

Answer 46

From cells of AV canal and sinus venosus

Question 47

What is Cot death or sudden infant death syndrome (SIDS) caused by?

Answer 47

Cause – abnormalities of conducting tissue

Question 48

Look

Answer 48

Question 49

Who are more likely to be affected from congenital heart disease?

Answer 49

Males ASD more common in females VSD is more common in males

Question 50

What are the causes of congenital heart disease?

Answer 50

Aetiology - Multifactorial * Rubella infection in pregnency (PDA) * Maternal alcohol abuse (septal defects) * Maternal drug treatment and radiation * Genetic - 8% * Chromosomal – 2% (Down’s and Turner’s syndrome)

Question 51

What is a common cause of cyanotic disease in newborn infants?

Answer 51

Transposition of great vessels

Question 52

How does transposition result in complications?

Answer 52

•Permit exchange of systemic and pulmonary circulation

Question 53

What causes transposition of great vessels?

Answer 53

Failure of aorticopulmonary septum to take a spiral course ## Footnote Defective migration of neural crest cells

Question 54

What are the heart defects associated with the tetralogy of fallot?

Answer 54

1. Pulmonary stenosis (obstruction of right ventricular outflow) 2. Ventricular septal defect (VSD) 3. Dextroposition of aorta (“overriding” aorta) 4. Right ventricular hypertrophy

Question 55

What is the cause of tetralogy of fallot?

Answer 55

Unequal division of the conus due to anterior displacement of aorticopulmonary septum